PIK3CA/PTEN mutations and Akt activation as markers of sensitivity to allosteric mTOR inhibitors

Quantitative Assessment of Drug Efficacy and Emergence of Resistance in Patients with Metastatic Renal Cell Carcinoma Using a Longitudinal Exposure-Tumor Growth Inhibition Model: Apitolisib (Dual PI3K/mTORC1/2 Inhibitor) Versus Everolimus (mTORC1 Inhibitor)

Cancer remains a significant global health challenge, and despite remarkable advancements in therapeutic strategies, poor tolerability of drugs (causing dose reduction/interruptions) and/or the emergence of drug resistance are major obstacles to successful treatment outcomes. Metastatic renal cell carcinoma (mRCC) accounts for 2% of global cancer diagnoses and deaths. Despite the initial success of targeted therapies in mRCC, challenges remain to overcome drug resistance that limits the long-term efficacy of these treatments. Our analysis aim was to develop a semi-mechanistic longitudinal exposure-tumor growth inhibition model for patients with mRCC to characterize and compare everolimus (mTORC1) and apitolisib's (dual PI3K/mTORC1/2) ability to inhibit tumor growth, and quantitate each drug's efficacy decay caused by emergence of tumor resistance over time. Model-estimated on-treatment tumor growth rate constant was 1.7-fold higher for apitolisib compared to everolimus. Estimated half-life for loss of treatment effect over time for everolimus was 16.1 weeks compared to 7.72 weeks for apitolisib, suggesting a faster rate of tumor re-growth for apitolisib patients likely due to the emergence of resistance. Goodness-of-fit plots including visual predictive check indicated a good model fit and the model was able to capture individual tumor size-time profiles. Based on our knowledge, this is the first clinical report to quantitatively assess everolimus (mTORC1) and apitolisib (PI3K/mTORC1/2) efficacy decay in patients with mRCC. These results highlight the difference in overall efficacy of 2 drugs due to the quantified efficacy decay caused by emergence of resistance, and emphasize the importance of model-informed drug development for targeted cancer therapy.

HMGA1 sensitizes esophageal squamous cell carcinoma to mTOR inhibitors through the ETS1-FKBP12 axis

Esophageal carcinoma is amongst the prevalent malignancies worldwide, characterized by unclear molecular classifications and varying clinical outcomes. The PI3K/AKT/mTOR signaling, one of the frequently perturbed dysregulated pathways in human malignancies, has instigated the development of various inhibitory agents targeting this pathway, but many ESCC patients exhibit intrinsic or adaptive resistance to these inhibitors. Here, we aim to explore the reasons for the insensitivity of ESCC patients to mTOR inhibitors. We assessed the sensitivity to rapamycin in various ESCC cell lines by determining their respective IC50 values and found that cells with a low level of HMGA1 were more tolerant to rapamycin. Subsequent experiments have supported this finding. Through a transcriptome sequencing, we identified a crucial downstream effector of HMGA1, FKBP12, and found that FKBP12 was necessary for HMGA1-induced cell sensitivity to rapamycin. HMGA1 interacted with ETS1, and facilitated the transcription of FKBP12. Finally, we validated this regulatory axis in in vivo experiments, where HMGA1 deficiency in transplanted tumors rendered them resistance to rapamycin. Therefore, we speculate that mTOR inhibitor therapy for individuals exhibiting a reduced level of HMGA1 or FKBP12 may not work. Conversely, individuals exhibiting an elevated level of HMGA1 or FKBP12 are more suitable candidates for mTOR inhibitor treatment.

Discovery of novel potent PI3K/mTOR dual-target inhibitors based on scaffold hopping: Design, synthesis, and antiproliferative activity

The PI3K/AKT/mTOR pathway is one of the most common dysregulated signaling cascade responses in human cancers, playing a crucial role in cell proliferation and angiogenesis. Therefore, the development of anticancer drugs targeting the PI3K and mTOR pathways has become a research hotspot in cancer treatment. In this study, the PI3K selective inhibitor GDC-0941 was selected as a lead compound, and 28 thiophenyl-triazine derivatives with aromatic urea structures were synthesized based on scaffold hopping, serving as a novel class of PI3K/mTOR dual inhibitors. The most promising compound Y-2 was obtained through antiproliferative activity evaluation, kinase inhibition, and toxicity assays. The results showed that Y-2 demonstrated potential inhibitory effects on both PI3K kinase and mTOR kinase, with IC50 values of 171.4 and 10.2 nM, respectively. The inhibitory effect of Y-2 on mTOR kinase was 52 times greater than that of the positive drug GDC-0941. Subsequently, the antitumor activity of Y-2 was verified through pharmacological experiments such as AO staining, cell apoptosis, scratch assays, and cell colony formation. The antitumor mechanism of Y-2 was further investigated through JC-1 experiments, real-time quantitative PCR, and Western blot analysis. Based on the above experiments, Y-2 can be identified as a potent PI3K/mTOR dual inhibitor for cancer treatment.

Signaling Pathways mTOR and ERK as Therapeutic Targets in Sinonasal Intestinal-Type Adenocarcinoma

Despite advances in surgery and radiotherapy, the overall prognosis of sinonasal intestinal-type adenocarcinoma (ITAC) is poor, and new treatment options are needed. Recent studies have indicated alterations in cellular signaling pathways that may serve as targets for modern inhibitors. Our aim was to evaluate the frequency of mTOR and ERK pathway upregulation in a retrospective series of 139 ITAC and to test the efficacy and mechanism of action of candidate targeted inhibitors in cell line ITAC-3. An immunohistochemical analysis on p-AKT, p-mTOR, p-S6, p-4E-BP1, and p-ERK indicated, respectively, a 68% and 57% mTOR and ERK pathway activation. In vitro studies using low doses of mTOR inhibitor everolimus and ERK inhibitor selumetinib showed significant growth inhibition as monotherapy and especially as combined therapy. This effect was accompanied by the downregulation of mTOR and ERK protein expression. Our data open a new and promising possibility for personalized treatment of ITAC patients.

Targeting signaling pathways in osteosarcoma: Mechanisms and clinical studies

Osteosarcoma (OS) is a highly prevalent bone malignancy among adolescents, accounting for 40% of all primary malignant bone tumors. Neoadjuvant chemotherapy combined with limb-preserving surgery has effectively reduced patient disability and mortality, but pulmonary metastases and OS cells' resistance to chemotherapeutic agents are pressing challenges in the clinical management of OS. There has been an urgent need to identify new biomarkers for OS to develop specific targeted therapies. Recently, the continued advancements in genomic analysis have contributed to the identification of clinically significant molecular biomarkers for diagnosing OS, acting as therapeutic targets, and predicting prognosis. Additionally, the contemporary molecular classifications have revealed that the signaling pathways, including Wnt/β-catenin, PI3K/AKT/mTOR, JAK/STAT3, Hippo, Notch, PD-1/PD-L1, MAPK, and NF-κB, have an integral role in OS onset, progression, metastasis, and treatment response. These molecular classifications and biological markers have created new avenues for more accurate OS diagnosis and relevant treatment. We herein present a review of the recent findings for the modulatory role of signaling pathways as possible biological markers and treatment targets for OS. This review also discusses current OS therapeutic approaches, including signaling pathway-based therapies developed over the past decade. Additionally, the review covers the signaling targets involved in the curative effects of traditional Chinese medicines in the context of expression regulation of relevant genes and proteins through the signaling pathways to inhibit OS cell growth. These findings are expected to provide directions for integrating genomic, molecular, and clinical profiles to enhance OS diagnosis and treatment.

A nanotherapeutic strategy that engages cytotoxic and immunosuppressive activities for the treatment of cancer recurrence following organ transplantation

BACKGROUND

Long-term treatment with immunosuppressants is necessary to attenuate allograft rejection following organ transplantation (OT). Consequently, the overall survival of OT recipients with malignancies has been substantially compromised by tumour recurrence. Rapamycin (RAPA) is a clinically approved immunosuppressive agent with antitumour activity that is considered beneficial in preventing posttransplant tumour recurrence. However, the clinical outcome of RAPA is impeded by acquired drug resistance and its poor oral bioavailability.

METHODS

A nanotherapeutic strategy was developed by supramolecular assembly of RAPA into a polymer cytotoxic 7-ethyl-10-hydroxycamptothecin (SN38) prodrug nanoparticle (termed SRNP) for simultaneous codelivery of cytotoxic/immunosuppressive agents. Cell-based experiments were used to evaluate the cytotoxicity of SRNPs against hepatocellular carcinoma (HCC). The therapeutic efficacy of SRNPs was evaluated in multiple preclinical models including an orthotopic HCC mouse model, an orthotopic liver transplantation (OLT) rat model and a clinically relevant cancer-transplant model to examine its antitumour and immunosuppressive activity.

FINDINGS

The combination of SN38 with RAPA resulted in synergetic effects against HCC cells and alleviated RAPA resistance by abrogating Akt/mTOR signalling activation. SRNPs exhibited potent antitumour efficiency in the orthotopic HCC model while substantially prolonging the survival of allografts in the OLT model. In the cancer-transplant model that simultaneously bears tumour xenografts and skin allografts, SRNPs not only effectively inhibited tumour growth but also attenuated allograft damage.

INTERPRETATION

The nanotherapy presented here had enhanced efficacy against tumours and maintained satisfactory immunosuppressive activity and thus has great potential to improve the survival outcomes of patients with a high risk of tumour recurrence following OT.

FUNDING

This work was supported by the National Natural Science Foundation of China (32171368 and 31671019), the Zhejiang Provincial Natural Science Foundation of China (LZ21H180001), the Zhejiang Province Preeminence Youth Fund (LR19H160002), and the Jinan Provincial Laboratory Research Project of Microecological Biomedicine (JNL-2022039c).

Strategies to Re-Sensitize Castration-Resistant Prostate Cancer to Antiandrogen Therapy

Since prostate cancer (PCa) was described as androgen-dependent, the androgen receptor (AR) has become the mainstay of its systemic treatment: androgen deprivation therapy (ADT). Although, through recent years, more potent drugs have been incorporated, this chronic AR signaling inhibition inevitably led the tumor to an incurable phase of castration resistance. However, in the castration-resistant status, PCa cells remain highly dependent on the AR signaling axis, and proof of it is that many men with castration-resistant prostate cancer (CRPC) still respond to newer-generation AR signaling inhibitors (ARSis). Nevertheless, this response is limited in time, and soon, the tumor develops adaptive mechanisms that make it again nonresponsive to these treatments. For this reason, researchers are focused on searching for new alternatives to control these nonresponsive tumors, such as: (1) drugs with a different mechanism of action, (2) combination therapies to boost synergies, and (3) agents or strategies to resensitize tumors to previously addressed targets. Taking advantage of the wide variety of mechanisms that promote persistent or reactivated AR signaling in CRPC, many drugs explore this last interesting behavior. In this article, we will review those strategies and drugs that are able to resensitize cancer cells to previously used treatments through the use of "hinge" treatments with the objective of obtaining an oncological benefit. Some examples are: bipolar androgen therapy (BAT) and drugs such as indomethacin, niclosamide, lapatinib, panobinostat, clomipramine, metformin, and antisense oligonucleotides. All of them have shown, in addition to an inhibitory effect on PCa, the rewarding ability to overcome acquired resistance to antiandrogenic agents in CRPC, resensitizing the tumor cells to previously used ARSis.

18F-FDG and 18F-FLT Uptake Profiles for Breast Cancer Cell Lines Treated with Targeted PI3K/Akt/mTOR Therapies

Background: To evaluate ¹⁸F-fluoro-2-deoxy-glucose (¹⁸F-FDG) and ¹⁸F-fluorothymidine (¹⁸F-FLT) as early-response biomarkers for phosphoinositide-3-kinase/Akt/mammalian-target-of-rapamycin (PI3K/Akt/mTOR) inhibition in breast cancer (BC) models. Materials and Methods: Two human epidermal growth factor receptor 2 (HER2)-positive (trastuzumab-sensitive SKBR3; trastuzumab-resistant JIMT1) and one triple-negative BC cell line (MDA-MB-231, trastuzumab, and everolimus resistant) were treated with trastuzumab (HER2 antagonist), PIK90 (PI3K inhibitor), or everolimus (mTOR inhibitor). Radiotracer uptake was measured before, 24, and 72 h after drug exposure and correlated with changes in cell number, glucose transporter 1 (GLUT1), cell cycle phase, and downstream signaling activation. Results: In responsive cells, cell number correlated with ¹⁸F-FLT at 24 h and ¹⁸F-FDG at 72 h of drug exposure, except in JIMT1 treated with everolimus, where both radiotracers failed to detect response owing to a temporary increase in tracer uptake. This flare can be caused by reflex activation of Akt combined with a hyperactive insulin-like growth factor I receptor (IGF-1R) signaling, resulting in increased trafficking of GLUTs to the cell membrane (¹⁸F-FDG) and enhanced DNA repair (¹⁸F-FLT). In resistant cells, no major changes were observed, although a nonsignificant flair for both tracers was observed in JIMT1 treated with trastuzumab. Conclusion: ¹⁸F-FLT positron emission tomography (PET) detects response to PI3K-targeting therapy earlier than ¹⁸F-FDG PET in BC cells. However, therapy response can be underestimated after trastuzumab and everolimus owing to negative feedback loop and crosstalk between pathways.

Signaling pathways and therapeutic interventions in gastric cancer

Gastric cancer (GC) ranks fifth in global cancer diagnosis and fourth in cancer-related death. Despite tremendous progress in diagnosis and therapeutic strategies and significant improvements in patient survival, the low malignancy stage is relatively asymptomatic and many GC cases are diagnosed at advanced stages, which leads to unsatisfactory prognosis and high recurrence rates. With the recent advances in genome analysis, biomarkers have been identified that have clinical importance for GC diagnosis, treatment, and prognosis. Modern molecular classifications have uncovered the vital roles that signaling pathways, including EGFR/HER2, p53, PI3K, immune checkpoint pathways, and cell adhesion signaling molecules, play in GC tumorigenesis, progression, metastasis, and therapeutic responsiveness. These biomarkers and molecular classifications open the way for more precise diagnoses and treatments for GC patients. Nevertheless, the relative significance, temporal activation, interaction with GC risk factors, and crosstalk between these signaling pathways in GC are not well understood. Here, we review the regulatory roles of signaling pathways in GC potential biomarkers, and therapeutic targets with an emphasis on recent discoveries. Current therapies, including signaling-based and immunotherapies exploited in the past decade, and the development of treatment for GC, particularly the challenges in developing precision medications, are discussed. These advances provide a direction for the integration of clinical, molecular, and genomic profiles to improve GC diagnosis and treatments.

Therapeutic strategies for patients with neuroendocrine neoplasms: current perspectives

INTRODUCTION

Neuroendocrine neoplasms (NENs) are a heterogeneous group of malignancies mainly arising in the gastroenteropancreatic (GEP) and bronchopulmonary systems, with steadily increasing incidence. The therapeutic landscape has widened and the therapeutic strategy should be based on new sequences and combinations, still debated.

AREAS COVERED

Herein, we provide an overview of current approved pharmacological treatments in patients with NENs, with the aim to summarize evidence of efficacy of the main different options in GEP and pulmonary NENs, principally focusing on somatostatin analogs (SSAs), targeted therapy with everolimus and sunitinib, peptide receptor radionuclide therapy (PRRT) and chemotherapy. We discuss biological rationale and toxicities, including current indications according to differentiation and placement in the therapeutic algorithm, clinical trials, and combinations. Furthermore, we recommend areas for further research.

EXPERT OPINION

Therapeutic management of patients with NENs represents a challenge for clinicians and the identification of effective sequences and combinations is of utmost importance. Major efforts should be directed to early identify and overcome resistance and to limit toxicity. The progress in the therapeutic management of NENs grows faster and the choice of the best approach should be based on randomized clinical trials, as well as on long-term, real-world data.

Prognostic and Predictive Role of Body Composition in Metastatic Neuroendocrine Tumor Patients Treated with Everolimus: A Real-World Data Analysis

Neuroendocrine tumors (NETs) are rare neoplasms frequently characterized by an upregulation of the mammalian rapamycin targeting (mTOR) pathway resulting in uncontrolled cell proliferation. The mTOR pathway is also involved in skeletal muscle protein synthesis and in adipose tissue metabolism. Everolimus inhibits the mTOR pathway, resulting in blockade of cell growth and tumor progression. The aim of this study is to investigate the role of body composition indexes in patients with metastatic NETs treated with everolimus. The study population included 30 patients with well-differentiated (G1-G2), metastatic NETs treated with everolimus at the IRCCS Romagnolo Institute for the Study of Tumors (IRST) “Dino Amadori”, Meldola (FC), Italy. The body composition indexes (skeletal muscle index [SMI] and adipose tissue indexes) were assessed by measuring on a computed tomography (CT) scan the cross-sectional area at L3 at baseline and at the first radiological assessment after the start of treatment. The body mass index (BMI) was assessed at baseline. The median progression-free survival (PFS) was 8.9 months (95% confidence interval [CI]: 3.4–13.7 months). The PFS stratified by tertiles was 3.2 months (95% CI: 0.9–10.1 months) in patients with low SMI (tertile 1), 14.2 months (95% CI: 2.3 months-not estimable [NE]) in patients with intermediate SMI (tertile 2), and 9.1 months (95% CI: 2.7 months-NE) in patients with high SMI (tertile 3) (p = 0.039). Similarly, the other body composition indexes also showed a statistically significant difference in the three groups on the basis of tertiles. The median PFS was 3.2 months (95% CI: 0.9–6.7 months) in underweight patients (BMI ≤ 18.49 kg/m2) and 10.1 months (95% CI: 3.7–28.4 months) in normal-weight patients (p = 0.011). There were no significant differences in terms of overall survival. The study showed a correlation between PFS and the body composition indexes in patients with NETs treated with everolimus, underlining the role of adipose and muscle tissue in these patients.

Targeting SHP2 phosphatase in breast cancer overcomes RTK-mediated resistance to PI3K inhibitors

Background

PI3K signaling is frequently activated in breast cancer and is targeted by PI3K inhibitors. However, resistance of tumor cells to PI3K inhibition, often mediated by activated receptor tyrosine kinases, is commonly observed and reduces the potency of PI3K inhibitors. Therefore, new treatment strategies to overcome resistance to PI3K inhibitors are urgently needed to boost their efficacy. The phosphatase SHP2, which plays a crucial role in mediating signal transduction between receptor tyrosine kinases and both the PI3K and MAPK pathways, is a potential target for combination treatment.

Methods

We tested combinations of PI3K and SHP2 inhibitors in several experimental breast cancer models that are resistant to PI3K inhibition. Using cell culturing, biochemical and genetic approaches, we evaluated tumor cell proliferation and signaling output in cells treated with PI3K and SHP2 inhibitors.

Results

Combination treatment with PI3K and SHP2 inhibitors counteracted both acquired and intrinsic breast cancer cell resistance to PI3K inhibition that is mediated by activated receptor tyrosine kinases. Dual PI3K and SHP2 inhibition blocked proliferation and led to sustained inactivation of PI3K and MAPK signaling, where resistant cells rapidly re-activated these pathways upon PI3K inhibitor monotreatment. In addition, we demonstrate that overexpression of SHP2 induced resistance to PI3K inhibition, and that SHP2 was frequently activated during the development of PI3K inhibitor resistance after prolonged treatment of sensitive cells.

Conclusions

Our results highlight the importance of SHP2 as a player in resistance to PI3K inhibitors. Combination treatment with PI3K and SHP2 inhibitors could pave the way for significant improvements in therapies for breast cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13058-022-01521-3.

Silybum marianum total extract, silymarin and silibinin abate hepatocarcinogenesis and hepatocellular carcinoma growth via modulation of the HGF/c-Met, Wnt/β-catenin, and PI3K/Akt/mTOR signaling pathways

Hepatocellular carcinoma (HCC) has been identified as one of the most deadly malignancies with limited therapeutic efficacy worldwide. However, understanding the molecular mechanisms of crosstalk between signaling pathways in HCC and predicting cancer cell responses to targeted therapeutic interventions remain to be challenge. Thus, in this study, we aimed to evaluate the anticancerous efficacy of Silybum marianum total extract (STE), silymarin (Sm), and silibinin (Sb) against experimentally-induced HCC in rats. In vitro investigations were also performed and the anticancer effects against HCC cell lines (HepG2 and Huh7) were confirmed. Wistar rats were given diethylnitrosamine (DEN)/2-acetylaminofluorene (AAF)/carbon tetrachloride (CCl4) and were orally treated with STE (200 mg/kg body weight (bw)), Sm (150 mg/kg bw), and Sb (5 mg/kg bw) every other day from the 1st or 16th week to the 25th week of DEN/AAF/CCl4 injection. Treatment with STE, Sm, and Sb inhibited the growth of cancerous lesions in DEN/AAF/CCl4-treated rats. This inhibition was associated with inhibition of Ki-67 expression and repression of HGF/cMet, Wnt/β-catenin, and PI3K/Akt/mTOR signaling pathways. STE, Sm, and Sb improved liver function biomarkers and tumor markers (AFP, CEA, and CA19.9) and increased total protein and albumin levels in serum. STE, Sm, and Sb treatment was also noted to reduce the hepatic production of lipid peroxides, increase hepatic glutathione content, and induce the activities of hepatic antioxidant enzymes in DEN/AAF/CCl4-treated rats. These results indicate that STE, Sm, and Sb exert anti-HCC effects through multiple pathways, including suppression of Ki-67 expression and HGF/cMet, Wnt/β-catenin, and PI3K/Akt/mTOR pathways and enhancement of antioxidant defense mechanisms.

PTEN downregulation induces apoptosis and cell cycle arrest in uterine cervical cancer cells

The tumor suppressors PTEN and p53 are often downregulated in various human cancer types, which has been associated with a poor prognosis. Recent evidence implies that PTEN downregulation may induce growth arrest of kidney cells and cancer cells. In the present study, the role of PTEN in the proliferation and survival of cervical cancer cells was investigated. It was found that PTEN silencing promoted apoptosis and cell-cycle arrest, accompanied by a significant decrease in the proportion of cells in the S1 phase of the cell cycle. Moreover, PTEN silencing in cervical cancer cells increased levels of p53, p27, p21, phospho-ERK and cleaved caspase-3, and decreased levels of cyclin A2 and cyclin D1. Furthermore, PTEN knockdown significantly impacted the viability of cervical cancer cells. P53 silencing did not affect the ability of PTEN knockdown to induce apoptosis in cervical cancer cells. Taken together, the present study results imply that PTEN silencing induces apoptosis and decreases proliferation in cervical cancer cells; hence, PTEN inhibition may represent a promising strategy for the treatment of cervical cancer.

Clinicopathological and Genomic Profiles of Atypical Fibroxanthoma and Pleomorphic Dermal Sarcoma Identify Overlapping Signatures with a High Mutational Burden

Atypical fibroxanthoma (AFX) and pleomorphic dermal sarcoma (PDS) are rare tumors developing in chronically sun-exposed skin. Clinicopathological features are similar, but they differ in prognosis, while PDS has a more aggressive course with a higher risk for local recurrence and metastases. In current clinical practice, they are diagnosed by exclusion using immunohistochemistry. Thus, stringent diagnostic criteria and correct differentiation are critical in management and treatment for optimal outcomes. This retrospective single-center study collected clinicopathological data and tumor samples of 10 AFX and 18 PDS. Extracted genomic DNA from tumor specimens was analyzed by a next-generation sequencing (NGS) platform (FoundationOne-CDx™). Among 65 identified mutations, TP53 inactivating mutations were observed in all tumor specimens. In both AFX and PDS, the known pathogenic gene alterations in CDKN2A, TERT promoter, and NOTCH1 were frequently present, along with high mutational burden and stable Micro-Satellite Instability status. The mutational profiles differed only in ASXL1, which was only present in AFX. Further differences were identified in likely pathogenic and unknown gene alterations. Similarities in their genomic signatures could help to distinguish them from other malignancies, but they are not distinguishable between each other using the FoundationOne-CDx™ NGS panel. Therefore, histological criteria to determine diagnosis remain valid. For further insight, performing deep tumor profiling may be necessary.

Deciphering the signaling network of breast cancer improves drug sensitivity prediction

One goal of precision medicine is to tailor effective treatments to patients' specific molecular markers of disease. Here, we used mass cytometry to characterize the single-cell signaling landscapes of 62 breast cancer cell lines and five lines from healthy tissue. We quantified 34 markers in each cell line upon stimulation by the growth factor EGF in the presence or absence of five kinase inhibitors. These data-on more than 80 million single cells from 4,000 conditions-were used to fit mechanistic signaling network models that provide insight into how cancer cells process information. Our dynamic single-cell-based models accurately predicted drug sensitivity and identified genomic features associated with drug sensitivity, including a missense mutation in DDIT3 predictive of PI3K-inhibition sensitivity. We observed similar trends in genotype-drug sensitivity associations in patient-derived xenograft mouse models. This work provides proof of principle that patient-specific single-cell measurements and modeling could inform effective precision medicine strategies.

High frequency of PIK3CA and TERT promoter mutations in fibromatosis-like spindle cell carcinomas

AIMS

Fibromatosis-like spindle cell carcinomas (FLSCCs) are rare metaplastic breast cancers (MBCs) that are characterised by bland spindle cells in a collagenous stroma. Although some MBCs are highly malignant, FLSCCs have indolent behaviour with low potential for lymph node or distant metastasis. Owing to their rarity, there are limited genomic data on FLSCCs. In this study, we analysed the clinicopathological features and molecular characteristics of four FLSCCs to elucidate the pathogenesis of these rare tumours.

METHODS AND RESULTS

Four pure FLSCCs were sequenced by DIAN (Hangzhou Lab) using a 324-gene platform (FoundationOne CDx) with licensed technologies. The results showed that most FLSCCs harboured the pathogenic H1047R mutation in PIK3CA (3/4, 75%) and the -124C>T mutation in the telomerase reverse transcriptase (TERT) promoter (3/4, 75%). No copy number variations were observed in any cases in our study.

CONCLUSIONS

Our study showed that PIK3CA and TERT promoter mutations were common genetic features of FLSCCs. These findings contribute to our understanding of FLSCCs biology.

Combining Neratinib with CDK4/6, mTOR, and MEK Inhibitors in Models of HER2-positive Cancer

PURPOSE

Neratinib is an irreversible, pan-HER tyrosine kinase inhibitor that is FDA approved for HER2-overexpressing/amplified (HER2+) breast cancer. In this preclinical study, we explored the efficacy of neratinib in combination with inhibitors of downstream signaling in HER2+ cancers in vitro and in vivo.

EXPERIMENTAL DESIGN

Cell viability, colony formation assays, and Western blotting were used to determine the effect of neratinib in vitro. In vivo efficacy was assessed with patient-derived xenografts (PDX): two breast, two colorectal, and one esophageal cancer (with HER2 mutations). Four PDXs were derived from patients who received previous HER2-targeted therapy. Proteomics were assessed through reverse phase protein arrays and network-level adaptive responses were assessed through Target Score algorithm.

RESULTS

In HER2+ breast cancer cells, neratinib was synergistic with multiple agents, including mTOR inhibitors everolimus and sapanisertib, MEK inhibitor trametinib, CDK4/6 inhibitor palbociclib, and PI3Kα inhibitor alpelisib. We tested efficacy of neratinib with everolimus, trametinib, or palbociclib in five HER2+ PDXs. Neratinib combined with everolimus or trametinib led to a 100% increase in median event-free survival (EFS; tumor doubling time) in 25% (1/4) and 60% (3/5) of models, respectively, while neratinib with palbociclib increased EFS in all five models. Network analysis of adaptive responses demonstrated upregulation of EGFR and HER2 signaling in response to CDK4/6, mTOR, and MEK inhibition, possibly providing an explanation for the observed synergies with neratinib.

CONCLUSIONS

Taken together, our results provide strong preclinical evidence for combining neratinib with CDK4/6, mTOR, and MEK inhibitors for the treatment of HER2+ cancer.

G3BPs tether the TSC complex to lysosomes and suppress mTORC1 signaling

Ras GTPase-activating protein-binding proteins 1 and 2 (G3BP1 and G3BP2, respectively) are widely recognized as core components of stress granules (SGs). We report that G3BPs reside at the cytoplasmic surface of lysosomes. They act in a non-redundant manner to anchor the tuberous sclerosis complex (TSC) protein complex to lysosomes and suppress activation of the metabolic master regulator mechanistic target of rapamycin complex 1 (mTORC1) by amino acids and insulin. Like the TSC complex, G3BP1 deficiency elicits phenotypes related to mTORC1 hyperactivity. In the context of tumors, low G3BP1 levels enhance mTORC1-driven breast cancer cell motility and correlate with adverse outcomes in patients. Furthermore, G3bp1 inhibition in zebrafish disturbs neuronal development and function, leading to white matter heterotopia and neuronal hyperactivity. Thus, G3BPs are not only core components of SGs but also a key element of lysosomal TSC-mTORC1 signaling.

Molecular Features of Cancers Exhibiting Exceptional Responses to Treatment

A small fraction of cancer patients with advanced disease survive significantly longer than patients with clinically comparable tumors. Molecular mechanisms for exceptional responses to therapy have been identified by genomic analysis of tumor biopsies from individual patients. Here, we analyzed tumor biopsies from an unbiased cohort of 111 exceptional responder patients using multiple platforms to profile genetic and epigenetic aberrations as well as the tumor microenvironment. Integrative analysis uncovered plausible mechanisms for the therapeutic response in nearly a quarter of the patients. The mechanisms were assigned to four broad categories-DNA damage response, intracellular signaling, immune engagement, and genetic alterations characteristic of favorable prognosis-with many tumors falling into multiple categories. These analyses revealed synthetic lethal relationships that may be exploited therapeutically and rare genetic lesions that favor therapeutic success, while also providing a wealth of testable hypotheses regarding oncogenic mechanisms that may influence the response to cancer therapy.

Characterization of Mutational Status, Spheroid Formation, and Drug Response of a New Genomically-Stable Human Ovarian Clear Cell Carcinoma Cell Line, 105C

Ovarian clear cell carcinoma (OCCC) is a rare subtype of gynecological cancer for which well-characterized and authenticated model systems are scarce. We provide an extensive characterization of ‘105C’, a cell line generated from an adenocarcinoma of the clear cell histotype using targeted next-generation sequencing, cytogenetic microarrays, along with analyses of AKT/mTOR signaling. We report that that the 105C cell line is a bona fide OCCC cell line, carrying PIK3CA, PTEN, and ARID1A gene mutations, consistent with OCCC, yet maintain a stable genome as reflected by low copy number variation. Unlike KOC-7c, TOV-21G, and RMG-V OCCC lines also mutated for the above genes, the 105C cells do not carry mutations in mismatch repair genes. Importantly, we show that 105C cells exhibit greater resistance to mTOR inhibition and carboplatin treatment compared to 9 other OCCC cell lines in 3D spheroid cultures. This resistance may be attributed to 105C cells remaining dormant in suspension culture which surprisingly, contrasts with several other OCCC lines which continue to proliferate in long-term suspension culture. 105C cells survive xenotransplantation but do not proliferate and metastasize. Collectively, we show that the 105C OCCC cell line exhibits unique properties useful for the pre-clinical investigation of OCCC pathobiology.

Phase 2 study of buparlisib (BKM120), a pan-class I PI3K inhibitor, in patients with metastatic triple-negative breast cancer

BACKGROUND

Treatment options for triple-negative breast cancer remain limited. Activation of the PI3K pathway via loss of PTEN and/or INPP4B is common. Buparlisib is an orally bioavailable, pan-class I PI3K inhibitor. We evaluated the safety and efficacy of buparlisib in patients with metastatic triple-negative breast cancer.

METHODS

This was a single-arm phase 2 study enrolling patients with triple-negative metastatic breast cancer. Patients were treated with buparlisib at a starting dose of 100 mg daily. The primary endpoint was clinical benefit, defined as confirmed complete response (CR), partial response (PR), or stable disease (SD) for ≥ 4 months, per RECIST 1.1. Secondary endpoints included progression-free survival (PFS), overall survival (OS), and toxicity. A subset of patients underwent pre- and on-treatment tumor tissue biopsies for correlative studies.

RESULTS

Fifty patients were enrolled. Median number of cycles was 2 (range 1-10). The clinical benefit rate was 12% (6 patients, all SD ≥ 4 months). Median PFS was 1.8 months (95% confidence interval [CI] 1.6-2.3). Median OS was 11.2 months (95% CI 6.2-25). The most frequent adverse events were fatigue (58% all grades, 8% grade 3), nausea (34% all grades, none grade 3), hyperglycemia (34% all grades, 4% grade 3), and anorexia (30% all grades, 2% grade 3). Eighteen percent of patients experienced depression (12% grade 1, 6% grade 2) and anxiety (10% grade 1, 8% grade 2). Alterations in PIK3CA/AKT1/PTEN were present in 6/27 patients with available targeted DNA sequencing (MSK-IMPACT), 3 of whom achieved SD as best overall response though none with clinical benefit ≥ 4 months. Of five patients with paired baseline and on-treatment biopsies, reverse phase protein arrays (RPPA) analysis demonstrated reduction of S6 phosphorylation in 2 of 3 patients who achieved SD, and in none of the patients with progressive disease.

CONCLUSIONS

Buparlisib was associated with prolonged SD in a very small subset of patients with triple-negative breast cancer; however, no confirmed objective responses were observed. Downmodulation of key nodes in the PI3K pathway was observed in patients who achieved SD. PI3K pathway inhibition alone may be insufficient as a therapeutic strategy for triple-negative breast cancer.

TRIAL REGISTRATION

NCT01790932 . Registered on 13 February 2013; NCT01629615 . Registered on 27 June 2012.

Deubiquitinase OTUD5 is a positive regulator of mTORC1 and mTORC2 signaling pathways

The mammalian Target of Rapamycin (mTOR) pathway regulates a variety of physiological processes, including cell growth and cancer progression. The regulatory mechanisms of these signals are extremely complex and comprise many feedback loops. Here, we identified the deubiquitinating enzyme ovarian tumor domain-containing protein 5 (OTUD5) as a novel positive regulator of the mTOR complex (mTORC) 1 and 2 signaling pathways. We demonstrated that OTUD5 stabilized β-transducin repeat-containing protein 1 (βTrCP1) proteins via its deubiquitinase (DUB) activity, leading to the degradation of Disheveled, Egl-10, and pleckstrin domain-containing mTOR-interacting protein (DEPTOR), which is an inhibitory protein of mTORC1 and 2. We also showed that mTOR directly phosphorylated OTUD5 and activated its DUB activity. RNA sequencing analysis revealed that OTUD5 regulates the downstream gene expression of mTOR. Additionally, OTUD5 depletion elicited several mTOR-related phenotypes such as decreased cell size and increased autophagy in mammalian cells as well as the suppression of a dRheb-induced curled wing phenotype by RNA interference of Duba, a fly ortholog of OTUD5, in Drosophila melanogaster. Furthermore, OTUD5 knockdown inhibited the proliferation of the cancer cell lines with mutations activating mTOR pathway. Our results suggested a positive feedback loop between OTUD5 and mTOR signaling pathway.

Resistance to second generation antiandrogens in prostate cancer: pathways and mechanisms

Androgen deprivation therapy targeting the androgens/androgen receptor (AR) signaling continues to be the mainstay treatment of advanced-stage prostate cancer. The use of second-generation antiandrogens, such as abiraterone acetate and enzalutamide, has improved the survival of prostate cancer patients; however, a majority of these patients progress to castration-resistant prostate cancer (CRPC). The mechanisms of resistance to antiandrogen treatments are complex, including specific mutations, alternative splicing, and amplification of oncogenic proteins resulting in dysregulation of various signaling pathways. In this review, we focus on the major mechanisms of acquired resistance to second generation antiandrogens, including AR-dependent and AR-independent resistance mechanisms as well as other resistance mechanisms leading to CRPC emergence. Evolving knowledge of resistance mechanisms to AR targeted treatments will lead to additional research on designing more effective therapies for advanced-stage prostate cancer.

Combined p53- and PTEN-deficiency activates expression of mesenchyme homeobox 1 (MEOX1) required for growth of triple-negative breast cancer

Triple-negative breast cancer (TNBC) is an aggressive cancer subtype for which effective therapies are unavailable. TNBC has a high frequency of tumor protein p53 (Tp53/p53)- and phosphatase and tensin homolog (PTEN) deficiencies, and combined p53- and PTEN-deficiency is associated with poor prognosis and poor response to anticancer therapies. In this study, we discovered that combined p53- and PTEN-deficiency in TNBC activates expression of the transcription factor mesenchyme homeobox 1 (MEOX1). We found that MEOX1 is expressed only in TNBC cells with frequent deficiencies in p53 and PTEN, and that its expression is undetectable in luminal A, luminal B, and HER2+ subtypes, as well as in normal breast cells with wild-type (WT) p53 and PTEN. Notably, siRNA knockdown of both p53 and PTEN activated MEOX1 expression in breast cancer cells, whereas individual knockdowns of either p53 or PTEN had only minimal effects on MEOX1 expression. MEOX1 knockdown abolished cell proliferation of p53- and PTEN-deficient TNBC in vitro and inhibited tumor growth in vivo, but had no effect on the proliferation of luminal and HER2+ cancer cells and normal breast cells. RNA-Seq and immunoblotting analyses showed that MEOX1 knockdown decreased expression of tyrosine kinase 2 (TYK2), signal transducer and activator of transcription 5B (STAT5B), and STAT6 in p53- and PTEN-deficient TNBC cells. These results reveal the effects of combined p53- and PTEN-deficiency on MEOX1 expression and TNBC cell proliferation, suggesting that MEOX1 may serve as a potential therapeutic target for managing p53- and PTEN-deficient TNBC.

PTEN suppresses epithelial-mesenchymal transition and cancer stem cell activity by downregulating Abi1

The epithelial–mesenchymal transition (EMT) is an embryonic program frequently reactivated during cancer progression and is implicated in cancer invasion and metastasis. Cancer cells can also acquire stem cell properties to self-renew and give rise to new tumors through the EMT. Inactivation of the tumor suppressor PTEN has been shown to induce the EMT, but the underlying molecular mechanisms are less understood. In this study, we reconstituted PTEN-deficient breast cancer cells with wild-type and mutant PTEN, demonstrating that restoration of PTEN expression converted cancer cells with mesenchymal traits to an epithelial phenotype and inhibited cancer stem cell (CSC) activity. The protein rather than the lipid phosphatase activity of PTEN accounts for the reversal of the EMT. PTEN dephosphorylates and downregulates Abi1 in breast cancer cells. Gain- and loss-of-function analysis indicates that upregulation of Abi1 mediates PTEN loss-induced EMT and CSC activity. These results suggest that PTEN may suppress breast cancer invasion and metastasis via dephosphorylating and downregulating Abi1.

Clinical Evaluation of Everolimus in the Treatment of Neuroendocrine Tumors of the Lung: Patient Selection and Special Considerations. A Systematic and Critical Review of the Literature

Neuroendocrine tumors (NETs) of the lung are well-differentiated neuroendocrine neoplasms (NENs) with a heterogeneous clinical behaviour. Unlike gastroenteropancreatic NENs where therapeutic armamentarium clearly increased over the last decade, everolimus represented the only clinical practical innovation for lung NET patients over the last years. Therefore, for lung NETs, a multidisciplinary discussion within a dedicated team remains critical for an adequate decision-making. Although the main regulatory authorities considered the everolimus-related evidence is enough to approve the drug in advanced lung NETs, several clinical features deserve to be discussed. In this review, we systemically and critically analysed the main clinical studies including patients with advanced lung NETs receiving everolimus. Furthermore, we reported the biological and clinical background of everolimus in lung NET setting. The purpose of this review is to help clinical community to contextualize evidence and experience for a personalised use of this drug in clinical practice in the context of advanced lung NET patients.

p110δ PI3K as a therapeutic target of solid tumours

From the time of first characterization of PI3K as a heterodimer made up of a p110 catalytic subunit and a regulatory subunit, a wealth of evidence have placed the class IA PI3Ks at the forefront of drug development for the treatment of various diseases including cancer. The p110α isoform was quickly brought at the centre of attention in the field of cancer research by the discovery of cancer-specific gain-of-function mutations in PIK3CA gene in a range of human solid tumours. In contrast, p110δ PI3K was placed into the spotlight of immunity, inflammation and haematologic malignancies because of the preferential expression of this isoform in leucocytes and the rare mutations in PIK3CD gene. The last decade, however, several studies have provided evidence showing that the correlation between the PIK3CA mutations and the response to PI3K inhibition is less clear than originally considered, whereas concurrently an unexpected role of p110δ PI3K in solid tumours has being emerging. While PIK3CD is mostly non-mutated in cancer, the expression levels of p110δ protein seem to act as an intrinsic cancer-causing driver in various solid tumours including breast, prostate, colorectal and liver cancer, Merkel-Cell carcinoma, glioblastoma and neurobalstoma. Furthermore, p110δ selective inhibitors are being studied as potential single agent treatments or as combination partners in attempt to improve cancer immunotherapy, with both strategies to shown great promise for the treatment of several solid tumours. In this review, we discuss the evidence implicating the p110δ PI3K in human solid tumours, their impact on the current state of the field and the potential of using p110δ-selective inhibitors as monotherapy or combined therapy in different cancer contexts.

Identification of the Mutational Landscape of Gynecological Malignancies

Background: Cancer is a complex disease that arises from the accumulation of multiple genetic and non-genetic changes. Advances in sequencing technologies have allowed unbiased and global analysis of patient-derived tumor samples and the discovery of genetic and transcriptional changes in key genes and oncogenic pathways. That in turn has facilitated a better understanding of the underlying causes of cancer initiation and progression, resulting in new therapeutic targets. Methods: In our study, we have analyzed the mutational landscape of gynecological malignancies using datasets from The Cancer Genome Atlas (TCGA). We have also analyzed Oncomine datasets to establish the impact of their alteration on disease recurrence and survival of patients. Results: In this study, we analyzed a series of different gynecological malignancies for commonly occurring genetic and non-genetic alterations. These studies show that white women have higher incidence of gynecological malignancies. Furthermore, our study identified 16 genes that are altered at a frequency >10% among all of the gynecological malignancies and tumor suppressor TP53 is the most altered gene in these malignancies (>50% of the cases). The top 16 genes fall into the categories of either tumor suppressor or oncogenes and a subset of these genes are associated with poor prognosis, some affecting recurrence and survival of ovarian cancer patients. Conclusion: In sum, our study identified 16 major genes that are broadly mutated in a large majority of gynecological malignancies and in some cases predict survival and recurrence in patients with gynecological malignancies. We predict that the functional studies will determine their relative role in the initiation and progression of gynecological malignancies and also establish if some of them represents drug targets for anti-cancer therapy.

mTOR Pathway in Gastroenteropancreatic Neuroendocrine Tumor (GEP-NETs)

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) originate from neuroendocrine cells in the gastrointestinal tract. They are heterogeneous, and though initially considered rare tumors, the incidence of GEP-NENs has increased in the last few decades. Therapeutic approaches for the metastatic disease include surgery, radiological intervention by chemoembolisation, radiofrequency ablation, biological therapy in addition to somatostatin analogs, and PRRT therapy (177Lu-DOTATATE). The PI3K-AKT-mTOR pathway is essential in the regulation of protein translation, cell growth, and metabolism. Evidence suggests that the mTOR pathway is involved in malignant progression and resistance to treatment through over-activation of several mechanisms. PI3K, one of the main downstream of the Akt-mTOR axis, is mainly involved in the neoplastic process. This pathway is frequently deregulated in human tumors, making it a central target in the development of new anti-cancer treatments. Recent molecular studies identify potential targets within the PI3K/Akt/mTOR pathway in GEP-NENs. However, the use of target therapy has been known to lead to resistance due to several mechanisms such as feedback activation of alternative pathways, inactivation of protein kinases, and deregulation of the downstream mTOR components. Therefore, the specific role of targeted drugs for the management of GEP-NENs is yet to be well-defined. The variable clinical presentation of advanced neuroendocrine tumors is a significant challenge for designing studies. This review aims to highlight the role of the PI3K/Akt/mTOR pathway in the development of neuroendocrine tumors and further specify its potential as a therapeutic target in advanced stages.

Discovery of an AKT Degrader with Prolonged Inhibition of Downstream Signaling

The PI3K/AKT signaling cascade is one of the most commonly dysregulated pathways in cancer, with over half of tumors exhibiting aberrant AKT activation. Although potent small-molecule AKT inhibitors have entered clinical trials, robust and durable therapeutic responses have not been observed. As an alternative strategy to target AKT, we report the development of INY-03-041, a pan-AKT degrader consisting of the ATP-competitive AKT inhibitor GDC-0068 conjugated to lenalidomide, a recruiter of the E3 ubiquitin ligase substrate adaptor Cereblon (CRBN). INY-03-041 induced potent degradation of all three AKT isoforms and displayed enhanced anti-proliferative effects relative to GDC-0068. Notably, INY-03-041 promoted sustained AKT degradation and inhibition of downstream signaling effects for up to 96 h, even after compound washout. Our findings suggest that AKT degradation may confer prolonged pharmacological effects compared with inhibition, and highlight the potential advantages of AKT-targeted degradation.

A Phase IIa Trial of Metformin for Colorectal Cancer Risk Reduction among Individuals with History of Colorectal Adenomas and Elevated Body Mass Index

Obesity is associated with risk of colorectal adenoma (CRA) and colorectal cancer. The signaling pathway activated by metformin (LKB1/AMPK/mTOR) is implicated in tumor suppression in Apc^Min/+ mice via metformin-induced reduction in polyp burden, increased ratio of pAMPK/AMPK, decreased pmTOR/mTOR ratio, and decreased pS6^Ser235/S6^Ser235 ratio in polyps. We hypothesized that metformin would affect colorectal tissue S6^Ser235 among obese patients with recent history of CRA. A phase IIa clinical biomarker trial was conducted via the U.S. National Cancer Institute-Chemoprevention Consortium. Nondiabetic, obese subjects (BMI ≥30) ages 35 to 80 with recent history of CRA were included. Subjects received 12 weeks of oral metformin 1,000 mg twice every day. Rectal mucosa biopsies were obtained at baseline and end-of-treatment (EOT) endoscopy. Tissue S6^Ser235 and Ki-67 immunostaining were analyzed in a blinded fashion using Histo score (Hscore) analysis. Among 32 eligible subjects, the mean baseline BMI was 34.9. Comparing EOT to baseline tissue S6^Ser235 by IHC, no significant differences were observed. Mean (SD) Hscore at baseline was 1.1 (0.57) and 1.1 (0.51) at EOT; median Hscore change was 0.034 (P = 0.77). Similarly, Ki-67 levels were unaffected by the intervention. The adverse events were consistent with metformin's known side-effect profile. Among obese patients with CRA, 12 weeks of oral metformin does not reduce rectal mucosa pS6 or Ki-67 levels. Further research is needed to determine what effects metformin has on the target tissue of origin as metformin continues to be pursued as a colorectal cancer chemopreventive agent.

Catalpol induces cell activity to promote axonal regeneration via the PI3K/AKT/mTOR pathway in vivo and in vitro stroke model

Background

To investigate the role and mechanism of catalpol on neuronal cell activity to promote axonal regeneration via PI3K/AKT/mTOR pathway after stroke.

Methods

In vivo the effect of catalpol (2.5, 5, 7.5 mg/kg; i.p) or vehicle administered 24 h after stroke and then daily for 7 days on behavior, Map-2⁺/p-S6⁺ and Map-2⁺/GAP-43⁺ immunofluorescence were assessed in a rat model of stroke. Then in vitro, an oxygen-glucose deprivation (OGD/R) model was established to observe the effect of catalpol (0.1, 1, 10 and 100 µg·mL^-1) on cultural neurons survive rate, neuronal cell activity and axon growth. Moreover, rapamycin (Rapa) was used to inhibit the mTOR pathway to observe the catalpol mechanism on neuronal cell activity to promote axonal growth, and the proteins related with PI3K/AKT/mTOR pathway were detected by Western blot assay.

Results

Repeated treatments with catalpol improved neurological score and significantly enhanced neuronal cell activity, then promote axonal regeneration after stroke. While in vitro, catalpol also increased the survive rate and axonal growth of the neurons. Catalpol can reversed the Rapa inhibited effects on neurons' survive and axon extending. Catalpol can also reversed proteins reduced by Rapa related with PI3K/AKT/mTOR pathway.

Conclusions

These results suggested that catalpol might contribute to internal neuronal cell activity and axonal regeneration by regulating PI3K/AKT/mTOR pathway.

Clinical applications of (epi)genetics in gastroenteropancreatic neuroendocrine neoplasms: Moving towards liquid biopsies

High-throughput analysis, including next-generation sequencing and microarrays, have strongly improved our understanding of cancer biology. However, genomic data on rare cancer types, such as neuroendocrine neoplasms, has been lagging behind. Neuroendocrine neoplasms (NENs) develop from endocrine cells spread throughout the body and are highly heterogeneous in biological behavior. In this challenging disease, there is an urgent need for new therapies and new diagnostic, prognostic, follow-up and predictive biomarkers to aid patient management. The last decade, molecular data on neuroendocrine neoplasms of the gastrointestinal tract and pancreas, termed gastroenteropancreatic NENs (GEP-NENs), has strongly expanded. The aim of this review is to give an overview of the recent advances on (epi)genetic level and highlight their clinical applications to address the current needs in GEP-NENs. We illustrate how molecular alterations can be and are being used as therapeutic targets, how mutations in DAXX/ATRX and copy number variations could be used as prognostic biomarkers, how far we are in identifying predictive biomarkers and how genetics can contribute to GEP-NEN classification. Finally, we discuss recent studies on liquid biopsies in the field of GEP-NENs and illustrate how liquid biopsies can play a role in patient management. In conclusion, molecular studies have suggested multiple potential biomarkers, but further validation is ongoing.

Contactin 1 modulates pegylated arginase resistance in small cell lung cancer through induction of epithelial-mesenchymal transition

Drug resistance is a major hurdle in the treatment of small cell lung cancer (SCLC). Previously we demonstrated the potential anticancer effect of pegylated arginase BCT-100 in SCLC cell lines and xenograft models. To facilitate future clinical application of BCT-100 in SCLC treatment, we elucidated the potential mechanisms that underlie acquired drug resistance to BCT-100. H446 and H526 SCLC cells were serially cultured in stepwise increasing concentrations of BCT-100 until stable BCT-100-resistant cell lines emerged (H446-BR and H526-BR). Compared with parent cells, H446-BR and H526-BR displayed stronger migration ability, anoikis resistance and EMT progression. Gene chip assay was employed to select three potential targets (CDH17, CNTN-1 and IGF2BP1). Silencing CNTN-1 rather than CDH17 or IGF2BP1 in H446-BR and H526-BR cells re-sensitized resistant cells to BCT-100 treatment and attenuated the epithelial–mesenchymal transition (EMT) phenotype. The AKT signaling pathway was activated in H446-BR and H526-BR cells accompanied by EMT progression, and AKT inhibitor LY294002 reversed the EMT progression in resistant cells.

mTOR: Role in cancer, metastasis and drug resistance

Mammalian target of rapamycin (mTOR) is a serine/threonine kinase that gets inputs from the amino acids, nutrients, growth factor, and environmental cues to regulate varieties of fundamental cellular processes which include protein synthesis, growth, metabolism, aging, regeneration, autophagy, etc. The mTOR is frequently deregulated in human cancer and activating somatic mutations of mTOR were recently identified in several types of human cancer and hence mTOR is therapeutically targeted. mTOR inhibitors were commonly used as immunosuppressors and currently, it is approved for the treatment of human malignancies. This review briefly focuses on the structure and biological functions of mTOR. It extensively discusses the genetic deregulation of mTOR including amplifications and somatic mutations, mTOR-mediated cell growth promoting signaling, therapeutic targeting of mTOR and the mechanisms of resistance, the role of mTOR in precision medicine and other recent advances in further understanding the role of mTOR in cancer.

Positive Effects of PI3K/Akt Signaling Inhibition on PTEN and P53 in Prevention of Acute Lymphoblastic Leukemia Tumor Cells

Purpose: The PI3K/Akt signaling pathway regulates cell growth, proliferation and viability in hematopoietic cells. This pathway always dysregulates in acute lymphoblastic leukemia (ALL). PTEN and P53 are tumor suppressor genes correlated with PI3K/Akt signaling pathway, and both have a tight link in regulation of cell proliferation and cell death. In this study, we investigated the effects of dual targeting of PI3K/Akt pathway by combined inhibition with nvp-BKM-120 (PI3K inhibitor) and MK-2206 (Akt inhibitor) in relation with PTEN and P53 on apoptosis and proliferation of leukemia cells.

Methods: Both T and B ALL cell lines were treated with both inhibitors alone or in combination with each other, and induction of apoptosis and inhibition of proliferation were evaluated by flow cytometry. Expression levels of PTEN as well as p53 mRNA and protein were measured by real-time qRT-PCR and western blot, respectively.

Results: We indicated that both inhibitors (BKM-120 and MK-2206) decreased cell viability and increased cytotoxicity in leukemia cells. Reduction in Akt phosphorylation increased PTEN and p53 mRNA and p53 protein level (in PTEN positive versus PTEN negative cell lines). Additionally, both inhibitors, particularly in combination with each other, increased apoptosis (evaluated with Annexin V and caspase 3) and reduced proliferation (Ki67 expression) in leukemia cells. However, administration of IL7 downregulated PTEN and P53 mRNA expression and rescued cancer cells following inhibition of BKM-120 and MK-2206.

Conclusion: This investigation suggested that inhibition of Akt and PI3K could be helpful in leukemia treatment.

Targeting mTOR for cancer therapy

Mechanistic target of rapamycin (mTOR) is a protein kinase regulating cell growth, survival, metabolism, and immunity. mTOR is usually assembled into several complexes such as mTOR complex 1/2 (mTORC1/2). In cooperation with raptor, rictor, LST8, and mSin1, key components in mTORC1 or mTORC2, mTOR catalyzes the phosphorylation of multiple targets such as ribosomal protein S6 kinase β-1 (S6K1), eukaryotic translation initiation factor 4E binding protein 1 (4E-BP1), Akt, protein kinase C (PKC), and type-I insulin-like growth factor receptor (IGF-IR), thereby regulating protein synthesis, nutrients metabolism, growth factor signaling, cell growth, and migration. Activation of mTOR promotes tumor growth and metastasis. Many mTOR inhibitors have been developed to treat cancer. While some of the mTOR inhibitors have been approved to treat human cancer, more mTOR inhibitors are being evaluated in clinical trials. Here, we update recent advances in exploring mTOR signaling and the development of mTOR inhibitors for cancer therapy. In addition, we discuss the mechanisms underlying the resistance to mTOR inhibitors in cancer cells.

Anti-tumour activity of everolimus and sunitinib in neuroendocrine neoplasms

Comparisons between everolimus and sunitinib regarding their efficacy and safety in neuroendocrine neoplasms (NENs) are scarce. We retrospectively analysed the clinicopathological characteristics and outcomes in 92 patients with well-differentiated (WD) NEN of different origin (57 pancreatic NENs (PanNENs)), treated with molecular targeted therapy (MTT) with everolimus or sunitinib, first- (73:19) or second-line (sequential; 12:22) for progressive disease. Disease control rates (DCR: partial response or stable disease) at first-line were higher in all patients treated with everolimus than sunitinib (64/73 vs 12/19, P = 0.012). In PanNENs, DCR at first-line everolimus was 36/42 versus 9/15 with sunitinib (P = 0.062). Progression-free survival (PFS) at first-line everolimus was longer than sunitinib (31 months (95% CI: 23.1-38.9) vs 9 months (95% CI: 0-18.5); log-rank P < 0.0001) in the whole cohort and the subset of PanNENs (log-rank P < 0.0001). Median PFS at second-line MTT was 12 months with everolimus (95% CI: 4.1-19.9) vs 13 months with sunitinib (95% CI: 9.3-16.7; log-rank P = 0.951). Treatment with sunitinib (HR: 3.47; 95% CI: 1.5-8.3; P value: 0.005), KI67 >20% (HR: 6.38; 95% CI: 1.3-31.3; P = 0.022) and prior chemotherapy (HR: 2.71; 95% CI: 1.2-6.3; P = 0.021) were negative predictors for PFS at first line in multivariable and also confirmed at multi-state modelling analyses. Side effect (SE) analysis indicated events of serious toxicities (Grades 3 and 4: n = 13/85 for everolimus and n = 4/41 for sunitinib). Discontinuation rate due to SEs was 20/85 for everolimus versus 4/41 for sunitinib (P = 0.065). No additive toxicity of second-line MTT was confirmed. Based on these findings, and until reliable predictors of response become available, everolimus may be preferable to sunitinib when initiating MTT in progressive NENs.

mTOR Signaling in Cancer and mTOR Inhibitors in Solid Tumor Targeting Therapy

The mammalian or mechanistic target of rapamycin (mTOR) pathway plays a crucial role in regulation of cell survival, metabolism, growth and protein synthesis in response to upstream signals in both normal physiological and pathological conditions, especially in cancer. Aberrant mTOR signaling resulting from genetic alterations from different levels of the signal cascade is commonly observed in various types of cancers. Upon hyperactivation, mTOR signaling promotes cell proliferation and metabolism that contribute to tumor initiation and progression. In addition, mTOR also negatively regulates autophagy via different ways. We discuss mTOR signaling and its key upstream and downstream factors, the specific genetic changes in the mTOR pathway and the inhibitors of mTOR applied as therapeutic strategies in eight solid tumors. Although monotherapy and combination therapy with mTOR inhibitors have been extensively applied in preclinical and clinical trials in various cancer types, innovative therapies with better efficacy and less drug resistance are still in great need, and new biomarkers and deep sequencing technologies will facilitate these mTOR targeting drugs benefit the cancer patients in personalized therapy.

Efficacy and Safety of Everolimus plus Somatostatin Analogues in Patients with Neuroendocrine Tumors

Everolimus, an oral mammalian target of rapamycin(mTOR) inhibitor, which acts upstream of the phosphoinositide 3-kinase/protein kinase B(PI3K/AKT) signaling pathway to downregulate cellular metabolism, growth, proliferation, and angiogenesis, has been shown to significantly prolong the progression-free survival of patients with advanced neuroendocrine tumors. Somatostatin analogues (SSAs) such as octreotide, lanreotide, and pasireotide, have been widely used for symptom control and antiproliferative effects in metastatic or unresectable neuroendocrine tumors. Both everolimus and SSAs have demonstrated antitumor effects in randomized controlled trials (RCTs) involving selected patients with neuroendocrine tumors, but the efficacy and safety of their combined use require further investigation. In this systematic review, we summarize the published studies that have investigated the use of everolimus and SSAs to provide a comprehensive understanding of their combined effects and better guidance for the treatment of neuroendocrine tumors.

A Patient-derived Xenograft Model of Pancreatic Neuroendocrine Tumors Identifies Sapanisertib as a Possible New Treatment for Everolimus-resistant Tumors

Patients with pancreatic neuroendocrine tumors (PNET) commonly develop advanced disease and require systemic therapy. However, treatment options remain limited, in part, because experimental models that reliably emulate PNET disease are lacking. We therefore developed a patient-derived xenograft model of PNET (PDX-PNET), which we then used to evaluate two mTOR inhibitor drugs: FDA-approved everolimus and the investigational new drug sapanisertib. PDX-PNETs maintained a PNET morphology and PNET-specific gene expression signature with serial passage. PDX-PNETs also harbored mutations in genes previously associated with PNETs (such as MEN1 and PTEN), displayed activation of the mTOR pathway, and could be detected by Gallium-68 DOTATATE PET-CT. Treatment of PDX-PNETs with either everolimus or sapanisertib strongly inhibited growth. As seen in patients, some PDX-PNETs developed resistance to everolimus. However, sapanisertib, a more potent inhibitor of the mTOR pathway, caused tumor shrinkage in most everolimus-resistant tumors. Our PDX-PNET model is the first available, validated PDX model for PNET, and preclinical data from the use of this model suggest that sapanisertib may be an effective new treatment option for patients with PNET or everolimus-resistant PNET.

What's New in Gastric Cancer: The Therapeutic Implications of Molecular Classifications and Future Perspectives

Despite some remarkable innovations and the advent of novel molecular classifications the prognosis of patients with advanced gastric cancer (GC) remains overall poor and current clinical application of new advances is disappointing. During the last years only Trastuzumab and Ramucirumab have been approved and currently used as standard of care targeted therapies, but the systemic management of advanced disease did not radically change in contrast with the high number of molecular drivers identified. The Cancer Genome Atlas (TCGA) and Asian Cancer Research Group (ACRG) classifications paved the way, also for GC, to that more contemporary therapeutic approach called "precision medicine" even if tumor heterogeneity and a complex genetic landscape still represent a strong barrier. The identification of specific cancer subgroups is also making possible a better selection of patients that are most likely to respond to immunotherapy. This review aims to critically overview the available molecular classifications summarizing the main druggable molecular drivers and their possible therapeutic implications also taking advantage of new technologies and acquisitions.

Molecular Genetic Studies of Pancreatic Neuroendocrine Tumors: New Therapeutic Approaches

Pancreatic neuroendocrine tumors (PNETs) arise sporadically or as part of familial syndromes. Genetic studies of hereditary syndromes and whole exome sequencing analysis of sporadic NETs have revealed the roles of some genes involved in PNET tumorigenesis. The multiple endocrine neoplasia type 1 (MEN1) gene is most commonly mutated. Its encoded protein, menin, has roles in transcriptional regulation, genome stability, DNA repair, protein degradation, cell motility and adhesion, microRNA biogenesis, cell division, cell cycle control, and epigenetic regulation. Therapies targeting epigenetic regulation and MEN1 gene replacement have been reported to be effective in preclinical models.

Predictive Markers of Response to Everolimus and Sunitinib in Neuroendocrine Tumors

Neuroendocrine tumors (NETs) represent a large and heterogeneous group of malignancies with various biological and clinical characteristics, depending on the site of origin and the grade of tumor proliferation. In NETs, as in other cancer types, molecularly targeted therapies have radically changed the therapeutic landscape. Recently two targeted agents, the mammalian target of rapamycin inhibitor everolimus and the tyrosine kinase inhibitor sunitinib, have both demonstrated significantly prolonged progression free survival in patients with advanced pancreatic NETs. Despite these important therapeutic developments, there are still significant limitations to the use of these agents due to the lack of accurate biomarkers for predicting tumor response and efficacy of therapy. In this review, we provide an overview of the current clinical data for the evaluation of predictive factors of response to/efficacy of everolimus and sunitinib in advanced pancreatic NETs. Surrogate indicators discussed include circulating and tissue markers, as well as non-invasive imaging techniques.

Radio-sensitizing effects of VE-821 and beyond: Distinct phosphoproteomic and metabolomic changes after ATR inhibition in irradiated MOLT-4 cells

Current anti-cancer strategy takes advantage of tumour specific abnormalities in DNA damage response to radio- or chemo-therapy. Inhibition of the ATR/Chk1 pathway has been shown to be synthetically lethal in cells with high levels of oncogene-induced replication stress and in p53- or ATM- deficient cells. In the presented study, we aimed to elucidate molecular mechanisms underlying radiosensitization of T-lymphocyte leukemic MOLT-4 cells by VE-821, a higly potent and specific inhibitor of ATR. We combined multiple approaches: cell biology techniques to reveal the inhibitor-induced phenotypes, and quantitative proteomics, phosphoproteomics, and metabolomics to comprehensively describe drug-induced changes in irradiated cells. VE-821 radiosensitized MOLT-4 cells, and furthermore 10 μM VE-821 significantly affected proliferation of sham-irradiated MOLT-4 cells. We detected 623 differentially regulated phosphorylation sites. We revealed changes not only in DDR-related pathways and kinases, but also in pathways and kinases involved in maintaining cellular metabolism. Notably, we found downregulation of mTOR, the main regulator of cellular metabolism, which was most likely caused by an off-target effect of the inhibitor, and we propose that mTOR inhibition could be one of the factors contributing to the phenotype observed after treating MOLT-4 cells with 10 μM VE-821. In the metabolomic analysis, 206 intermediary metabolites were detected. The data indicated that VE-821 potentiated metabolic disruption induced by irradiation and affected the response to irradiation-induced oxidative stress. Upon irradiation, recovery of damaged deoxynucleotides might be affected by VE-821, hampering DNA repair by their deficiency. Taken together, this is the first study describing a complex scenario of cellular events that might be ATR-dependent or triggered by ATR inhibition in irradiated MOLT-4 cells. Data are available via ProteomeXchange with identifier PXD008925.

Everolimus in the treatment of neuroendocrine tumors: efficacy, side-effects, resistance, and factors affecting its place in the treatment sequence

INTRODUCTION

Since the initial approval of everolimus in 2011, there have been a number of important changes in therapeutic/diagnostic modalities as well as classification/staging systems of neuroendocrine tumors (NETs), which can significantly impact the use of everolimus in patients with advanced NETs. Areas covered: The efficacy of everolimus monotherapy and combination therapy demonstrated in clinical studies involving patients with advanced NETs are reviewed. Several factors affecting everolimus use are described including: the development and routine use of NET classification/staging systems; widespread use of molecular imaging modalities; side effects; drug resistance; and the availability of other treatment options. Furthermore, the current position of everolimus in the treatment approach is discussed, taking into account the recommendations from the recent guidelines. Expert opinion: Although everolimus demonstrated its high efficacy and tolerability in the RADIANT trials and other clinical studies, there still remain a number of controversies related to everolimus treatment in the management of NETs. The synergistic anti-growth effect of other agents in combination with everolimus or its effect on overall survival have not been established. The appropriate order of the use of everolimus in the treatment of advanced NETs still remains unclear, which needs to be defined in further studies and will be addressed in the new guidelines.