Glucagon-like peptide-1 analogs activate AMP kinase leading to reversal of the Warburg metabolic switch in breast cancer cells

Breast cancer (BC) is associated with type 2 diabetes mellitus (T2DM) and obesity. Glucagon-like peptide (GLP)-1 regulates post-prandial insulin secretion, satiety, and gastric emptying. Several GLP-1 analogs have been FDA-approved for the treatment of T2DM and obesity. Moreover, GLP-1 regulates various metabolic activities across different tissues by activating metabolic signaling pathways like adenosine monophosphate (AMP) activated protein kinase (AMPK), and AKT. Rewiring metabolic pathways is a recognized hallmark of cancer, regulated by several cancer-related pathways, including AKT and AMPK. As GLP-1 regulates AKT and AMPK, we hypothesized that it alters BC cells' metabolism, thus inhibiting proliferation. The effect of the GLP-1 analogs exendin-4 (Ex4) and liraglutide on viability, AMPK signaling and metabolism of BC cell lines were assessed. Viability of BC cells was evaluated using colony formation and MTT/XTT assays. Activation of AMPK and related signaling effects were evaluated using western blot. Metabolism effects were measured for glucose, lactate and ATP. Exendin-4 and liraglutide activated AMPK in a cAMP-dependent manner. Blocking Ex4-induced activation of AMPK by inhibition of AMPK restored cell viability. Interestingly, Ex4 and liraglutide reduced the levels of glycolytic metabolites and decreased ATP production, suggesting that GLP-1 analogs impair glycolysis. Notably, inhibiting AMPK reversed the decline in ATP levels, highlighting the role of AMPK in this process. These results establish a novel signaling pathway for GLP-1 in BC cells through cAMP and AMPK modulation affecting proliferation and metabolism. This study suggests that GLP-1 analogs should be considered for diabetic patients with BC.

Revealing the tumor suppressive sequence within KL1 domain of the hormone Klotho

Klotho, a 1012 amino acid transmembrane protein, is a potent tumor suppressor in different cancer types. Klotho is composed of two internal repeats KL1 and KL2, and the tumor suppressor activity is primarily attributed to the KL1 domain. Despite its significant role in regulating various cancer-related pathways, the precise mechanism underlying its tumor suppressor activity remains unresolved. In this study, we aimed to identify the sequence responsible for the tumor suppressor function of Klotho and gain insights into its mechanism of action. To accomplish this, we generated expression vectors of truncated KL1 at the C and N-terminal regions and evaluated their ability to inhibit the colony formation of several cancer cell lines. Our findings demonstrated that truncated KL1 1-340 (KL340) effectively inhibited colony formation similar to KL1, while truncated KL1 1-320 (KL320) lost this activity. Furthermore, this correlated with the inhibitory effect of KL1 and KL340 on the Wnt/β-catenin pathway, whereas KL320 had no effect. Transcriptomic analysis of MCF-7 cells expressing the constructs revealed enriched pathways associated with tumor suppressor activity in KL1 and KL340. Interestingly, the α-fold predictor tool highlighted distinct differences in the α and β sheets of the TIM barrel fold of the truncated Klotho constructs, adding to our understanding of their structural variations. In summary, this study identified the 340 N-terminal amino acids as the sequence that possesses Klotho's tumor suppressor activity and reveals a critical role in the 320-340 sequence for this function. It also provides a foundation for the development of Klotho-based therapeutic approaches for cancer treatment.

The use of medical cannabis concomitantly with immune checkpoint inhibitors in non-small cell lung cancer: A sigh of relief?

BACKGROUND

The use of medical cannabis has rapidly increased among cancer patients worldwide. Cannabis is often administered concomitantly with cancer medications, including immune checkpoint inhibitors (ICIs). As the cannabinoid receptors are abundantly expressed and modulate immune cells, it has been hypothesised that cannabis may attenuate the activity of ICIs. We aimed to assess the effect of cannabis on ICIs' efficiency in patients having non-small cell lung cancer (NSCLC).

METHOD

The murine model of CT26 tumour-bearing mice treated with an anti-PD-1 antibody and Δ9-tetrahydrocannabinol (THC) was used to evaluate the interaction between THC and ICIs in vivo. Correlation between use of medical cannabis and clinical outcome was evaluated in a cohort of 201 consecutive metastatic NSCLC patients treated with monotherapy pembrolizumab as a first-line treatment.

RESULTS

Median overall survival (OS) of the mice receiving a control vehicle, THC, anti-PD-1 antibody or their combination was 21, 24, 31 and 54 days, respectively (p < 0.05 for the combination treatment compared to a control vehicle), indicating that THC did not reduce the efficacy of anti-PD-1 therapy. Of 201 NSCLC patients treated with first-line monotherapy pembrolizumab for metastatic disease, 102 (50.7%) patients received licence for cannabis within the first month of treatment. Cannabis-treated patients were younger compared to the cannabis naïve patients (median age 68 versus 74, p = 0.003), with female predominance (62, 60.8% versus 34, 34.3%, p = 0.002) and with more prevailing brain metastasis (15.7% versus 5%, p = 0.013). Similar distribution of histology, smoking status, ECOG (Eastern Cooperative Oncology Group) and programmed death-ligand 1 expression was noted between the groups. Liver metastases were marginally significant (19.6% versus 10.1%, p = 0.058). The most common indication for cannabis was pain (71%) followed by loss of appetite (34.3%). Time to tumour progression was similar for cannabis-naive and cannabis-treated patients (6.1 versus 5.6 months, respectively, 95% confidence interval, 0.82 to 1.38, p = 0.386), while OS was numerically higher in the cannabis-naive group (54.9 versus 23.6 months) but did not reach statistical significance (95% confidence interval 0.99 to 2.51, p = 0.08). In multivariate analyses, we did not identify cannabis use as an independent predictor factor for mortality.

CONCLUSIONS

Preclinical and clinical data suggest no deleterious effect of cannabis on the activity of pembrolizumab as first-line monotherapy for advanced NSCLC. The differences in OS can most likely be attributed to higher disease burden and more symptomatic disease in the cannabis-treated group. These data provide reassurance regarding the absence of a deleterious effect of cannabis in this clinical setting.

The effect of non-oncology drugs on clinical and genomic risk in early luminal breast cancer

BACKGROUND

An effect of non-oncology medications on cancer outcome has been proposed. In this study, we aimed to systematically examine the impact of commonly prescribed non-oncology drugs on clinical risk and on the genomic risk [based on the Oncotype DX recurrence score (RS)] in early breast cancer (BC).

EXPERIMENTAL DESIGN

We collected data on clinical risk (stage and grade), genomic risk (Oncotype DX RS), and on non-oncology medications administered to 1423 patients with estrogen receptor-positive human epidermal growth factor receptor 2-negative BC during the month of their surgery. The influence of various medications on clinical and genomic risks was evaluated by statistical analysis.

RESULTS

Out of the multiple drugs we examined, levothyroxine was significantly associated with a high Oncotype DX RS (mean 24.78; P < 0.0001) and metformin with a low Oncotype DX RS (mean 14.87; P < 0.01) compared with patients not receiving other non-oncology drugs (mean 18.7). By contrast, there were no differences in the clinical risk between patients receiving metformin, levothyroxine, or no other non-oncology drugs. Notably, there was no association between the consumption of levothyroxine and metformin and proliferation marker (Ki67) levels, but both drugs were significantly associated with progesterone-related features, suggesting that they influence genomic risk through estrogen-dependent signaling.

CONCLUSIONS

The results of this study indicate a significant impact of metformin and levothyroxine on clinical decisions in luminal BC, with potential impact on the clinical course of these patients.

Abstract 266: Adaptation of colorectal cancer cells to the brain microenvironment: The role of IRS2

Colorectal cancer (CRC) reflects the fourth most frequent etiology of brain metastasis (BM), with rising incidence. Yet, molecular mechanisms supporting the formation of these lesions from CRC are unknown. We aimed to explore drivers enabling tropism and adaptation of CRC cells to the brain environment and decipher mechanisms facilitating the process. We analyzed the FoundationOne database, which contains genomic alterations data of cancer-related genes in over 16,000 human CRC primary and metastasis samples. Increased prevalence of IRS2 gene amplification was observed in 13% of BM, compared to only 3% of primary tumors or other metastatic sites. IRS2 is a cytoplasmic adaptor mediating effects of insulin and IGF-1 receptors and is involved in more aggressive behavior of different cancer types. In agreement with the genomic data, immunohistochemistry of human clinical samples showed increased expression of IRS2 protein in BM. We constructed an in vitro system mimicking the brain microenvironment using cultured human astrocytes or their conditioned media. Under these conditions, IRS2-overexpressed CRC cells survived better and formed larger 3D spheres. IRS2-silenced CRC cells showed a mirror image. Moreover, in an intracranial CRC BM mouse model, IRS2-overexpressed cells generated larger brain lesions, while silencing IRS2 dramatically decreased tumor outgrowth and extended survival. Interestingly, transcriptomic analysis revealed enrichment of oxidative phosphorylation (OXPHOS) and Wnt/β-catenin pathways by IRS2. Indeed, IRS2-expressing cells showed increased mitochondrial activity and glycolysis-independent viability. Furthermore, IRS2-expressing cells had increased β-catenin transcriptional activity. Interestingly, β-catenin inhibition (using ICG-001) or IRS2 inhibition (using NT219) in IRS2-expressing cells decreased their viability, β-catenin transcriptional activity, and mitochondrial activity, suggesting involvement of IRS2 in modulating OXPHOS through β-catenin. β-catenin is known to confer 5-FU resistance; consequently, we showed that combination of 5-FU and NT219 worked in synergy, inhibited the formation of BM, and extended animal survival. These data reveal, for the first time, the unique genomic profile of CRC BM and imply the IRS2 role in promoting CRC BM. These effects may be mediated, at least in part, by modulation of the β-catenin and OXPHOS pathway. Given the molecular signature described, the approach to patients with BM may be significantly impacted by agents such as NT219.

Citation Format: Inbal Greenberg, Anat Klein, Rachel Grossman, Ethan Sokol, Eilam Yeini, Paula Ofek, Ronit Satchi-Fainaro, Bertrand Liang, Hadas Reuveni, Tami Rubinek, Ido Wolf. Adaptation of colorectal cancer cells to the brain microenvironment: The role of IRS2 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 266.

Abstract 1783: JNK/MDR1 confers chemo-resistance in breast cancer cells carrying estrogen receptor activating mutations

Background: Endocrine therapy is the mainstay treatment for estrogen receptor-α (ER) positive breast cancer (BC) patients. However, all metastatic BC patients develop resistance, which in nearly 40% of patients is due to activating mutations, mostly Y537S and D538G, in the ligand-binding domain (LBD). Tumors harboring these mutations are more aggressive and the patients' prognosis is worse. We hypothesized that refractory response to further treatment lines, i.e, chemotherapy, partially accounts for the worse prognosis. Hence, our goal was to study whether LBD-ER BC cells are resistant to chemotherapy and reveal the mechanism of action.

Methods: We used MCF-7 cells stably expressing WT-ER, Y537S or D538G-ER mutations. Cell proliferation and viability were determined using MTT, methylene blue and colony assays. We evaluated apoptosis by monitoring cleaved-PARP and flow cytometry using Annexin/7AAD staining. MDR1 expression was studied using qRT-PCR and western-blot. JNK/c-Jun pathway was studied by pJNK and cJun expressions, cJun transcriptional activity, ChIP assay and pharmacological inhibition.

Results: LBD-ER cells exhibited higher proliferation and viability and exerted less apoptosis compared to WT-ER cells following treatment with paclitaxel, doxorubicin, and 5-FU. MDR1 expression and JNK pathway activity was higher in D538G cells compared to both WT-ER and Y537S cells. Importantly, inhibition of the JNK pathway, using SP600125 and BI-78D3, lead to decreased MDR1 expression, increased cleaved PARP, and decreased viability in the D538G cells. In addition, our results revealed that JNK increased c-Jun binding activity of the MDR1 gene in the D538G mutated cells.

Conclusions: These results indicate that LBD-ER cells confer resistance to chemotherapy. The mechanisms leading to it are diverse, and we found that in D538G increased JNK pathway activation resulted in elevated MDR1 expression and chemo-resistance. This paves the way to therapies aiming at inhibition the JNK pathway in order to restore chemo-resistance. This study also highlights the marked differences between these seemingly similar mutations, strengthening the necessity to adopt a personalized treatment approach for BC patients who developed endocrine resistance.

Citation Format: Marwa Taya, Keren Merenbakh-Lamin, Tami Rubinek, Ido Wolf. JNK/MDR1 confers chemo-resistance in breast cancer cells carrying estrogen receptor activating mutations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1783.

Real-life daily activity: the impact of misbeliefs on quality of life among cancer patients

Background

While side-effects and health-related quality of life (QoL) are routinely assessed in clinical trials, commonly used tools do not measure patients’ ability to maintain normal daily activities. QoL can be severely affected directly by the disease, the treatment side-effects and by personal and societal misconceptions promoting avoidance from activities perceived as dangerous for cancer patients. We examined practices of actively treated patients with cancer.

Methods

A questionnaire was designed, assessing daily activities (11 items) and dietary limitations (7 items) distributed between October and December 2019 (before the coronavirus pandemic) among patients treated at the Oncology Division of Tel Aviv Sourasky Medical Center.

Results

The study population comprised 208 patients who participated in the survey. The majority reported at least one social-environmental avoidance or dietary limitation (136, 65% and 120, 57.7%, respectively), including abstaining from social contact, avoiding pets, public domains, traveling and maintaining dietary constraints. Adoption of these measures was not associated with clinical, demographic factors and treatment type. The major sources guiding restrictions came from advice of non-medical personnel (55.7%), the Internet (7.2%) and personal choice by the patients themselves (24%).

Conclusions

Most cancer patients reported compromised daily activities, which are likely attributed to misbeliefs about disease and treatment, and have a deleterious impact on QoL, in its wider sense, namely, the ability to conduct a full and meaningful life. These findings call for the development and implementation of tools examining patients’ real-life activity, beyond side-effects or health-related QoL (HRQoL). We propose this assessment as an integral part in the evaluation of new drugs and technologies and as an additional endpoint in pivotal clinical trials.

•

Side-effects and HRQoL routinely assessed in clinical trials do not fully measure patients’ maintenance of daily activities.

•

We developed a questionnaire examining daily practices and implications of misbeliefs among actively treated cancer patients.

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Most patients reported compromised daily activities, affecting QoL in its wider sense: conducting a full and meaningful life.

•

These findings call for the development and implementation of tools examining patients’ real-life activity, beyond HRQoL.

•

We propose accounting for a more comprehensive assessment of QoL, and patient health care education dispelling misbeliefs.

Genomic alterations drive metastases formation in pancreatic ductal adenocarcinoma cancer: deciphering the role of CDKN2A and CDKN2B in mediating liver tropism

Metastases are often the direct cause of death from pancreatic ductal adenocarcinoma (PDAC). The role of genomic alterations (GA) in mediating tropism and metastasis formation by PDAC cells is currently unknown. We aimed to identify GAs predisposing colonization of PDAC cells to the liver and decipher mechanisms enabling this process. In order to reveal specific genes, we studied the frequency of GA in 8,880 local and 7,983 metastatic PDAC samples. We observed differential pattern of GA in the local tumor and specific metastatic sites, with liver metastases characterized by deletion of CDKN2A/B (encoding p16/p15, respectively). The role of CDKN2A/B in promoting liver metastasis was evidenced by enhanced tumorigenic phenotype of p15/p16-deleted PDAC cells when exposed to hepatocytes conditioned media. The liver is characterized by high-ammonia low-glutamine environment and transcriptomic assays indicated unique adaptation of PDAC cells to these conditions, including regulation of genes leading to reduced glutaminolysis, like overexpression of GLUL and reduction in GLS2. Furthermore, metabolic assays indicated an increase in glutamate derived from [U-13C]-glucose in p15/p16-deleted cells. Importantly, these cells thrived under high ammonia condition. These data suggest a unique role for genomic alterations in mediating tropism of PDAC. Among these alterations, p15/16 deletion was identified as a promoter of liver metastases. Further studies indicated a unique role for p15/16 in regulating glutaminolysis. These findings reveal vulnerabilities in PDAC cells, which may pave the way for the development of novel therapeutic strategies aiming at the prevention of liver metastases formation.

A Transgenic Model Reveals the Role of Klotho in Pancreatic Cancer Development and Paves the Way for New Klotho-Based Therapy

Simple Summary

We aimed to study the role of the anti-aging protein klotho and its secreted isoform, sKL, in pancreatic cancer. Three in vivo models, including a novel genetic mouse model and bioinformatics analyses, indicated klotho as a tumor suppressor in pancreatic ductal adenocarcinoma, and unveiled a unique klotho DNA hypermethylation pattern in pancreatic tumors. These results possess significant prognostic value, and further suggest that sKL may serve as a therapeutic agent for pancreatic ductal adenocarcinoma.

Abstract

Klotho is an anti-aging transmembrane protein, which can be shed and can function as a hormone. Accumulating data indicate that klotho is a tumor suppressor in a wide array of malignancies, and designate the subdomain KL1 as the active region of the protein towards this activity. We aimed to study the role of klotho as a tumor suppressor in pancreatic ductal adenocarcinoma (PDAC). Bioinformatics analyses of The Cancer Genome Atlas (TCGA) datasets revealed a correlation between the survival of PDAC patients, levels of klotho expression, and DNA methylation, and demonstrated a unique hypermethylation pattern of klotho in pancreatic tumors. The in vivo effects of klotho and KL1 were examined using three mouse models. Employing a novel genetic model, combining pancreatic klotho knockdown with a mutation in Kras, the lack of klotho contributed to PDAC generation and decreased mousece survival. In a xenograft model, administration of viral particles carrying sKL, a spliced klotho isoform containing the KL1 domain, inhibited pancreatic tumors. Lastly, treatment with soluble sKL prolonged survival of Pdx1-Cre; Kras^G12D/+;Trp53^R172H/+ (KPC) mice, a model known to recapitulate human PDAC. In conclusion, this study provides evidence that klotho is a tumor suppressor in PDAC. Furthermore, these data suggest that the levels of klotho expression and DNA methylation could have prognostic value in PDAC patients, and that administration of exogenous sKL may serve as a novel therapeutic strategy to treat PDAC.

BSCI-03. Adaptation of colorectal cancer cells to the brain microenvironment: The role of IRS2

Colorectal cancer (CRC) reflects the fourth most frequent etiology of brain metastasis (BM). Yet, molecular mechanisms supporting it are unknown. We aimed to explore drivers enabling adaptation of CRC cells to the brain and decipher mechanisms facilitating the process.

We analyzed the FoundationOne database, which contains genomic alterations data of cancer-related genes in over 16,000 human CRC primary and metastasis samples. Increased prevalence of IRS2 gene amplification was observed in 13% of BM, compared to only 3% of primary tumors or other metastatic sites. IRS2 is a cytoplasmic adaptor mediating effects of insulin and IGF-1 receptors and is involved in more aggressive behavior of different cancer types. In agreement with the genomic data, immunohistochemistry of human clinical samples showed increased expression of IRS2 protein in BM. We constructed an in-vitro system mimicking the brain microenvironment using cultured human astrocytes or their conditioned media. Under these conditions, IRS2-overexpressed CRC cells survived better and formed larger 3D spheres. IRS2-silenced CRC cells showed a mirror image. Moreover, in an intracranial CRC BM mouse model, IRS2-overexpressed cells generated larger brain lesions, while silencing IRS2 dramatically decreased tumor outgrowth and extended survival. Interestingly, transcriptomic analysis revealed enrichment of oxidative phosphorylation (OXPHOS) and Wnt/β-catenin pathways by IRS2. Indeed, IRS2-expressing cells showed increased mitochondrial activity and glycolysis-independent viability. Furthermore, IRS2-expressing cells had increased β-catenin transcriptional activity. Interestingly, β-catenin or IRS2 inhibition (using NT219) in IRS2-expressing cells decreased their viability, β-catenin transcriptional activity, and OXPHOS gene expression, suggesting involvement of IRS2 in modulating OXPHOS through β-catenin. β-catenin is known to confer 5-FU resistance; consequently, we showed that combination of 5-FU and NT219 worked in synergy, inhibited the formation of BM, and extended animal survival.

These data reveal the unique genomic profile of CRC BM and suggest IRS2 inhibition as a novel target for treatment of these patients.

Abstract 2854: Adaptation of colorectal cancer cells to the brain microenvironment: the role of IRS2

Colorectal cancer (CRC) reflects the fourth most frequent etiology of brain metastasis (BM), with rising incidence. Yet, molecular mechanisms supporting the formation of these lesions from CRC are unknown. We aimed to explore drivers enabling tropism and adaptation of CRC cells to the brain environment and decipher mechanisms facilitating the process. We analyzed the FoundationOne database, which contains genomic alterations data of cancer-related genes in over 16,000 human CRC primary and metastasis samples. Increased prevalence of insulin receptor substrate 2 (IRS2) gene amplification was noted in BMs relative to primary tumors and other metastatic sites. IRS2 is a cytoplasmic adaptor mediating effects of insulin and IGF-1 receptors and is known to be involved in more aggressive behavior of different cancer types. In agreement with the genomic data, immunohistochemistry of human clinical samples showed increased expression of IRS2 protein in BMs. We subsequently constructed an in vitro system mimicking the brain microenvironment using cultured human astrocytes or their conditioned media (CM). Under these conditions using InSphero system, IRS2-overexpressed CRC cells survived better and formed larger 3D spheres. IRS2-silenced CRC cells showed a mirror image. Moreover, in an intracranial CRC surgical implantation BMs mouse model, IRS2-overexpressed CRC cells generated larger brain lesions, while silencing IRS2 in IRS2-amplified CRC cells dramatically decreased tumor outgrowth and survival. Interestingly, transcriptomic analysis revealed significant enrichment of the oxidative phosphorylation pathway by IRS2. Indeed, IRS2-expressing CRC cells showed increased mitochondrial activity using Seahorse extracellular flux analysis and glycolysis-independent viability. Furthermore, IRS2-expressing cells showed enhanced AKT phosphorylation and inhibition of PI3K or AKT using Alpelisib or iAKT, respectively, slightly decreased their proliferation in CM, suggesting that mechanisms additional to the AKT pathway may mediate IRS2 activity. The Wnt/β-catenin pathway was among the most significantly enriched pathways in the transcriptome. Indeed, IRS2-expressing cells had increased transcriptional activity of the β-catenin. In addition, iAKT or Alpelisib, and most significantly the IRS2 inhibitor (NT219), decreased the transcriptional activity of β-catenin in IRS2-expressing CRC cells, suggesting relevance of IRS2 in activating β-catenin. Moreover, NT219 demonstrated significant and dose-dependent inhibition of CRC cells viability. These data reveal, for the first time, the unique genomic profile of CRC BMs and imply the IRS2 role in promoting CRC BMs. These effects may be mediated, at least in part, by modulation of the AKT and β-catenin pathway. Given the molecular signature described, the approach to patients with BMs may be significantly impacted by agents such as NT219.

Citation Format: Inbal Greenberg, Anat Klein, Rachel Grossman, Ethan Sokol, Eilam Yeini, Paula Ofek, Ronit Satchi-Fainaro, Bertrand Liang, Hadas Reuveni, Tami Rubinek, Ido Wolf. Adaptation of colorectal cancer cells to the brain microenvironment: the role of IRS2 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2854.

Abstract PO-003: Adaptation of colorectal cancer cells to the brain microenvironment: The role of IRS2

Brain metastases (BMs) from colorectal cancer (CRC) are currently the fourths leading cause of BMs, and their incidence is on the rise. Yet, mechanisms mediating the formation of BMs from CRC are unknown. We aimed to explore genomic drivers enabling tropism and adaptation of CRC cells to the brain environment and decipher mechanisms facilitating the process. We analyzed FoundationOne database, which contains genomic alterations data of cancer-related genes in over 16,000 human CRC primary and metastasis samples. Increased prevalence was noted in the insulin receptor substrate 2 (IRS2) gene, which was significantly amplified in BMs relative to primary tumors and other metastatic sites. IRS2 is a cytoplasmic adaptor mediating effects of insulin and IGF-1 receptors and is known to be involved in more aggressive behavior of different cancer types. In agreement with the genomic data, immunohistochemistry of human clinical samples showed increased expression of IRS2 protein in BMs. Next, we created an in-vitro system mimicking the brain microenvironment using human astrocytes or their conditioned media (CM). Under these conditions, IRS2-overexpressed CRC cells survived better and formed larger 3D spheres. IRS2-silenced CRC cells showed a mirror image. Furthermore, IRS2-overexpressed CRC cells generated larger brain lesions in an intracranial CRC BMs mice model. Interestingly, a transcriptomic analysis revealed significant enrichment of the AKT and β-catenin pathways by IRS2. Indeed, IRS2-amplified cells showed enhanced AKT phosphorylation and inhibition of PI3K or AKT using Alpelisib or Akt1/2 kinase inhibitor, respectively, effectively decreased their proliferation in CM. Importantly, IRS2-amplified cells had increased expression and transcriptional activity of the β-catenin, and AKT pathway inhibitors or IRS2 inhibitor (NT-219) had a more pronounced effect on the activity of β-catenin on those cells. These data indicate, for the first time, the unique genomic profile of CRC BMs and imply the IRS2 role in promoting CRC BMs. These effects may be mediated, at least in part, by modulation of the AKT and β-catenin pathway. These findings may pave the way for the development of novel therapeutic strategies to prevent BMs formation.

Citation Format: Inbal Greenberg, Anat Klein, Rachel Grossman, Ethan Sokol, Eilam Yeini, Paula Ofek, Ronit Satchi-Fainaro, Hadas Reuveni, Tami Rubinek, Ido Wolf. Adaptation of colorectal cancer cells to the brain microenvironment: The role of IRS2 [abstract]. In: Abstracts: AACR Special Virtual Conference on Epigenetics and Metabolism; October 15-16, 2020; 2020 Oct 15-16. Philadelphia (PA): AACR; Cancer Res 2020;80(23 Suppl):Abstract nr PO-003.

The Hormone KL1: A Regulator of Breast Cancer Cell Metabolism

BACKGROUND

Klotho is a transmembrane protein that can be shed and can act as a circulating hormone in three forms: soluble klotho (KL1 + KL2), KL1, and KL2. Klotho was discovered as a gene implicated in aging through inhibition of the IGF-I pathway. Our laboratory discovered the role of klotho as a tumor suppressor in breast cancer and other malignancies. Furthermore, we showed that the KL1 domain mediates this activity. Altered cancer cell metabolism is a hallmark of cancer and our lab demonstrated various effects of klotho on breast cancer cell metabolism. Thus, klotho inhibited glycolysis and activated adenosine monophosphate activating kinase (AMPK), an energy sensor pathway. Moreover, inhibition of AMPK reduced the tumor suppressor activity of klotho.

OBJECTIVES

To assess the effect of KL1 on breast tumor cells metabolism, as KL1 possesses the tumor suppressor activity of klotho.

METHODS

We used MCF-7 breast cancer cells treated with soluble or over-expressed KL1 and klotho. Glycolysis was assessed by measuring mRNA levels of key glycolytic enzymes using reverse transcription polymerase chain reaction and by measuring lactate and glucose levels in media. The AMPK pathway was studied by monitoring AMPK phosphorylation as well as its down-stream target, acetyl-CoA carboxylase, using western blotting. Wound healing assay was used to assess cell migration.

RESULTS

KL1 treatment reduced glycolytic enzymes mRNA levels and the activity of hexokinase, similar to klotho treatment. Furthermore, KL1 reduced glucose uptake and decreased lactate production. KL1 elevated phosphorylated acetyl-CoA carboxylase and phosphorylated AMPK levels. Inhibition AMPK (using a mutant AMPK activator) stopped KL1 from inhibiting cell migration, suggesting AMPK underlies klotho's tumor suppressor activity.

CONCLUSIONS

Our data indicate KL1 as a regulator of metabolic activity in breast cancer and suggest that metabolic alterations underlie KL1 tumor suppressor activities. Furthermore, as KL1 and klotho share a similar effect on cell metabolism, our results further support the central role KL1 domain plays in klotho's tumor suppressor activity.

Effect of ligand binding domain activating mutations of ESR1 on cellular metabolism, liver tropism, and chemotherapy resistance

e14506

Background: Mutations in the ligand binding domain (LBD) of estrogen receptor α (ER) confer constitutive transcriptional activity and resistance to endocrine therapies in breast cancer patients. Accumulating clinical data suggest adverse outcome for patients harboring tumors expressing these mutations. We aimed to elucidate mechanisms conferring this aggressive phenotype. Methods: Cells constitutively expressing physiologic levels of ER harboring activating LBD mutations were generated and characterized for viability, invasiveness and tumor formation in vivo. Gene expression profile was studied using RNAseq. Metabolic properties were assessed using global metabolite screen and direct measurement of metabolic activity. Response to chemotherapies was assessed using viability assays. Results: Cells expressing mutated ER showed increased proliferation, migration and in vivo tumorogenicity compared to cells expressing the WT-ER, even in the presence of estrogen. Experiments in mice revealed a more aggressive phenotype of the Y537S mutant compared to D538G as well as unique tissue predilection. Thus, 538G-ER cells exhibited liver tropism while Y537-ER cells mainly metastasized to the lungs and lymph nodes. Importantly, both mutations conferred resistance to paclitaxel and doxorubicin. Further studies indicated association of the mutated ER with upregulation of genes involved in tumor cell metabolism. Indeed, a global metabolic screen revealed distinct metabolic profile for cells harboring activating mutations, including the ability to utilize glutamine as an alternative carbon source. Moreover, we observed unique metabolic activities enabling cells to thrive in urea-reach environment of the liver, and overcome doxorubicin-induced stress responses. Conclusions: Taken together, these data indicate estrogen-independent rewiring of breast cancer cell metabolism by LBD-activating mutations, enabling aggressivene clinical behavior and chemotherapy resistance. Importantly, These unique metabolic activities may serve as a potential vulnerability and aid in the development of novel treatment strategies to overcome endocrine resistance.

The Longevity Hormone Klotho is a New Player in the Interacion of the Growth Hormone/Insulin-Like Growth Factor 1 Axis

Klotho was first discovered as an aging-suppressor gene. Mice that do not express klotho die prematurely with multiple symptoms of aging, several of which are also characteristic of decreased GH/IGF-1 axis activity. Klotho is highly expressed in the brain, the kidney, and parathyroid and pituitary glands, but can also serve as a circulating hormone by its shedding, forming soluble klotho (sKlotho) that can be detected in blood, cerebrospinal fluid and urine. Several lines of evidence suggest an association between klotho levels and activity of the GH/IHG-1 axis: The GH-secreting cells in the anterior pituitary of klotho-deficient mice are hypotrophic; klotho levels are altered in subjects with pathologies of the GH/IGF-1 axis; and accumulating data indicate that klotho is a direct regulator of GH secretion. Thus, klotho seems to be a new player in the intricate regulation of the GH/IGF-1 axis.

Abstract 4507: Upregulation of unfolded protein response (UPR): A novel activity of the tumor suppressor klotho in colorectal cancer

Klotho is a transmembrane protein, which can be shed and act as a circulating hormone. Klotho-deficient mice manifest a syndrome resembling accelerated aging, while klotho overexpression extends life span. We previously identified klotho as a breast and pancreatic tumor suppressor and as an inhibitor of the IGF-1 pathway. Recent data indicate klotho as a tumor suppressor in an array of malignancies, including colorectal cancer (CRC). We aimed to decipher the role of klotho as a tumor suppressor in CRC. Analysis of a public database (Oncomine) indicated reduced expression of klotho in CRC. Two models were employed to study the effect of klotho in vivo. Using the azoxymethane inflammation model, we discovered that klotho inhibited colon polyp formation. Using an orthotopic model consisting of direct injection of MC38 cells to the mice colons, we found that klotho inhibited colonic obstruction and tumor formation. Similarly, klotho inhibited colony formation and proliferation of CRC cell lines. Aberrant activation of the canonical Wnt pathway is implicated in CRC development and progression. β-catenin, the key effector of this pathway, functions with T-cell factor/lymphoid-enhancer-factor (TCF/LEF) to activate expression of Wnt target genes. While we did not see an effect of klotho on the IGF-1 pathway, it reduced Wnt3A and β-catenin levels as measured by Western blotting, and inhibited TFC/LEF transcriptional activation in luciferase assay. As transcriptional inhibition was abrogated by a constitutively active β-catenin, we suspected that klotho inhibited the pathway upstream of β-catenin. Indeed, co-immunoprecipitation analyses indicated direct interaction between klotho and Wnt3A. Yet, the inhibitory effect of klotho on CRC cell colony formation was only partially rescued by a constitutively active β-catenin. These data indicate on additional mechanisms involved in the TS activity of klotho. Thus, we conducted an RNA expression array and observed involvement of klotho in endoplasmic reticulum (ER) stress and unfolded protein response (UPR). Further studies showed that klotho induced elevation in XBP1 RNA levels, GRP78 protein levels, and eIF2α phosphorylation, all indicative of UPR regulation. Importantly, pharmacologic inhibition of ER stress and UPR overcame the growth suppression effect of klotho in CRC cells. Our data indicate klotho as a potent tumor suppressor in CRC, and suggest its role at very early stages of tumor formation, already at polyp formation. Our data also indicate, for the first time, klotho as a regulator of ER stress and UPR in cancer. These findings may pave the way for the development of novel therapeutic strategies based on enhancement of UPR.

Citation Format: Tal Etan, Tammi Rubinstein, Tami Rubinek, Shiri Shahmoon, Chen Varol, Ehud Zigmond, Rina Rosin-Arbesfeld, Iris Barshack, Ido Wolf. Upregulation of unfolded protein response (UPR): A novel activity of the tumor suppressor klotho in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4507. doi:10.1158/1538-7445.AM2017-4507

Abstract 5417: The tumor suppressor klotho: A master regulator of metabolism in breast cancer

One of the hallmarks of cancer is reprogramming of energy metabolism, characterized by a shift to aerobic glycolysis (Warburg effect). A major regulator of this phenomenon is the IGF-1/Pi3K/AKT pathway. Klotho is a transmembrane protein, which can be cleaved, shed and act as a circulating hormone. Klotho-deficient mice manifest a syndrome resembling accelerated aging, while klotho overexpression extends life span. Klotho is a potent tumor suppressor in BC. As klotho is a potent inhibitor of the IGF-1/Pi3K/AKT pathway in BC, we hypothesized that it may revert the metabolic switch in BC cells. We first analyzed the effect of klotho on the energy sensor enzyme AMP-activated kinase (AMPK) and its down-stream effector acetyl CoA carboxylase (ACC). Overexpression of klotho, or treatment with the soluble protein, elevated AMPK and ACC phosphorylation in three BC cell lines. AMPK is activated by the tumor suppressor liver kinase B1 (LKB1) and elevated AMP/ATP ratio. Expression of a dominant negative LKB1 prevented activation of AMPK by klotho and decreased the ability of klotho to inhibit cell growth and migration, implying that klotho tumor suppressor activities are LKB1 dependent. We next analyzed the effects of klotho on critical components of glucose metabolism. Treatment with soluble klotho reduced expression of the glucose transporter GLUT1 and the key glycolytic enzymes hexokinase2 (HK2), phosphofructokinase1 (PFK1), pyruvate kinase M2 (PKM2) and pyruvate dehydrogenase kinase 1(PDK1). Using the Seahorse analyzer we noted reduced oxidative mitochondrial metabolism and glycolysis following klotho treatment. Energy is obtained essentially in the mitochondria with the transfer of protons across the inner membrane that produces ATP. We, therefore, analyzed klotho effect on the mitochondria membrane potential and noted reduction in the mitochondria potential following treatment with klotho. Finally, we examined the effects of klotho on specific metabolites and also conducted an NMR-based metabolic profiling. In accordance with the alterations in signaling pathways and levels of glycolytic enzymes, klotho reduced glucose uptake and inhibited lactate, pyruvate and 3-hydroxy-butyrate production. Furthermore, klotho also inhibited ATP production. Taken together, our data indicate klotho as a regulator of metabolic activity in BC and suggest that reversal of the metabolic switch is a key mechanism of klotho-mediated tumor suppressor activities.

Citation Format: Tami Rubinek, Ido Wolf. The tumor suppressor klotho: A master regulator of metabolism in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5417. doi:10.1158/1538-7445.AM2017-5417

Klotho response to treatment with growth hormone and the role of IGF-I as a mediator

CONTEXT

Klotho is an aging-modulating protein expressed mainly in the kidneys, which can be cleaved and shed to act as a circulating hormone. Several lines of evidence suggest a tight interaction between klotho and the GH-IGF-I axis. We showed previously that klotho levels are decreased in pediatric patients with growth hormone deficiency (GHD). Our aim now is to investigate the effect of GH therapy on klotho levels in these patients and to elucidate the role of IGF-1 in mediating secretion of klotho.

BASIC PROCEDURES

Klotho levels were measured in 29 GHD pediatric patients (males=15, aged 12.2±3.3years), treated with GH for 2.5±2.8years; nineteen patients had samples obtained both before and during treatment. The effect of IGF-I and its downstream effectors on secretion of klotho to media was studied in COS-7 cells overexpressing klotho.

MAIN FINDINGS

Klotho levels increased under GH treatment (from 1321±691pg/ml to 3380±2120pg/ml, p<0.001), and were higher compared to controls (1645±778pg/ml, p<0.001), resulting in supraphysiological levels. Fold-increase in klotho correlated with fold-increase in IGF-I (r=0.63, p=0.004). Studies in COS-7 cells overexpressing klotho revealed mTOR-dependent induction of klotho shedding by IGF-I.

PRINCIPAL CONCLUSIONS

Klotho levels increased during GH treatment of pediatric GHD patients. This increase was associated with an increase in IGF-I levels. Furthermore, we showed, for the first time, a direct role of IGF-I in the regulation of klotho's shedding which depends on activation of the AKT-mTOR pathway. Our findings add further support for the close association between klotho and the GH/IGF-I axis.

Abstract 3679: Klotho suppresses colon cancer through modulation of the Wnt pathway and unfolded protein response

Aberrant activation of the canonical Wnt pathway is implicated in colorectal cancer (CC) development and progression. β-catenin, the key effector of this pathway, functions with T-cell factor/lymphoid-enhancer-factor (TCF/LEF) to activate expression of Wnt target genes. Klotho is a transmembrane protein, which can be shed and act as a circulating hormone. Klotho-deficient mice manifest a syndrome resembling accelerated aging, while klotho overexpression extends life span. We previously identified klotho as a breast and pancreatic tumor suppressor (TS). Recent data indicate klotho as a TS in an array of malignancies, including CC. Among other activities, klotho inhibits the insulin-like growth factor (IGF)-1 and Wnt pathways. We aimed to decipher the role of klotho as a TS in CC.

We first noted that klotho overexpression inhibited CC cell colony formation. Next, we examined in vivo effects using the azoxymethane mouse model, and found that klotho inhibited colon polyp formation. We then used an orthotopic model by injecting MC38 cells to mice colons, and found that klotho inhibited colonic obstruction and tumor formation.

While we did not see an effect of klotho on the IGF-1 pathway, klotho did affect the Wnt pathway. Klotho reduced Wnt3A and β-catenin levels as measured by Western blotting, and inhibited TFC/LEF transcriptional activation in luciferase assay. As transcriptional inhibition was abrogated by a constitutively active β-catenin, we suspected that klotho inhibited the pathway upstream of β-catenin. Indeed, co-immunoprecipitation analyses indicated direct interaction between klotho and Wnt3A. As the inhibitory effect of klotho on CC cell colony formation was only partially rescued by a constitutively active β-catenin, additional mechanisms may be involved. Thus, we conducted a cDNA expression microarray and involvement of klotho in endoplasmic reticulum (ER) stress and unfolded protein response (UPR) was observed. Further studies showed that klotho induced elevation in XBP1 RNA, GRP78 protein levels, and eIF2α phosphorylation, all indicative of a role klotho plays in UPR regulation.

Our data indicate klotho as a potent TS in CC, and suggest its role at early stages of tumor formation. The Wnt pathway partially mediates klotho effects in CC, however additional mechanisms, including ER stress response regulation, are involved.

Citation Format: Tami Rubinek, Tammi Rubinstein, Shiri Shahmoon, Chen Varol, Ehud Zigmond, Rina Rosin-Absesfelf, Iris Barshack, Ido Wolf. Klotho suppresses colon cancer through modulation of the Wnt pathway and unfolded protein response. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3679.

Abstract 3482: Inhibition of glucose metabolism in neuroendocrine tumors by lanreotide, sunitinib, and rapamycin

Background: Neuroendocrine tumors (NETs) represent a heterogeneous family of neoplasms, which may develop from different endocrine glands or endocrine cells dispersed throughout the digestive and respiratory tracts. Lanreotide is a somatostatin analog approved for the treatment of NETs. While Lanreotide extends survival of patients and slows tumor growth, controversy exists regarding its mechanism of action. We hypothesized that lanreotide can interfere with the metabolic activity of NETs, and compared its effect to that of rapamycin and sunitinib.

Methods: The pancreatic carcinoid BON-1 cells and pulmonary carcinoid NCI-H727 cells were used. Viability was tested using colony formation assay. mRNA levels of the glycolytic enzymes hexokinase 2 (HK2), lactate dehydrogenase (LDH) and pyruvate kinase M2 (PKM2) was tested using real-time PCR. Phosphorylation levels of AMP-activated kinase (AMPK) and acetyl CoA carboxylase (ACC) were tested using Western blot. The activity of HK2 was tested using HK enzymatic assay. Lactate secretion was tested in the routine biochemistry laboratory of our institution.

Results: Lanreotide, rapamycin and sunitinib significantly decreased colony formation. They also reduced relative expression levels of HK2, LDH and PKM2 24 and 48h after treatment and decreased HK2 activity after 24h. An increase in the phosphorylation levels of AMPK and ACC was observed shortly after treating the cells with lanreotide and rapamycin. All three agents also decreased lactate concentration in the media.

Conclusions: These data indicate tumor metabolism as an attractive target for therapies against NET, and a novel mechanism of action of somatostatin analogs, namely, alteration of tumor metabolism.

Citation Format: Tami Rubinek, Ayelet Shabtay-Orbach, Arkadi Hesin, Tammi Rubinstein, Ido Wolf. Inhibition of glucose metabolism in neuroendocrine tumors by lanreotide, sunitinib, and rapamycin. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3482.

The Role of Alpha-Klotho as a Universal Tumor Suppressor

The klotho gene is implicated in many physiological activities, among them aging, glucose metabolism, and phosphate and calcium metabolism. Many cellular activities of klotho were implicated in promoting these activities. Two of them, inhibition of the insulin-like growth factor-1 pathway and of the Wnt signaling pathway, are also major pathways associated with cancer development and progression. These discoveries prompted a surge of research aiming to elucidate the role of klotho in cancer. Studies show that klotho is universally silenced in a wide array of malignancies, including breast, pancreatic, ovarian, lung, colorectal, and melanoma, and that klotho's expression can serve as an invaluable prognostic marker. Epigenetic mechanisms, ie, promoter hypermethylation and histone deacetylation, are mainly associated with klotho's silencing; however, different micro-RNAs were also demonstrated to be involved in the process. The activity of klotho on cancer cells growth was also widely investigated, and accumulating data suggest that klotho forced expression or treatment with the soluble protein can inhibit cancer development and progression. Moreover, studies now aim to reveal the specific region in klotho protein that underlies this anticancer activity in order to develop efficient and safe klotho-based medications.

Klotho and the Growth Hormone/Insulin-Like Growth Factor 1 Axis: Novel Insights into Complex Interactions

The growth hormone (GH)/insulin-like growth factor (IGF)-1 axis is pivotal for many metabolic functions, including proper development and growth of bones, skeletal muscles, and adipose tissue. Defects in the axis' activity during childhood result in growth abnormalities, while increased secretion of GH from the pituitary results in acromegaly. In order to keep narrow physiologic concentration, GH and IGF-1 secretion and activity are tightly regulated by hypothalamic, pituitary, endocrine, paracrine, and autocrine factors. Klotho was first discovered as an aging-suppressor gene. Mice that do not express klotho die prematurely with multiple symptoms of aging, several of them are also characteristic of decreased GH/IGF-1 axis activity. Klotho is highly expressed in the brain, the kidney, and parathyroid and pituitary glands, but can also serve as a circulating hormone by its shedding, forming soluble klotho that can be detected in blood, cerebrospinal fluid, and urine. Several lines of evidence suggest an association between klotho levels and activity of the GH/IGF-1 axis: the GH-secreting cells in the anterior pituitary of klotho-deficient mice are hypotrophic; klotho levels are altered in subjects with pathologies of the GH/IGF-1 axis; and accumulating data indicate that klotho is a direct regulator of GH secretion. Thus, klotho seems to be a new player in the intricate regulation of the GH/IGF-1 axis.

The Effect of Klotho Treatment on Atherogenesis, Blood Pressure, and Metabolic Parameters in Experimental Rodent Models

Klotho is a transmembrane protein, expressed mainly in the kidneys and the choroid plexus. The extracellular domain of klotho is composed of 2 internal repeats, KL1 and KL2, which can be cleaved and act as hormones. Klotho-deficient mice develop a phenotype resembling human aging. Laboratory and clinical data suggest a favorable effect of klotho on atherosclerosis, high blood pressure, and metabolic syndrome. Therefore, we aimed to study the effect of klotho treatment on atherogenesis, blood pressure, and metabolic parameters in experimental rodent models. Fructose-fed Sprague-Dawley rats (metabolic syndrome model) and apolipoprotein E (apoE -/-) knock-out mice (atherosclerosis model) were treated with either klotho or its active domain KL1. In apoE -/- mice, klotho unexpectedly elevated plasma cholesterol and triglyceride levels compared to the control group. Yet, it did not increase the aortic sinus atherosclerotic lesion area. In fructose-fed Sprague-Dawley rats, klotho treatment did not lower blood pressure or plasma triglyceride levels. Although KL1 treatment did not lower blood pressure or plasma insulin levels, it significantly reduced the elevation of total plasma triglyceride levels (from 2.3-fold to 1.6-fold, p<0.05) due to lower triglyceride-rich VLDL levels. Klotho did not show any beneficial effects on atherosclerosis and components of the metabolic syndrome and was associated with increased plasma cholesterol levels. On the other hand, treatment with KL1 may lower plasma triglyceride levels independent of insulin. Additional studies are required in order to decipher the complex role of klotho and its active domains in the regulation of plasma lipid levels.

Abstract 1184: The tumor suppressor klotho: a master regulator of metabolism in breast cancer

One of the hallmarks of cancer is reprogramming of energy metabolism, characterized by a shift to aerobic glycolysis (Warburg effect). This metabolic switch provides cancer cells appropriate conditions required for enhanced proliferation and survival. A major regulator of this phenomenon is the IGF-1/Pi3K/AKT pathway. Klotho is a transmembrane protein, which can be cleaved, shed and act as a circulating hormone. Klotho-deficient mice manifest a syndrome resembling accelerated aging, while klotho overexpression extends life span. We identified klotho as a tumor suppressor in breast and pancreatic cancers and recent data indicate it as a potent tumor suppressor in a wide array of malignancies. As klotho is a potent inhibitor of the IGF-1/Pi3K/AKT pathway in breast cancer, we hypothesized it may revert the metabolic switch in cancer cells.

A master regulator of energy metabolism is the energy sensor enzyme, AMP-activated kinase (AMPK). We first analyzed the effect of klotho on AMPK and its down-stream effector acetyl CoA carboxylase (ACC) in MCF-7, T47D and MDA-MB-231 breast cancer cell lines. These cell lines represent different disease phenotypes. Overexpression of klotho, or treatment with the soluble protein, AMPK and ACC phosphorylation in all three cell lines. AMPK is activated by the tumor suppressor liver kinase B1 (LKB1) and elevated AMP/ATP ratio or by calcium/calmodulin-dependent protein kinase kinase (CAMKK) 1β. LKB1 was expressed in all cell lines, although lower expression was noted in MD-MB-231 cells. Expression of a dominant negative LKB1 prevented activation of AMPK by klotho. Furthermore, it decreased the ability of klotho to inhibit cell growth and migration, implying that klotho tumor suppressor activity may be LKB1 dependent.

We next analyzed the effects of klotho on critical components of glucose metabolism. Treatment with soluble klotho reduced expression of the glucose transporter GLUT1 and the key glycolytic enzymes hexokinase2 (HK2), phosphofructokinase1 (PFK1), pyruvate kinase M2 (PKM2) and pyruvate dehydrogenase kinase 1(PDK1).

Finally, we examined the effects of klotho on specific metabolites and also conducted an NMR-based metabolic profiling. In accordance with the alterations in signaling pathways and levels of glycolytic enzymes, klotho reduced glucose uptake and inhibited lactate, pyruvate and 3-hydroxy-butyrate production. Furthermore, klotho also inhibited ATP production.

Taken together, our data indicate klotho, for the first time, as a regulator of metabolic activity in breast cancer and suggest that reversal of the metabolic switch is a key mechanism of klotho-mediated tumor suppressor activities.

Citation Format: Riva Shmulevich, Tammi Rubinstein, Taly Scherf, Ido Wolf, Tami Rubinek. The tumor suppressor klotho: a master regulator of metabolism in breast cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1184. doi:10.1158/1538-7445.AM2015-1184

Abstract 4959: Klotho suppresses colon cancer through modulation of the Wnt pathway and unfolded protein response

Aberrant activation of the canonical Wnt signal transduction pathway is implicated in the development and progression of colorectal cancer (CC). The key effector protein of this pathway is β-catenin, which functions with T-cell factor/lymphoid enhancer factor (TCF/LEF) to activate expression of Wnt target genes. Klotho is a transmembrane protein, which can be cleaved, shed and act as a circulating hormone. Klotho-deficient mice manifest a syndrome resembling accelerated aging, while klotho overexpression extends life span. We have previously identified klotho as a potent tumor suppressor in breast and pancreatic cancer, and recent data indicate it as a potent tumor suppressor in a wide array of malignancies, including CC. The activities of klotho include inhibition of the insulin like growth factor (IGF)-1 and the Wnt pathways. We aimed to decipher the role of klotho as a tumor suppressor and modulator of the Wnt pathway in CC.

We first tested the effect of klotho on proliferation of CC cells and noted that overexpression of klotho inhibited colony formation of the HCT 116, SW480, HT-29, Colo-320 and RKO CC cells. We next examined the effects of klotho in vivo, using the azoxymethane (AOM) model, and found that daily administration of klotho to mice inhibited formation of colon polyps induced by AOM. While we did not see an effect of klotho on the IGF-1 signaling pathway, klotho did affect the Wnt pathway. Klotho reduced Wnt3A and β-catenin protein levels as measured by Western blotting, and inhibited transcriptional activity of the Wnt pathway as evidenced in luciferase assay. Moreover, this transcriptional inhibition was abrogated by overexpression of a constitutively active β-catenin. We, therefore, suspected that klotho inhibited the pathway upstream of β-catenin. Indeed, co-immunoprecipitation analyses indicated direct interaction between klotho and Wnt3A.

As the inhibitory effect of klotho on colony formation of CC cells was only partially rescued by transfection with constitutively active β-catenin, we concluded that additional mechanisms may mediate the effects of klotho. In order to elucidate these mechanisms, we conducted a cDNA expression microarray and involvement of klotho in endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) was observed.

Taken together, our data indicate klotho as a potent tumor suppressor in CC and suggest its role already at the early stages of polyp formation. Klotho effects in CC are partially mediated by the Wnt pathway however additional mechanisms, including regulation of ER stress response, are involved.

Citation Format: Tammi Rubinstein, Shiri Shahmoon, Gil Har Zahav, Nir Skalka, Tal Etan, Rina Arbesfeld, Metsada Pasmanik-Chor, Tami Rubinek, Ido Wolf. Klotho suppresses colon cancer through modulation of the Wnt pathway and unfolded protein response. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4959. doi:10.1158/1538-7445.AM2015-4959

Klotho expression in cervical cancer: differential expression in adenocarcinoma and squamous cell carcinoma

AIMS

Klotho is a trans-membrane protein that serves as a tumour suppressor in a wide array of malignancies. Recent data suggest it as an epigenetically silenced tumour suppressor in cervical cancer. Yet, the expression pattern of klotho in cervical cancer has not been determined. We aimed to study the expression of klotho in squamous cell carcinomas (SQCC) and adenocarcinoma (ADC) of the cervix.

METHODS

Klotho expression was analysed by immunohistochemistry in 44 SQCC samples, 38 ADC samples and the adjacent normal tissue. For each sample, percentage of positive stained cells, staining intensity and a combined staining score were recorded. Staining was validated by measuring klotho mRNA levels, using quantitative RT-PCR, in 18 of the samples.

RESULTS

Klotho expression was high in all endocervical and exocervical normal tissues adjacent to tumour. No expression of klotho was noted in 7 out of 38 (18.4%) ADC samples and in 2 out of 44 (4.5%) SQCC samples. Staining intensity, number of positively stained cells and combined intensity score were all lower in tumours compared with normal adjacent tissues in ADC and SQCC. Klotho mRNA levels highly correlated with immunohistochemical (IHC) staining (p=0.008).

CONCLUSIONS

We found reduced klotho expression in cervical carcinoma, especially in ADC, compared with normal adjacent tissue. Our results support the role of klotho as a potential tumour suppressor in cervical cancer. Further studies are required in order to establish the therapeutic role of klotho in cervical carcinoma and identify patients who may benefit from it.

Alteration in serum klotho levels in anorexia nervosa patients

BACKGROUND & AIMS

Klotho is a trans-membrane protein which can be shed to act as a hormone; its blood levels may be regulated by the GH/IGF-1 axis. Klotho deficient mice exhibit short lifespan and characteristics of aging and malnutrition, including decreased fat and muscle mass, osteopenia, and impaired fertility. As anorexia nervosa (AN) is characterized by malnutrition and GH resistance, we hypothesized klotho levels would be altered in AN, and aimed to assess klotho levels in undernourished AN patients and changes in klotho following weight rehabilitation.

PARTICIPANTS AND METHODS

19 adolescent female AN inpatients (aged 16.1 ± 1.8 years) admitted to an inpatient service for eating disorders in a tertiary center were recruited. Blood samples were obtained on admission and after weight restoration (interval 4.0 ± 2.3 months) and analyzed for klotho, IGF-1, calcium, phosphorus, and alkaline phosphatase.

RESULTS

Klotho levels on admission were lower than expected for age, and correlated with lumbar spine BMD Z-score (r = -0.81, p < 0.001) and alkaline phosphatase levels (r = 0.66, p = 0.003) but not with age, height-SDS, weight-SDS, BMI-SDS, or serum calcium, phosphorus and IGF-1 levels. Both IGF-1 and klotho levels increased significantly during hospitalization (IGF-1: 44 ± 17 nmol/l to 53 ± 11 nmol/l, p = 0.008; klotho: 1061 ± 421 pg/ml to 1519 ± 781 pg/ml, p = 0.008).

CONCLUSIONS

Klotho levels are low in the acute stage of AN and increase with nutritional rehabilitation. Low klotho on admission may be secondary to low IGF-1 levels and may contribute to the clinical manifestations of AN. The role of klotho in the pathophysiology of AN and as a novel marker of disease severity should be further explored.

Reduced expression and growth inhibitory activity of the aging suppressor klotho in epithelial ovarian cancer

Klotho is an anti-aging transmembrane protein, which can be shed and function as a hormone. Accumulating data indicate klotho as a tumor suppressor in a wide array of malignancies, and we identified klotho as an inhibitor of the insulin-like growth factor (IGF-1) pathway in cancer cells. As this pathway is significant in the development of epithelial ovarian cancer (EOC) we studied klotho expression and activity in this tumor. Klotho mRNA levels were reduced in 16 of 19 EOC cell lines and immunohistochemistry analysis revealed high expression in normal ovaries, and reduced expression in 100 of 241 high grade papillary-serous adenocarcinoma of the ovaries, fallopian tubes and peritoneum. Reduced expression was associated with wild-type BRCA status. Klotho reduced EOC cell viability, enhanced cisplatin sensitivity, and reduced expression of mesenchymal markers. Finally, klotho inhibited IGF-1 pathway activation and inhibited transcriptional activity of the estrogen receptor. In conclusion, klotho is silenced in a substantial subset of the tumors and restoring its expression slows growth of EOC cells and inhibits major signaling pathways. As klotho is a hormone, treatment with klotho may serve as a novel treatment for EOC.

Association between decreased klotho blood levels and organic growth hormone deficiency in children with growth impairment

Objective

Klotho is an aging-modulating protein expressed mainly in the kidneys and choroid plexus, which can also be shed, released into the circulation and act as a hormone. Klotho deficient mice are smaller compared to their wild-type counterparts and their somatotropes show marked atrophy and reduced number of secretory granules. Recent data also indicated an association between klotho levels and growth hormone (GH) levels in acromegaly. We aimed to study the association between klotho levels and GH deficiency (GHD) in children with growth impairment.

Design

Prospective study comprising 99 children and adolescents (aged 9.0±3.7 years, 49 male) undergoing GH stimulation tests for short stature (height-SDS = −2.1±0.6). Klotho serum levels were measured using an α-klotho ELISA kit.

Results

Klotho levels were significantly lower (p<0.001) among children with organic GHD (n = 11, 727±273 pg/ml) compared to both GH sufficient participants (n = 59, 1497±754 pg/ml) and those with idiopathic GHD (n = 29, 1645±778 pg/ml). The difference between GHS children and children with idiopathic GHD was not significant. Klotho levels positively correlated with IGF-1- standard deviation scores (SDS) (R = 0.45, p<0.001), but were not associated with gender, pubertal status, age or anthropometric measurements.

Conclusions

We have shown, for the first time, an association between low serum klotho levels and organic GHD. If validated by additional studies, serum klotho may serve as novel biomarker of organic GHD.

The aging suppressor klotho: a potential regulator of growth hormone secretion

Klotho is a transmembranal protein highly expressed in the kidneys, choroid plexus, and anterior pituitary. Klotho can also be cleaved and shed and acts as a circulating hormone. Klotho-deficient mice (kl/kl mice) develop a phenotype resembling early aging. Several lines of evidence suggest a role for klotho in the regulation of growth hormone (GH) secretion. The kl/kl mice are smaller compared with their wild-type counterparts, and their somatotropes show reduced numbers of secretory granules. Moreover, klotho is a potent inhibitor of the IGF-I pathway, a negative regulator of GH secretion. Therefore, we hypothesized that klotho may enhance GH secretion. The effect of klotho on GH secretion was examined in GH3 rat somatotrophs, cultured rat pituitaries, and cultured human GH-secreting adenomas. In all three models, klotho treatment increased GH secretion. Prolonged treatment of mice with intraperitoneal klotho injections increased mRNA levels of IGF-I and IGF-I-binding protein-3 mRNA in the liver, reflecting increased serum GH levels. In accord with its ability to inhibit the IGF-I pathway, klotho partially restored the inhibitory effect of IGF-I on GH secretion. Klotho is known to be a positive regulator of basic bFGF signaling. We studied rat pituitaries and human adenoma cultures and noted that bFGF increased GH secretion and stimulated ERK1/2 phosphorylation. Both effects were augmented following treatment with klotho. Taken together, our data indicate for the first time that klotho is a positive regulator of GH secretion and suggest the IGF-I and bFGF pathways as potential mediators of this effect.

Endocrine resistance in breast cancer: focus on the phosphatidylinositol 3-kinase/akt/mammalian target of rapamycin signaling pathway

Breast cancer is the most common cancer among women. Up to 75% of breast cancers express the estrogen receptor (ER)α and/or the progesterone receptor (PR). Patients with hormone receptor-positive metastatic breast cancer are typically treated with endocrine therapy. Yet, not all patients with metastatic breast cancer respond to endocrine treatments and are considered to have primary (de novo) resistance. Furthermore, all patients who initially respond to endocrine treatment will eventually develop acquired resistance. Several mechanisms have been linked to the development of endocrine resistance, including reduced expression of ERα, altered regulation of the ER pathway, and activation of various growth factor signaling pathways, among them the phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling pathway. This pathway is involved in critical processes including cell survival, proliferation, and angiogenesis, and plays a central role in breast cancer development. Recent laboratory and clinical data implicate this pathway as mediating endocrine resistance, and agents directed against critical components of this pathway are either already approved for clinical use in breast cancer patients or are currently being tested in clinical trials. In this review, we describe the interaction between the PI3K/Akt/mTOR pathway and the ER cascade, its role in mediating endocrine resistance, and the clinical implications of this interaction.

Association between variants of 5-hydroxytryptamine receptor 3C (HTR3C) and chemotherapy-induced symptoms in women receiving adjuvant treatment for breast cancer

Administration of chemotherapy is associated with a wide array of symptoms affecting quality of life. Genetic risk factors for severity of chemotherapy-induced symptoms have not been determined. The present study aimed to explore the associations between polymorphisms in candidate genes and chemotherapy-induced symptoms. Women treated with at least two cycles of adjuvant doxorubicin and cyclophosphamide, with or without paclitaxel for early breast cancer (n = 105) completed the memorial symptom assessment scale and provided blood for genotyping. DNA was extracted from peripheral blood leukocytes and assayed for single nucleotide polymorphisms (SNPs) in GTP cyclohydrolase 1 (GCH1, rs10483639, rs3783641, and rs8007267), catecholamine-o-methyltransferase (COMT, rs4818), and 5-hydroxytryptamine (serotonin) receptor 3C (HTR3C, rs6766410, and rs6807362). Genotyping of HTR3C revealed a significant association between the presence of rs6766410 and rs6807362 SNPs (K163 and G405 variants) and increased severity of symptoms (p = 0.0001 and p = 0.007, respectively). Multiple regressions revealed that rs6766410 and rs6807362, but not age or stage at diagnosis, predicted severity of symptoms (p = 0.001 and p = 0.006, respectively) and explained 12 % of the variance in each regression model. No association was found between the genetic variants of CGH1 or COMT and symptom score. Our study indicates, for the first time, an association between variants of HTR3C and severity of chemotherapy-induced symptoms. Analyzing these genetic variants may identify patients at increased risk for the development of chemotherapy-induced symptoms and targeting the serotonin pathway may serve as a novel treatment strategy for these patients.

D538G mutation in estrogen receptor-α: A novel mechanism for acquired endocrine resistance in breast cancer

Resistance to endocrine therapy occurs in virtually all patients with estrogen receptor α (ERα)-positive metastatic breast cancer, and is attributed to various mechanisms including loss of ERα expression, altered activity of coregulators, and cross-talk between the ERα and growth factor signaling pathways. To our knowledge, acquired mutations of the ERα have not been described as mediating endocrine resistance. Samples of 13 patients with metastatic breast cancer were analyzed for mutations in cancer-related genes. In five patients who developed resistance to hormonal therapy, a mutation of A to G at position 1,613 of ERα, resulting in a substitution of aspartic acid at position 538 to glycine (D538G), was identified in liver metastases. Importantly, the mutation was not detected in the primary tumors obtained prior to endocrine treatment. Structural modeling indicated that D538G substitution leads to a conformational change in the ligand-binding domain, which mimics the conformation of activated ligand-bound receptor and alters binding of tamoxifen. Indeed, experiments in breast cancer cells indicated constitutive, ligand-independent transcriptional activity of the D538G receptor, and overexpression of it enhanced proliferation and conferred resistance to tamoxifen. These data indicate a novel mechanism of acquired endocrine resistance in breast cancer. Further studies are needed to assess the frequency of D538G-ERα among patients with breast cancer and explore ways to inhibit its activity and restore endocrine sensitivity.

A genetic variant of 5-hydroxytryptamine receptor 3C (HTR3C): A novel link to chemotherapy-induced side effects

9630

Background: Symptom clusters are defined as three or more concurrent symptoms that are related to each other. Clusters may stem from common physiological mechanisms and may better represent adverse effects to chemotherapy compared to individual symptoms. We aimed to identify association between the experience of symptom clusters and specific genetic alterations. Methods: Study population consisted of 108 breast cancer patients who received over two cycles of adjuvant doxorubicin and cyclophosphamide (AC) treatment at the oncology institute of the Sheba Medical Center. Participants completed the Memorial Symptom Assessment Scale, the Lee Fatigue Scale and the Center for Epidemiological Studies Depression Scale. Hierarchical cluster analysis was used to identify patients' subgroups based on their symptom experience. For the genetic analyses, DNA was extracted from peripheral blood and single nucleotide polymorphisms (SNPs) of candidate genes were tested using restriction endonuclease assays. Results: Two distinct subgroups were identified based on severity of fatigue, depression, nausea, and change in food tastes: "all high" (n=79) and "all low" (n=29) level of all symptoms. As patients did not have active cancer, symptoms were attributed solely to chemotherapy. A genetic variant of HTR3C (rs6766410) results in a substitution of asparagine to lysine (N163K) may be associated with nausea and vomiting. We tested the association between this variant and symptom score. 51 of 75 (68%) patients with high symptom score harbored the variant allele, compared to 13 of 28 (46%) of those with low symptom score (p=0.038). Conclusions: Analysis of genetic background of clusters, rather than for individual symptoms, represents a novel approach for the study of chemotherapy-induced side effects. This approach enabled the identification of HTR3C variant as a possible mediator of side effects following treatment with AC. Discovering the genetic basis of symptom clusters may lead to the development of novel diagnostic and therapeutic modalities able to improve symptom management. This may translate to improved outcome among chemotherapy-treated cancer patients.

D538G acquired mutation of estrogen receptor (ER) alpha: A novel mechanism of endocrine resistance in metastatic breast cancer

e11578

Background: Resistance to endocrine therapy occurs in virtually all patients with ER-positive metastatic breast cancer (MBC) and is attributed to various mechanisms including loss of ER expression, altered activity of coregulators and cross-talk between the ER and growth factor signaling pathways. To our knowledge, acquired mutations of the ER have not been described as mediating endocrine resistance to endocrine treatment. Methods: Deep sequencing of the ER was conducted, as part of a commercially available next-generation sequencing of 182 cancer-related genes, on samples obtained from 10 heavily pre-treated, endocrine resistant patients with ER positive MBC. In one patient, a sample obtained at diagnosis was also available. Mutated ER was cloned and overexpressed in breast cancer cells. Transcriptional activity was tested using estrogen response element (ERE)-Luciferase construct, effects on viability were tested using MTT assays and computerized modeling was used to assess structural effects. Results: A novel mutation resulting in substitution of aspartic acid at position 538 to glycine was identified in 4 of 10 samples. Moreover, in one case in which samples were available prior to and following development of resistance, the D538G mutation was noted only in the latter sample. Structural modeling indicated that the substitution leads to a conformational change in the ligand binding domain which prevents binding of either estrogen or tamoxifen and mimics the conformation of activated receptor. Experiments in cell lines indicated constitutive ligand-independent transcriptional activity of the mutated receptor. Overexpression of the receptor in MCF-7 cells enhanced proliferation and conferred resistance to treatment with tamoxifen and fulvestarnt. Conclusions: We report here a novel mutation D538G of the ER in human breast cancer and demonstrate its role in mediating resistance to endocrine treatment. Our study also indicates, for the first time, acquired mutation of the ER as a novel mechanism of endocrine resistance. Further studies on larger populations and on less selected patients are needed in order to assess the accurate frequency of this novel mutation.

Abstract 541: Klotho-induced dissociation between activation and nuclear localization of extracellular signal-regulated kinase (ERK) 1/2: A novel growth inhibitory mechanism in breast cancer cancer

Klotho is a transmembranal protein implicated in aging and in calcium and phosphate metabolism. Klotho-deficient mice manifest a syndrome resembling accelerated aging, whereas, klotho over expression in mice extends life span. Klotho can be cleaved, shed and act as a circulating hormone. We have recently identified klotho as a potent tumor suppressor in breast and pancreatic cancers. We found that klotho is epigenetically silenced in these cancers and treatment with klotho inhibits proliferation of cancer cells in vitro and in vivo. We also showed that klotho inhibits bFGF-induced ERK phosphorylation. The ERK cascade plays a major role in tumorigenesis. Upon activation of the ERK cascade, ERK1/2 are phosphorylated and translocate to the nucleus, where they phosphorylate numerous substrates.

Using visualization of endogenous and GFP-tagged ERK2 and cell fractionation studies, we discovered that klotho inhibits nuclear translocation of phosphorylated ERK1/2. Furthermore, upon either klotho transfection or treatment with soluble klotho we noted activation of cytoplasmatic targets, but not of nuclear targets of ERK2. Thus RSK, an ERK2 cytoplasmic target, is activated following klotho co-treatment with bFGF. On the other hand, the ERK2 nuclear target Elk exhibited reduced activity under these conditions. That was evidenced by decreased Elk phosphorylation, and a decline in the mRNA expression of Elk-regulated gene cFOS.

One of klotho activities is regulation of calcium homeostasis through activation of the calcium channels TRPV5/6, resulting in increased intra-cellular levels of calcium. Interestingly, increased calcium levels have been shown recently to prevent nuclear translocation of activated ERK2. We hypothesized that TRPV6 may mediate klotho effects toward ERK1/2. Indeed, using visualization of GFP-tagged TRPV6 we noted that klotho recruited TRPV6 to the cell membrane and using co-immunoprecipitation noted an interaction between klotho and TRPV6 in breast cancer cells. Furthermore, overexpression of TRPV6 inhibited colony formation of these cells and the effect was augmented by co-transfection with klotho. Elevation in calcium levels by TRPV6 is expected to affect genes involved in regulating cellular calcium levels. Therefore, we analyzed the effects of klotho on the calcium binding protein S100A6, and on stromal interaction molecule-1 (STIM-1) which activates the "store-operated" ORAI1 calcium ion channels in plasma membrane. We noted, for the first time, that klotho down-regulated these genes.Taken together, our data indicate novel activities of klotho in cancer cells: regulation of intracellular calcium trafficking and dissociation between activation and nuclear translocation of ERK1/2.

Citation Format: Shiri Shahmoon, Tami Rubinek, Ido Wolf. Klotho-induced dissociation between activation and nuclear localization of extracellular signal-regulated kinase (ERK) 1/2: A novel growth inhibitory mechanism in breast cancer cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 541. doi:10.1158/1538-7445.AM2013-541

Abstract 3557: The aging suppressor hormone Klotho inhibits ovarian cancer cell proliferation by down-regulation of the estrogen receptor

Klotho is a 1012 amino acid (aa) long transmembranal protein, which can be cleaved, shed and act as a circulating hormone. Klotho contains two regions named KL1 and KL2, each about 500aa long. Klotho deficient mice present a syndrome of early aging, while overexpression of klotho extends lifespan. Klotho is an essential co-factor for the activity of FGF23 and thus serves as a major regulator of phosphate homeostasis. Klotho is also a potent inhibitor of the insulin growth factor (IGF)-1 pathway. We have identified klotho as a tumor suppressor in breast and pancreatic cancer. Recently, klotho activity as a tumor suppressor was observed also in melanoma and in cervix, lung, colon and gastric cancers. As klotho is expressed in the normal ovary, we undertook to study the expression and activity of klotho in ovarian cancer.

We first analyzed klotho expression, using quantitative RT-PCR and Western blotting, in 18 ovarian cancer cell lines and noted high levels of klotho mRNA and protein in only three lines. We next used immunohistochemistry analysis to study klotho expression in a tissue array containing 277 primary and recurrent ovarian, fallopian and primary peritoneal cancers, along with 22 normal and benign tumor samples. While high klotho expression was noted in all normal samples, reduced expression was noted in 30% of the tumors. Reduced expression was not associated with histology, tumor location or stage. Overexpression of either full length klotho or KL1 reduced clonal growth of OvCa432, SKOV3 and ES2 ovarian cancer cell lines by 80%, 60%, and 0%, respectively.

Klotho inhibits the IGF-1 pathway in pancreatic and breast cancer cells. As the IGF-1 pathway plays an important role in ovarian cancer development, we studied the effect of klotho on this pathway in ovarian cancer cell lines. Klotho inhibited IGF-1-mediated AKT activation, and to a lesser degree ERK1/2 phosphorylation, in SKOV3 and OvCa432 cells. Interestingly, ES2 cells did not respond to IGF-1.

Estrogen receptor (ER)α and progesterone receptor (PR) have a significant role in ovarian cancer development. ERα is expressed in a majority of ovarian cancers, while PR is less abundant, and its expression is a marker for better prognosis. We found that klotho reduces ERα expression and activity in SKOV3 and OvCa432. Interestingly, klotho elevated PR-A isoform expression in these cell lines.

In conclusion, unlike in breast and pancreas cancer, where klotho was identified as a potent tumor suppressor in most cancer subtypes, and the IGF-1 pathway was inhibited in a wide array of cell lines, in the ovary, klotho plays a role in a smaller subset of tumors. The characteristics of this group have not been identified yet. However, it appears that ERα inhibition and PR-A up-regulation may play a role in mediating klotho activities in this subset.

Citation Format: Irina Lojkin, Omer Schwartzman, Tami Rubinek, Ido Wolf. The aging suppressor hormone Klotho inhibits ovarian cancer cell proliferation by down-regulation of the estrogen receptor. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3557. doi:10.1158/1538-7445.AM2013-3557

Abstract 5388: Altered regulation of metabolic pathways by the hormone glucagon-like peptide 1 in breast cancer induces growth inhibition

Ample data indicate an association between Type 2 diabetes mellitus (T2DM) and increased risk of breast cancer. The incretin hormone glucagon-like peptide-1 (GLP-1) is a 31-amino acids long peptide-hormone, secreted from intestinal L cells in response to food intake and, through activation of G-protein coupled receptor (GPCR) located on pancreatic β cells, serves as the major regulator of postprandial insulin secretion. In hepatocytes and adipocytes GLP-1 regulates metabolic pathways like glucose uptake and lipid biosynthesis. GLP-1 levels are reduced in T2DM, and long acting GLP-based medications are currently approved for treatment of T2DM.

We have recently discovered GLP-1 as a novel player in the complex interaction between T2DM and breast cancer. GLP-1 inhibited proliferation of breast cancer cells in vitro and in vivo, induced cAMP accumulation and inhibited AKT activation. Tumor cells acquire a metabolic switch essential for their survival, allowing cells to function under stress and produce precursors needed for the synthesis of macromolecules. This phenomenon is associated with activation of the AKT pathway and inhibition of AMP activated protein kinase (AMPK). Based on our observations and on known metabolic activities of GLP-1in other cell types, we hypothesized that it may reverse the metabolic switch in breast cancer cells, thus, leading to cell death.

AMPK inhibition, using compound C and siRNA, abolished GLP1-mediated MCF-7 and MDA-MB-231 cell death, implying this metabolic pathway as central to GLP-1 activity in breast cancer. Indeed, GLP1 induced AMPK phosphorylation in breast cancer cell lines. Accordingly, acetyl CoA carboxylase (ACC), an essential enzyme for fatty acid synthesis and a downstream target of AMPK, was phosphorylated by AMPK. Adenylate cyclase inhibitor 2′5′dideoxy adenosine prevented GLP-1-induced AMPK and ACC phosphorylation, suggesting cAMP as a regulator of this pathway. AMPK can be activated generally by LKB1 or CAMKK1β. As MDA-MB231 cells do not express LKB1 we suspected that GLP-1 utilizes CAMKK1β for AMPK activation in breast cancer cells. Indeed, we discovered that CAMKK1β inhibition abrogated AMPK activation by GLP-1. The mammalian target of rapamycin (mTOR) pathway is regulated by AMPK. We monitored pathway activity by measuring phosphorylation of S6-kinase and its substrate S6 in MCF-7 cells. Phosphorylation of the two p-S6Kinase isoforms (P85 and P70), and of pS6, was decreased following GLP-1 treatment. We conducted metabolomics screen using NMR and preliminary data indicated reduced lactic acid levels and increased glutamic acid levels following GLP-1 treatment.

Thus, we show that regulation of AKT-mTOR and AMPK metabolic pathways by GLP-1 in breast cancer, mediate GLP-1 growth inhibitory effect. As GLP-1 levels are lower in T2DM, we suggest this activity of GLP-1 as a novel link associating T2DM and breast cancer.

Citation Format: Tami Rubinek, Hagai Ligumsky, Avraham Karasik, Ido Wolf. Altered regulation of metabolic pathways by the hormone glucagon-like peptide 1 in breast cancer induces growth inhibition. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5388. doi:10.1158/1538-7445.AM2013-5388

The peptide-hormone glucagon-like peptide-1 activates cAMP and inhibits growth of breast cancer cells

The incretin hormone glucagon-like peptide (GLP)-1 is secreted from intestinal L cells in response to food intake, and promotes insulin secretion and pancreatic β-cell proliferation. Reduced GLP-1 levels are observed in obesity and type 2 diabetes mellitus (T2DM) and are associated with reduced insulin secretion and increased insulin resistance. GLP-1 mediates its activities through activation of a G-protein coupled receptor, which is expressed in the pancreas, as well as other tissues. Long-acting GLP-1 receptor (GLP-1R) agonists, such as exendin-4, are currently approved for the treatment of T2DM. As obesity and T2DM are associated with increased risk of breast cancer, we aimed to explore the effects of GLP-1 and exendin-4, on breast cancer cells. Treatment with GLP-1 or exendin-4 reduced viability and enhanced apoptosis of breast cancer cells but did not affect viability of nontumorigenic cells. Moreover, exendin-4 attenuated tumor formation by breast cancer cells in athymic mice. Treatment with either GLP-1 or exendin-4 elevated cAMP levels, activated the down-stream target CREB, and enhanced CRE promoter transcription, in breast cancer cells. Moreover, inhibition of exendin-4-induced adenylate cyclase activation restored cell viability, thus suggesting cAMP as a principle mediator of exendin-4 anti-tumorigenic activity. While the pancreatic form of the GLP-1R could not be detected in breast cancer cells, several lines of evidence indicated the existence of an alternative GLP-1R in mammary cells. Thus, internalization of GLP-1 into MCF-7 cells was evidenced, infection of MCF-7 cells with the pancreatic receptor enhanced proliferation, and treatment with exendin-(9-39), a GLP-1R antagonist, further increased cAMP levels. Our studies indicate the incretin hormone GLP-1 as a potent inducer of cAMP and an inhibitor of breast cancer cell proliferation. Reduced GLP-1 levels may, therefore, serve as a novel link between obesity, diabetes mellitus, and breast cancer.

Functional variant of KLOTHO: a breast cancer risk modifier among BRCA1 mutation carriers of Ashkenazi origin

Klotho is a transmembrane protein that can be shed and act as a circulating hormone and is a putative tumor suppressor in breast cancer. A functional variant of KLOTHO (KL-VS) contains two amino acid substitutions F352V and C370S and shows reduced activity. Germ-line mutations in BRCA1 and BRCA2 substantially increase lifetime risk of breast and ovarian cancers. Yet, penetrance of deleterious BRCA1 and BRCA2 mutations is incomplete even among carriers of identical mutations. We examined the association between KL-VS and cancer risk among 1115 Ashkenazi Jewish women: 236 non-carriers, 631 BRCA1 (185delAG, 5382insC) carriers and 248 BRCA2 (6174delT) carriers. Among BRCA1 carriers, heterozygosity for the KL-VS allele was associated with increased breast and ovarian cancer risk (hazard ratio 1.40, 95% confidence intervals 1.08-1.83, P=0.01) and younger age at breast cancer diagnosis (median age 48 vs 43 P=0.04). KLOTHO and BRCA2 are located on 13q12, and we identified linkage disequilibrium between KL-VS and BRCA2 6174delT mutation. Studies in breast cancer cells showed reduced growth inhibitory activity and reduced secretion of klotho F352V compared with wild-type klotho. These data suggest KL-VS as a breast and ovarian cancer risk modifier among BRCA1 mutation carriers. If validated in additional cohorts, the presence of KL-VS may serve as a predictor of cancer risk among BRCA1 mutation carriers.

Functional variant of the tumor suppressor klotho: a novel risk modifier for breast cancer among BRCA1/2 carriers

Abstract #1041

Background: The aging suppressor klotho is a transmembrane protein which is expressed in the kidneys, brain and hormone-responsive tissues and can be shed and act as a circulating hormone. The klotho gene is located on chromosome 13q12, about 700,000 base-pairs upstream to the BRCA2 gene. Klotho is a potent inhibitor of the insulin-like growth factor (IGF)-1 signaling pathway. We have recently found high klotho expression in normal breast tissue and low expression in breast cancer. Over-expression of klotho suppressed growth and inhibited the IGF-1 pathway in breast cancer cells. These data suggest klotho as a tumor suppressor gene in breast cancer. A single nucleotide polymorphism (SNP) in the klotho gene results in an amino acid substitution, F325V, which is associated with altered activity of klotho and reduced lifespan in human. As BRCA mutations may be associated with increased expression of IGF-1 and its receptor in breast cancer, we hypothesized that klotho functional variant may be associated with increased cancer risk among BRCA mutations carriers.&#x2028; Material and Methods: The presence of F325V variant was evaluated using exon-specific polymerase chain reaction followed by restriction enzyme analysis, in a cohort of 784 Israeli women consisting of 236 non-BRCA mutations carriers (healthy: 109, breast cancer: 94, ovarian cancer: 33), 340 BRCA1 185delAG and 5382insC mutation carriers (healthy: 138, breast cancer: 142, ovarian cancer: 60) and 208 BRCA2 6174delT carriers (healthy: 75, breast cancer: 106, ovarian cancer: 27).&#x2028; Results: Similar distribution of the F325V variant was noted in non-carriers and BRCA1 carriers (FF, wild-type 78%; FV, heterozygous 19%; VV, recessive 3%). However, F352V was over-represented among BRCA2 carriers: FF 25%, FV 50% and VV 25%. Analysis of additional SNPs indicated linkage disequilibrium between FV and BRCA2 6174delT mutation. Yet, among BRCA2 carriers, FF was significantly more frequent among healthy individuals compared to cancer patients (18% vs. 6% respectively, p=0.02). Surprisingly, among BRCA1 carriers FV status was associated with significantly younger age at breast cancer presentation compared to FF status (38±1.8 vs. 46±1.6 years respectively, p&lt;0.001). Association between FV status and age at ovarian cancer presentation among BRCA1 carriers could not be assessed due to small sample size. No association was noted between the klotho functional variant and age at presentation among non-carriers of BRCA mutations.&#x2028; Discussion: Taken together, these data suggest klotho F352V functional variant as a novel risk modifier among BRCA mutation carriers but not among non-carriers. As BRCA1/2 mutations can enhance and wild type klotho inhibits the activity of the IGF-1 signaling in cancer, it is possible that the presence of the less active variant of klotho attenuates this balance, thus leading to enhanced activation of the pathway. If validated by additional studies, the presence of the F352V klotho variant may serve as a predictor of cancer risk among BRCA mutation carriers and may also be a novel target for cancer therapy.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1041.

Klotho: a tumor suppressor and a modulator of the IGF-1 and FGF pathways in human breast cancer

Klotho is an anti-aging gene, which has been shown to inhibit the insulin and insulin-like growth factor 1 (IGF-1) pathways in mice hepatocytes and myocytes. As IGF-1 and insulin regulate proliferation, survival and metastasis of breast cancer, we studied klotho expression and activities in human breast cancer. Immunohistochemistry analysis of klotho expression in breast tissue arrays revealed high klotho expression in normal breast samples, but very low expression in breast cancer. In cancer samples, high klotho expression was associated with smaller tumor size and reduced KI67 staining. Forced expression of klotho reduced proliferation of MCF-7 and MDA-MB-231 breast cancer cells, whereas klotho silencing in MCF-7 cells, which normally express klotho, enhanced proliferation. Moreover, forced expression of klotho in these cells, or treatment with soluble klotho, inhibited the activation of IGF-1 and insulin pathways, and induced upregulation of the transcription factor CCAAT/enhancer-binding protein beta, a breast cancer growth inhibitor that is negatively regulated by the IGF-1-AKT axis. Co-immunoprecipitation revealed an interaction between klotho and the IGF-1 receptor. Klotho is also a known modulator of the fibroblast growth factor (FGF) pathway, a pathway that inhibits proliferation of breast cancer cells. Studies in breast cancer cells revealed increased activation of the FGF pathway by basic FGF following klotho overexpression. Klotho did not affect activation of the epidermal growth factor pathway in breast cancer cells. These data suggest klotho as a potential tumor suppressor and identify it as an inhibitor of the IGF-1 pathway and activator of the FGF pathway in human breast cancer.

Senescence mediates pituitary hypoplasia and restrains pituitary tumor growth

Understanding factors subserving pituitary cell proliferation enables understanding mechanisms underlying uniquely benign pituitary tumors. Pituitary tumor-transforming gene (Pttg) deletion results in pituitary hypoplasia, low pituitary cell proliferation rates, and rescue of pituitary tumor development in Rb(+/-) mice. Pttg(-/-) pituitary glands exhibit ARF/p53/p21-dependent senescence pathway activation evidenced by up-regulated p19, cyclin D1, and Bcl-2 protein levels and p53 stabilization. High pituitary p21 levels in the absence of PTTG were associated with suppressed cyclin-dependent kinase 2 activity, Rb phosphorylation, and cyclin A expression, all required for cell cycle progression. Although senescence-associated beta-galactosidase was enhanced in Pttg-deficient pituitary glands, telomere lengths were increased. DNA damage signaling pathways were activated and aneuploidy was evident in the Pttg-deficient pituitary, triggering senescence-associated genes. To confirm the p21 dependency of decreased proliferation and senescence in the Pttg-null pituitary, mouse embryonic fibroblast (MEF) colony formation was tested in wild-type, Pttg(-/-), Rb(+/-), Rb(+/-)Pttg(-/-), and Rb(+/-)Pttg(-/-)p21(-/-) cells. Rb(+/-)Pttg(-/-) MEFs, unlike Rb(+/-) cells, failed to produce colonies and exhibited high levels of senescence. p21 deletion from Rb(+/-)Pttg(-/-) MEFs enhanced anchorage-independent cell growth, accompanied by a marked decrease in senescence. As cell proliferation assessed by bromodeoxyuridine incorporation was higher in Rb(+/-)Pttg(-/-)p21(-/-) relative to Rb(+/-)Pttg(-/-) pituitary glands, p21-dependent senescence provoked by Pttg deletion may underlie pituitary hypoplasia and decreased tumor development in Rb(+/-)Pttg(-/-) mice.

Discordant proliferation and differentiation in pituitary tumor-transforming gene-null bone marrow stem cells

The mammalian securin, pituitary tumor-transforming gene ( Pttg), regulates sister chromatid separation during mitosis. Mice deficient in Pttg expression exhibit organ-specific hypoplasia of the testis, spleen, pituitary, and postmaturity pancreatic β-cells, pointing to a possible adult stem cell defect. Bone marrow stem cells (BMSCs) contribute to bone, cartilage, and fat tissue repair and regeneration, and multipotent adult progenitor cells (MAPCs) have broader differentiation ability. Bone marrow cells derived under MAPC conditions are involved in a spectrum of tissue repair. We therefore tested whether Pttg deletion affects stem cell proliferation and differentiation. BMSCs were isolated under MAPC conditions, although unlike MAPCs, wild-type (WT) and Pttg−/− BMSCs do not express octamer-binding transcription factor 4 and are stem cell antigen-I positive. WT and Pttg−/− cells did not differ in their ability to differentiate into adipogenic, osteogenic, or hepatocyte-like cells or in phenotypic markers. Cells underwent >100 population doublings, with no observed transforming events. Pttg-null BMSCs replicated 27% slower than WT BMSCs, and under hypoxic conditions, this difference widened. Although apoptosis was not enhanced in Pttg−/− cells, Pttg−/− BMSC senescence-associated β-galactosidase activity was elevated, consistent with enhanced p21 protein levels. Using gene array assays, DNA repair genes were shown to be upregulated in Pttg−/− BMSCs, whereas genes involved in cell cycle progression, including cyclin D1, were decreased. Separase, the protease regulated by Pttg, has been implicated in DNA damage repair and was downregulated in Pttg−/− BMSCs. Separase was constitutively phosphorylated in Pttg−/− cells, a modification likely serving as a compensatory mechanism for Pttg deletion. The results indicate that Pttg deletion reduces BMSC proliferation, renders cells more sensitive to hypoxia, and enhances senescent features, thus pointing to a role for Pttg in the maintenance and proliferation of BMSCs.

Mechanisms for Growth Factor-Induced Pituitary Tumor Transforming Gene-1 Expression in Pituitary Folliculostellate TtT/GF Cells

PTTG1, a securin protein, also behaves as a transforming gene and is overexpressed in pituitary tumors. Because pituitary folliculostellate (FS) cells regulate pituitary tumor growth factors by paracrine mechanisms, epidermal growth factor (EGF) receptor (EGFR)-mediated PTTG1 expression and cell proliferation was tested in pituitary FS TtT/GF cells. EGFR ligands caused up to 3-fold induction of Pttg1 mRNA expression, enhanced proliferating cell nuclear antigen, and increased entry of G0/1-arrested cells into S-phase. PTTG binding factor mRNA expression was not altered. EGF-induced Pttg1 expression and cell proliferation was abolished by preincubation of TtT/GF cells with EGFR inhibitors AG1478 and gefitinib. Phosphatidylinositol 3 kinase, protein kinase C, and MAPK, but not c-Jun N-terminal kinase and Janus activating kinase signaling regulated EGF-induced Pttg1, as well as proliferating cell nuclear antigen mRNA expression and entry into S-phase. EGF-induced EGFR and ERK1/2 phosphorylation was followed by rapid MAPK kinase/ERK kinase-dependent activation of Elk-1 and c-Fos. EGF-induced Pttg1 expression peaked at the S-G2 transition and declined thereafter. Pttg1 cell cycle dependency was confirmed by suppression of EGF-induced Pttg1 mRNA by blockade of cells in early S-phase. The results show that PTTG1 and its binding protein PTTG binding factor are expressed in pituitary FS TtT/GF cells. EGFR ligands induce PTTG1 and regulate S-phase, mediated by phosphatidylinositol 3 kinase, protein kinase C, and MAPK pathways. PTTG1 is therefore a target for EGFR-mediated paracrine regulation of pituitary cell growth.