Nutrient restriction-activated Fra-2 promotes tumor progression via IGF1R in miR-15a downmodulated pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a lethal disease, characterized by an intense desmoplastic reaction that compresses blood vessels and limits nutrient supplies. PDAC aggressiveness largely relies on its extraordinary capability to thrive and progress in a challenging tumor microenvironment. Dysregulation of the onco-suppressor miR-15a has been extensively documented in PDAC. Here, we identified the transcription factor Fos-related antigen-2 (Fra-2) as a miR-15a target mediating the adaptive mechanism of PDAC to nutrient deprivation. We report that the IGF1 signaling pathway was enhanced in nutrient deprived PDAC cells and that Fra-2 and IGF1R were significantly overexpressed in miR-15a downmodulated PDAC patients. Mechanistically, we discovered that miR-15a repressed IGF1R expression via Fra-2 targeting. In miR-15a-low context, IGF1R hyperactivated mTOR, modulated the autophagic flux and sustained PDAC growth in nutrient deprivation. In a genetic mouse model, Mir15aKO PDAC showed Fra-2 and Igf1r upregulation and mTOR activation in response to diet restriction. Consistently, nutrient restriction improved the efficacy of IGF1R inhibition in a Fra-2 dependent manner. Overall, our results point to a crucial role of Fra-2 in the cellular stress response due to nutrient restriction typical of pancreatic cancer and support IGF1R as a promising and vulnerable target in miR-15a downmodulated PDAC.

Role of Fra-2 in cancer

Fos-related antigen-2 (Fra-2) is the most recently discovered member of the Fos family and, by dimerizing with Jun proteins, forms the activator protein 1 (AP-1) transcription factor. By inducing or repressing the transcription of several target genes, Fra-2 is critically involved in the modulation of cell response to a variety of extracellular stimuli, stressors and intracellular changes. In physiological conditions, Fra-2 has been found to be ubiquitously expressed in human cells, regulating differentiation and homeostasis of bone, muscle, nervous, lymphoid and other tissues. While other AP-1 members, like Jun and Fos, are well characterized, studies of Fra-2 functions in cancer are still at an early stage. Due to the lack of a trans-activating domain, which is present in other Fos proteins, it has been suggested that Fra-2 might inhibit cell transformation, eventually exerting an anti-tumor effect. In human malignancies, however, Fra-2 activity is enhanced (or induced) by dysregulation of microRNAs, oncogenes and extracellular signaling, suggesting a multifaceted role. Therefore, Fra-2 can promote or prevent transformation, proliferation, migration, epithelial-mesenchymal transition, drug resistance and metastasis formation in a tumor- and context-dependent manner. Intriguingly, recent data reports that Fra-2 is also expressed in cancer associated cells, contributing to the intricate crosstalk between neoplastic and non-neoplastic cells, that leads to the evolution and remodeling of the tumor microenvironment. In this review we summarize three decades of research on Fra-2, focusing on its oncogenic and anti-oncogenic effects in tumor progression and dissemination.

Complete miRNA-15/16 loss in mice promotes hematopoietic progenitor expansion and a myeloid-biased hyperproliferative state

Dysregulated apoptosis and proliferation are fundamental properties of cancer, and microRNAs (miRNA) are critical regulators of these processes. Loss of miR-15a/16-1 at chromosome 13q14 is the most common genomic aberration in chronic lymphocytic leukemia (CLL). Correspondingly, the deletion of either murine miR-15a/16-1 or miR-15b/16-2 locus in mice is linked to B cell lymphoproliferative malignancies. However, unexpectedly, when both miR-15/16 clusters are eliminated, most double knockout (DKO) mice develop acute myeloid leukemia (AML). Moreover, in patients with CLL, significantly reduced expression of miR-15a, miR-15b, and miR-16 associates with progression of myelodysplastic syndrome to AML, as well as blast crisis in chronic myeloid leukemia. Thus, the miR-15/16 clusters have a biological relevance for myeloid neoplasms. Here, we demonstrate that the myeloproliferative phenotype in DKO mice correlates with an increase of hematopoietic stem and progenitor cells (HSPC) early in life. Using single-cell transcriptomic analyses, we presented the molecular underpinning of increased myeloid output in the HSPC of DKO mice with gene signatures suggestive of dysregulated hematopoiesis, metabolic activities, and cell cycle stages. Functionally, we found that multipotent progenitors (MPP) of DKO mice have increased self-renewing capacities and give rise to significantly more progeny in the granulocytic compartment. Moreover, a unique transcriptomic signature of DKO MPP correlates with poor outcome in patients with AML. Together, these data point to a unique regulatory role for miR-15/16 during the early stages of hematopoiesis and to a potentially useful biomarker for the pathogenesis of myeloid neoplasms.

A-to-I edited miR-411-5p targets MET and promotes TKI response in NSCLC-resistant cells

Non-small cell lung cancer (NSCLC) patients carrying an epidermal growth factor receptor (EGFR) mutation have an initial favorable clinical response to the tyrosine kinase inhibitors (TKIs). Unfortunately, rapid resistance occurs mainly because of genetic alterations, including amplification of the hepatocyte growth factor receptor (MET) and its abnormal activity. The RNA post-transcriptional modifications that contribute to aberrant expression of MET in cancer are largely under-investigated and among them is the adenosine-to-inosine (A-to-I) RNA editing of microRNAs. A reduction of A-to-I editing in position 5 of miR-411-5p has been identified in several cancers, including NSCLC. In this study, thanks to cancer-associated gene expression analysis, we assessed the effect of the edited miR-411-5p on NSCLC cell lines. We found that edited miR-411-5p directly targets MET and negatively affects the mitogen-activated protein kinases (MAPKs) pathway. Considering the predominant role of the MAPKs pathway on TKIs resistance, we generated NSCLC EGFR mutated cell lines resistant to TK inhibitors and evaluated the effect of edited miR-411-5p overexpression. We found that the edited miR-411-5p reduces proliferation and induces apoptosis, promoting EGFR TKIs response in NSCLC-resistant cells.

Abstract 4823: The novel miR-15a/Fra-2/IGF1R axis drives response to starvation-induced cell stress in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a relatively uncommon malignancy; however, its incidence is rising worldwide, and it is expected to become the second-leading cause of cancer-related death by 2030. From a histological point of view, PDAC is characterized by a prominent desmoplastic reaction that compresses blood vessels, limiting oxygen and nutrient availability in the tumor microenvironment. Despite that, PDAC cells are capable to adapt dynamically to these stress conditions, adopting different strategies that includes the strict regulation of the autophagic flux. Thus, studying these adaptive mechanisms is crucial to understand PDAC progression and to establish new therapeutic modalities to tackle it. Here, we explore the role of the tumor suppressor miR-15a in the regulation of its putative target Fra-2, a transcription factor, commonly activated by cell stress. By employing IPA on PDAC tumors from TCGA dataset, we found that both miR-15a and its target Fra-2 are predicted to regulate the IGF-1 signaling pathway. In an independent cohort of 44 PDAC samples, miR-15a levels inversely correlated with both Fra-2 and IGF1R expression; conversely, Fra-2 significantly correlated with IGF1R. By chromatin immunoprecipitation and luciferase assay, we assessed that miR-15a directly targeted Fra-2 and IGF1R that, in turn, is transcriptionally regulated by Fra-2 activity. Then, we investigated the role of miR-15a/Fra-2 regulation of IGF1R in the response to starvation-induced cell stress. In starved PDAC cell lines, Fra-2 transcriptional activity triggered IGF1R promoter, causing IGF1R overexpression in control cells but not in miR-15a-overexpressing cells. Consistently, the IGF1 release after starvation induced phosphorylation of IGF1R and activation of the downstream mTOR pathway in control cells but not in miR-15a-overexpressing cells. Therefore, TEM and western blot analysis demonstrated that activation of mTOR via IGF1 release reduced the autophagic flux of PDAC control cell lines compared to miR-15a overexpressing cells under starvation. To assess our results in vivo, we injected PDAC cells wild type or Fra-2 knockout into the flank of nude mice. At tumor onset, mice were randomly divided in two groups and fed with control or hypoproteic diet for three weeks. Hypoproteic diet did not interfere with the growth of wild-type tumors, by contrast, significantly impaired Fra-2KO tumors growth rate. Tumor analysis revealed that hypoproteic diet potently induced IGF1R overexpression and mTOR pathway activation in wild-type tumors but not in Fra-2KO tumors. Our findings demonstrate that IGF1R expression is regulated by miR-15a directly and indirectly via Fra-2 in PDAC. This novel miR-15a/Fra-2/IGF1R axis, triggered by starvation, regulates the autophagic flux and growth of PDAC cells in stress condition, and could be targeted by specific small inhibitors.

Citation Format: Gian Luca Rampioni Vinciguerra, Marina Capece, Luca Reggiani Bonetti, Paolo Magistri, Federica Calore, Giovanni Nigita, Rosario Distefano, Roberto Ballarin, Fabrizio Di Benedetto, Andrea Vecchione, Barbara Belletti, Gustavo Baldassarre, Francesca Lovat, Carlo M. Croce. The novel miR-15a/Fra-2/IGF1R axis drives response to starvation-induced cell stress in pancreatic ductal adenocarcinoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4823.

Abstract 3903: Role of the miR-301a/Fra-2/GLIPR1 axis in lung cancer cisplatin resistance

Lung cancer is the leading cause of cancer-related mortality in both men and women worldwide. Despite the administration of platinum compounds represents the main treatment, the majority of tumors remains intrinsically resistant. In lung cancer, miR-301a exerts a main role by modulating the activity of transcription factors like NF-kB and Stat3. Here, we dissected the contribution of miR-301a in the regulation of its new identified target Fos-related antigen-2 (Fra-2), a transcription factor that belongs to the Fos/AP-1 family. By microarray analysis, we discovered that Fra-2 overexpression increased glioma pathogenesis-related protein 1 (GLIPR1) levels, a mediator of cisplatin resistance in lung cancer. Its mechanism of regulation is still unclear. We demonstrated that GLIPR1 is also a miR-301a target. In vitro, modulation of miR-301a reduced Fra-2 and GLIPR1 levels; conversely, Fra-2 overexpression significantly increased GLIPR1 and miR-301a. Then, by chromatin immunoprecipitation assay, we confirmed that Fra-2 interacts with the promoter regions of both GLIPR1 and MIR301A genes, supporting that miR-301a/Fra-2/GLIPR1 axis could be autoregulated by feedback loop in which Fra-2 promotes the transcription of MIR301A gene. Investigating the effect of this new axis on the response to cisplatin, we observed that both Fra-2/GLIPR1 overexpression and miR-301a silencing induced cisplatin resistance in lung cancer cells. By contrast, silencing of GLIPR1 and combined administration of low doses of Fos/AP-1 inhibitor restored the cisplatin sensitivity in Fra-2 overexpressing cells. In the lung adenocarcinoma samples from the TCGA dataset, miR-301a overexpression inversely correlated with Fra-2 and GLIPR1 expression. Consistently, the overexpression of miR-301a identified a fraction of tumors with low expression of Fra-2 and GLIPR1 in an internal cohort of lung cancer samples. Altogether, our findings identify the miR-301a/Fra-2/GLIPR1 axis that contributes to cisplatin resistance in lung cancer cells and could serve as biomarker to stratify patients who may benefit from cisplatin administration, alone or in combination with Fos/AP-1 inhibitors.

Citation Format: Francesca Lovat, Gian Luca Rampioni Vinciguerra, Marina Capece, Rosario Distefano, Giovanni Nigita, Andrea Vecchione, Carlo M. Croce. Role of the miR-301a/Fra-2/GLIPR1 axis in lung cancer cisplatin resistance. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3903.

The TLR7/8/9 Antagonist IMO-8503 Inhibits Cancer-Induced Cachexia

: Muscle wasting is a feature of the cachexia syndrome, which contributes significantly to the mortality of patients with cancer. We have previously demonstrated that miR-21 is secreted through extracellular vesicles (EV) by lung and pancreatic cancer cells and promotes JNK-dependent cell death through its binding to the TLR7 receptor in murine myoblasts. Here, we evaluate the ability of IMO-8503, a TLR7, 8, and 9 antagonist, to inhibit cancer-induced cachexia. Using EVs isolated from lung and pancreatic cancer cells and from patient plasma samples, we demonstrate that IMO-8503 inhibits cell death induced by circulating miRNAs with no significant toxicity. Intraperitoneal administration of the antagonist in a murine model for Lewis lung carcinoma (LLC-induced cachexia) strongly impaired several cachexia-related features, such as the expression of Pax7 as well as caspase-3 and PARP cleavage in skeletal muscles, and significantly prevented the loss of lean mass in tumor-bearing mice. IMO-8503 also impaired circulating miRNA-induced cell death in human primary myoblasts. Taken together, our findings strongly indicate that IMO-8503 serves as a potential therapy for the treatment of cancer cachexia. SIGNIFICANCE: Cancer-associated cachexia is a significant problem for patients with cancer that remain poorly understood, understudied, and inadequately treated; these findings report a potential new therapeutic for the treatment of TLR7-mediated cancer cachexia.

Lung cancer exosomes as drivers of epithelial mesenchymal transition

Exosomes, a subgroup of extracellular vesicles (EVs), have been shown to serve as a conduit for the exchange of genetic information between cells. Exosomes are released from all types of cells but in abundance from cancer cells. The contents of exosomes consist of proteins and genetic material (mRNA, DNA and miRNA) from the cell of origin. In this study, we examined the effects of exosomes derived from human lung cancer serum and both highly metastatic and non-metastatic cells on recipient human bronchial epithelial cells (HBECs). We found that exosomes derived from highly metastatic lung cancer cells and human late stage lung cancer serum induced vimentin expression, and epithelial to mesenchymal transition (EMT) in HBECs. Exosomes derived from highly metastatic cancer cells as well as late stage lung cancer serum induce migration, invasion and proliferation in non-cancerous recipient cells. Our results suggest that cancer derived exosomes could be a potential mediator of EMT in the recipient cells.

A Fhit-mimetic peptide suppresses annexin A4-mediated chemoresistance to paclitaxel in lung cancer cells

We recently reported that Fhit is in a molecular complex with annexin A4 (ANXA4); following to their binding, Fhit delocalizes ANXA4 from plasma membrane to cytosol in paclitaxel-resistant lung cancer cells, thus restoring their chemosensitivity to the drug. Here, we demonstrate that Fhit physically interacts with A4 through its N-terminus; molecular dynamics simulations were performed on a 3D Fhit model to rationalize its mechanism of action. This approach allowed for the identification of the QHLIKPS heptapeptide (position 7 to 13 of the wild-type Fhit protein) as the smallest Fhit sequence still able to preserve its ability to bind ANXA4. Interestingly, Fhit peptide also recapitulates the property of the native protein in inhibiting Annexin A4 translocation from cytosol to plasma membrane in A549 and Calu-2 lung cancer cells treated with paclitaxel. Finally, the combination of Tat-Fhit peptide and paclitaxel synergistically increases the apoptotic rate of cultured lung cancer cells and blocks in vivo tumor formation.

Our findings address to the identification of chemically simplified Fhit derivatives that mimic Fhit tumor suppressor functions; intriguingly, this approach might lead to the generation of novel anticancer drugs to be used in combination with conventional therapies in Fhit-negative tumors to prevent or delay chemoresistance.

Exosome-Derived miR-25-3p and miR-92a-3p Stimulate Liposarcoma Progression

Despite the development of combined modality treatments against liposarcoma in recent years, a significant proportion of patients respond only modestly to such approaches, possibly contributing to local or distant recurrence. Early detection of recurrent or metastatic disease could improve patient prognosis by triggering earlier clinical intervention. However, useful biomarkers for such purposes are lacking. Using both patient plasma samples and cell lines, we demonstrate here that miR-25-3p and miR-92a-3p are secreted by liposarcoma cells through extracellular vesicles and may be useful as potential biomarkers of disease. Both miR-25-3p and miR-92a-3p stimulated secretion of proinflammatory cytokine IL6 from tumor-associated macrophages in a TLR7/8-dependent manner, which in turn promoted liposarcoma cell proliferation, invasion, and metastasis via this interaction with the surrounding microenvironment. Our findings provide novel and previously unreported insight into liposarcoma progression, identifying communication between liposarcoma cells and their microenvironment as a process critically involved in liposarcoma progression. This study establishes the possibility that the pattern of circulating miRNAs may identify recurrence prior to radiological detectability while providing insight into disease outcome and as a possible approach to monitor treatment efficacy. Cancer Res; 77(14); 3846-56. ©2017 AACR.

ERK Activation Globally Downregulates miRNAs through Phosphorylating Exportin-5

MicroRNAs (miRNA) are mostly downregulated in cancer. However, the mechanism underlying this phenomenon and the precise consequence in tumorigenesis remain obscure. Here we show that ERK suppresses pre-miRNA export from the nucleus through phosphorylation of exportin-5 (XPO5) at T345/S416/S497. After phosphorylation by ERK, conformation of XPO5 is altered by prolyl isomerase Pin1, resulting in reduction of pre-miRNA loading. In liver cancer, the ERK-mediated XPO5 suppression reduces miR-122, increases microtubule dynamics, and results in tumor development and drug resistance. Analysis of clinical specimens further showed that XPO5 phosphorylation is associated with poor prognosis for liver cancer patients. Our study reveals a function of ERK in miRNA biogenesis and suggests that modulation of miRNA export has potential clinical implications.

WWOX and p53 Dysregulation Synergize to Drive the Development of Osteosarcoma

Osteosarcoma is a highly metastatic form of bone cancer in adolescents and young adults that is resistant to existing treatments. Development of an effective therapy has been hindered by very limited understanding of the mechanisms of osteosarcomagenesis. Here, we used genetically engineered mice to investigate the effects of deleting the tumor suppressor Wwox selectively in either osteoblast progenitors or mature osteoblasts. Mice with conditional deletion of Wwox in preosteoblasts (Wwox^Δosx1) displayed a severe inhibition of osteogenesis accompanied by p53 upregulation, effects that were not observed in mice lacking Wwox in mature osteoblasts. Deletion of p53 in Wwox^Δosx1 mice rescued the osteogenic defect. In addition, the Wwox;p53^Δosx1 double knockout mice developed poorly differentiated osteosarcomas that resemble human osteosarcoma in histology, location, metastatic behavior, and gene expression. Strikingly, the development of osteosarcomas in these mice was greatly accelerated compared with mice lacking p53 only. In contrast, combined WWOX and p53 inactivation in mature osteoblasts did not accelerate osteosarcomagenesis compared with p53 inactivation alone. These findings provide evidence that a WWOX-p53 network regulates normal bone formation and that disruption of this network in osteoprogenitors results in accelerated osteosarcoma. The Wwox;p53^Δosx1 double knockout establishes a new osteosarcoma model with significant advancement over existing models. Cancer Res; 76(20); 6107-17. ©2016 AACR.

microRNA expression profiling identifies a four microRNA signature as a novel diagnostic and prognostic biomarker in triple negative breast cancers

Triple Negative Breast Cancers (TNBC) is a heterogeneous disease at the molecular and clinical level with poor outcome. Molecular subclassification of TNBCs is essential for optimal use of current therapies and for development of new drugs. microRNAs (miRNA) are widely recognized as key players in cancer progression and drug resistance; investigation of their involvement in a TNBC cohort may reveal biomarkers for diagnosis and prognosis of TNBC. Here we stratified a large TNBC cohort into Core Basal (CB, EGFR and/or CK5, 6 positive) and five negative (5NP) if all markers are negative. We determined the complete miRNA expression profile and found a subset of miRNAs specifically deregulated in the two subclasses.

We identified a 4-miRNA signature given by miR-155, miR-493, miR-30e and miR-27a expression levels, that allowed subdivision of TNBCs not only into CB and 5NP subgroups (sensitivity 0.75 and specificity 0.56; AUC=0.74) but also into high risk and low risk groups. We tested the diagnostic and prognostic performances of both the 5 IHC marker panel and the 4-miRNA expression signatures, which clearly identify worse outcome patients in the treated and untreated subcohorts. Both signatures have diagnostic and prognostic value, predicting outcomes of patient treatment with the two most commonly used chemotherapy regimens in TNBC: anthracycline or anthracycline plus taxanes. Further investigation of the patients' overall survival treated with these regimens show that regardless of IHC group subdivision, taxanes addition did not benefit patients, possibly due to miRNA driven taxanes resistance. TNBC subclassification based on the 5 IHC markers and on the miR-155, miR-493, miR-30e, miR-27a expression levels are powerful diagnostic tools. Treatment choice and new drug development should consider this new subtyping and miRNA expression signature in planning low toxicity, maximum efficacy therapies.

miR-15b/16-2 regulates factors that promote p53 phosphorylation and augments the DNA damage response following radiation in the lung

MicroRNAs (miRNAs) are regulatory RNAs frequently dysregulated in disease and following cellular stress. Investigators have described changes in miR-15b expression following exposure to several stress-inducing anticancer agents, including ionizing radiation (IR), etoposide, and hydrogen peroxide. However, the role for miR-15b as a mediator of cellular injury in organs such as the lung has yet to be explored. In this study, we examined miR-15b expression patterns as well as its potential role in DNA damage and repair in the setting of IR exposure. We showed that miR-15b is up-regulated in a dose- and time-dependent manner in human bronchial epithelial cells following IR. miR-15b expression was highest after 2 h of IR and decreased gradually. Survival rates following IR were also higher in miR-15b/16-2-overexpressing cells. Cell cycle arrest in G2/M phase and an increased DNA repair response were observed in IR-exposed miR-15b/16-2 stable cells. We observed an up-regulation of components of the ataxia telangiectasia mutated (ATM)/Chek1/p53 pathway in miR-15b/16-2-overexpressing cells after IR. Moreover, a pathway-based PCR expression array of genes demonstrated that miR-15b/16-2 overexpression significantly induced the expression of genes involved in ATM/ataxia telangiectasia and Rad-3-related (ATR) signaling, apoptosis, the cell cycle, and DNA repair pathways. Here we demonstrated a novel biological link between miR-15b and DNA damage and cellular protection in lung cells. We identified Wip1 (PPM1D) as a functional target for miR-15b and determined that miR-15b induction of the DNA damage response is partially dependent upon suppression of Wip1. Our study suggests that miR-15b/Wip1 could be a potential therapeutic target in radiation-induced lung disease.

MicroRNA-135b promotes cancer progression by acting as a downstream effector of oncogenic pathways in colon cancer

MicroRNA deregulation is frequent in human colorectal cancers (CRCs), but little is known as to whether it represents a bystander event or actually drives tumor progression in vivo. We show that miR-135b overexpression is triggered in mice and humans by APC loss, PTEN/PI3K pathway deregulation, and SRC overexpression and promotes tumor transformation and progression. We show that miR-135b upregulation is common in sporadic and inflammatory bowel disease-associated human CRCs and correlates with tumor stage and poor clinical outcome. Inhibition of miR-135b in CRC mouse models reduces tumor growth by controlling genes involved in proliferation, invasion, and apoptosis. We identify miR-135b as a key downsteam effector of oncogenic pathways and a potential target for CRC treatment.

Androgen receptor status is a prognostic marker in non-basal triple negative breast cancers and determines novel therapeutic options

Triple negative breast cancers are a heterogeneous group of tumors characterized by poor patient survival and lack of targeted therapeutics. Androgen receptor has been associated with triple negative breast cancer pathogenesis, but its role in the different subtypes has not been clearly defined. We examined androgen receptor protein expression by immunohistochemical analysis in 678 breast cancers, including 396 triple negative cancers. Fifty matched lymph node metastases were also examined. Association of expression status with clinical (race, survival) and pathological (basal, non-basal subtype, stage, grade) features was also evaluated. In 160 triple negative breast cancers, mRNA microarray expression profiling was performed, and differences according to androgen receptor status were analyzed. In triple negative cancers the percentage of androgen receptor positive cases was lower (24.8% vs 81.6% of non-triple negative cases), especially in African American women (16.7% vs 25.5% of cancers of white women). No significant difference in androgen receptor expression was observed in primary tumors vs matched metastatic lesions. Positive androgen receptor immunoreactivity was inversely correlated with tumor grade (p<0.01) and associated with better overall patient survival (p = 0.032) in the non-basal triple negative cancer group. In the microarray study, expression of three genes (HER4, TNFSF10, CDK6) showed significant deregulation in association with androgen receptor status; eg CDK6, a novel therapeutic target in triple negative cancers, showed significantly higher expression level in androgen receptor negative cases (p<0.01). These findings confirm the prognostic impact of androgen receptor expression in non-basal triple negative breast cancers, and suggest targeting of new androgen receptor-related molecular pathways in patients with these cancers.

Generation of mouse lines conditionally over-expressing microRNA using the Rosa26-Lox-Stop-Lox system

MicroRNAs are currently the object of intensive investigation due to their role in a myriad of physiological processes and pathological conditions, such as gene regulation and tumorigenesis. To better understand microRNA function, numerous laboratories have already taken advantage of the available techniques of genome editing in mouse. Here, we describe how to generate genetically engineered mouse lines using the popular Rosa-26 Lox-Stop-Lox Knock-In (Rosa-LSL-KI) targeting. This strategy allows for the selective overexpression of microRNAs of interest when coupled to a tissue-specific Cre-expressing line. The present protocol illustrates in detail both the engineering of the targeting vector and the generation of mutated ES clones ready for injection into mouse blastocysts.

Stathmin regulates mutant p53 stability and transcriptional activity in ovarian cancer

Stathmin is a p53-target gene, frequently overexpressed in late stages of human cancer progression. Type II High Grade Epithelial Ovarian Carcinomas (HG-EOC) represents the only clear exception to this observation. Here, we show that stathmin expression is necessary for the survival of HG-EOC cells carrying a p53 mutant (p53^MUT) gene. At molecular level, stathmin favours the binding and the phosphorylation of p53^MUT by DNA-PK_CS, eventually modulating p53^MUT stability and transcriptional activity. Inhibition of stathmin or DNA-PK_CS impaired p53^MUT–dependent transcription of several M phase regulators, resulting in M phase failure and EOC cell death, both in vitro and in vivo. In primary human EOC a strong correlation exists between stathmin, DNA-PK_CS, p53^MUT overexpression and its transcriptional targets, further strengthening the relevance of the new pathway here described. Overall our data support the hypothesis that the expression of stathmin and p53 could be useful for the identification of high risk patients that will benefit from a therapy specifically acting on mitotic cancer cells.

Integrated microRNA and mRNA signatures associated with survival in triple negative breast cancer

Triple negative breast cancer (TNBC) is a heterogeneous disease at the molecular, pathologic and clinical levels. To stratify TNBCs, we determined microRNA (miRNA) expression profiles, as well as expression profiles of a cancer-focused mRNA panel, in tumor, adjacent non-tumor (normal) and lymph node metastatic lesion (mets) tissues, from 173 women with TNBCs; we linked specific miRNA signatures to patient survival and used miRNA/mRNA anti-correlations to identify clinically and genetically different TNBC subclasses. We also assessed miRNA signatures as potential regulators of TNBC subclass-specific gene expression networks defined by expression of canonical signal pathways.

Tissue specific miRNAs and mRNAs were identified for normal vs tumor vs mets comparisons. miRNA signatures correlated with prognosis were identified and predicted anti-correlated targets within the mRNA profile were defined. Two miRNA signatures (miR-16, 155, 125b, 374a and miR-16, 125b, 374a, 374b, 421, 655, 497) predictive of overall survival (P = 0.05) and distant-disease free survival (P = 0.009), respectively, were identified for patients 50 yrs of age or younger. By multivariate analysis the risk signatures were independent predictors for overall survival and distant-disease free survival. mRNA expression profiling, using the cancer-focused mRNA panel, resulted in clustering of TNBCs into 4 molecular subclasses with different expression signatures anti-correlated with the prognostic miRNAs.

Our findings suggest that miRNAs play a key role in triple negative breast cancer through their ability to regulate fundamental pathways such as: cellular growth and proliferation, cellular movement and migration, Extra Cellular Matrix degradation. The results define miRNA expression signatures that characterize and contribute to the phenotypic diversity of TNBC and its metastasis.

Use of microRNA (miR) expression profiling to identify distinct subclasses of triple-negative breast cancers (TNBC)

1007

Background: TNBC is divided into basal and non-basal subclasses. To further subclassify TNBC we performed microRNA (miR) expression profiles and linked them to patient overall survival. Methods: During 1996-2005, 365 consecutive TNBC (phenotypically estrogen, progesterone and HER2 negative by immunohistochemistry [IHC]) were identified from the NCCN Breast Cancer Data Base/Tumor Registry at OSU Medical Center. One hundred fifty-eight (43%) formalin-fixed paraffin embedded (FFPE) breast cancer and 40 normal breast tissue blocks were available and tissue cores were obtained for RNA. RNA was isolated using the Ambion recoverall total nucleic acid isolation kit and the expression of ~700 miRs was assessed for each sample using the nanoString nCounter method. A consensus-clustering algorithm (ConsensusClusterPlus, Bioconductor www.bioconductor.org) was used to identify subclasses of TNBC and Kaplan-Meier overall survival curves were compared using the log-rank test. Censoring occurred at the date of death from causes other than breast cancer or at time of the last known follow-up, whichever occurred first. The median follow-up was 67 mo. (range 4-171 mo.). Results: The median age was 52 yrs. (range 20-84 yrs.); 81% white and 9% African-American; stages I, II, and III were 31%, 54% and 15%, respectively; and most patients received adjuvant anthracycline-based regimens with (25%) or without taxanes (75%). The algorithm identified 5 distinct subclasses; 1 clustering with normal breast miR expression whereas the other 4 each had a unique pattern of deregulated miRs. The median overall survivals were significantly different across the 5 cancer subclasses (log-rank p=0.028) (Table). Conclusions: miR expression profiling identifies and discriminates 5 TNBC subclasses, which do not coincide with those identified as basal and non-basal by IHC. Molecular analyses are ongoing to associate the miR-based subclasses with specific clinical features or the expression of specific pathways. [Table: see text]

Abstract 2947: B-cell lymphoma in eα-miR-17∼92 transgenic mice

The miR-17∼92 is a polycistronic miRNA cluster, consisting of six miRNAs: miR-17, miR-18a, miR-19a, miR-19b, miR-20a and miR-92a encoded from last exon of a non-coding RNA. It is frequently overexpressed in variety of solid and lymphoid malignancies and has been appropriately called Oncomir-1. Loss-of-function studies revealed a role of miR-17∼92 in heart and lung development, and gain-of-function studies have shown its role in myc induced B-cell lymphomas. In addition to its role in tumorigenesis, the cluster is involved in regulation of lymphocyte development. Some of the key targets of this miRNA include the tumor suppressor, Pten and the proapoptotic, Bim gene. In order to study the mechanisms by which miR-17∼92 overexpression induce tumorigenesis, we generated a B-cell specific transgenic mouse model. The miR-17∼92 overexpression was driven by the eμ enhancer and immunoglobulin heavy chain promoter with a 3′ Green Fluorescent Protein (GFP) tag in order to track the miRNA expression. Expression analysis using Northern Blot and qRT-PCR yielded four founders with significant overexpression of all six miRNAs in their spleens. Quantitative RT-PCR analysis showed significant overexpression of all six miRNAs ranging from 2.5 to 25-fold in spleen cells. Flow cytometry analysis of spleens from 9-month old healthy transgenic mice showed significantly increased CD43+TCR- population as compared to wild type mice. In older mice (18-months) the symptoms are more pronounced with mice developing ascites, enlarged spleen and lymph nodes. The flow analysis of spleens from these mice showed CD19+CD5+ B-cell population similar to human chronic lymphocytic leukemia (CLL). Histological analysis showed multiple organs (lungs, kidney, brain) infiltrated by these lymphoma cells. Southern Blot analysis showed these cells to be oligoclonal B cells, while no T cell clonality was observed. Total mRNA profiling from these malignant cells showed that 782 genes are up- and 1019 genes are down-regulated in transgenic B-cells versus wild type CD19+ B-cells. Ingenuity pathway analysis showed majority of the downregulated genes are represented by Hematological System Development and Function, and Inflammatory Response pathways, while the upregulated genes are represented by cell cycle pathway. Some of the upregulated genes in miR-17∼92 over-expressing malignant B-cells as compared to normal CD19+ B-cells included ZAP-70, CCL5, NONO, previously reported in B-CLL gene signature. Among other overexpressed genes, cJun, cFos and ATF3, were upregulated 5-fold, 67-fold and 18-fold, respectively. We hypothesize that AP-1 dependent transcription may be one of the key survival factors in the miR-17∼92 driven lymphomas. Currently, we are exploring the negative regulators of the oncogenic cJun signaling pathway which may be miR-17∼92 targets. Overall, we found that miR-17∼92 overexpression in mice has the ability to induce B-cell lymphoma which can develop into CLL at an older age.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2947. doi:1538-7445.AM2012-2947

miRNA signatures associate with pathogenesis and progression of osteosarcoma

Osteosarcoma remains a leading cause of cancer death in adolescents. Treatment paradigms and survival rates have not improved in two decades. Driving the lack of therapeutic inroads, the molecular etiology of osteosarcoma remains elusive. MicroRNAs (miRNAs) have demonstrated far-reaching effects on the cellular biology of development and cancer. Their role in osteosarcomagenesis remains largely unexplored. Here we identify for the first time an miRNA signature reflecting the pathogenesis of osteosarcoma from surgically procured samples from human patients. The signature includes high expression of miR-181a,miR-181b, and miR-181c as well as reduced expression of miR-16, miR-29b, and miR-142-5p. We also demonstrate that miR-181b and miR-29b exhibit restricted expression to distinct cell populations in the tumor tissue. Further, higher expression of miR-27a and miR-181c* in pre-treatment biopsy samples characterized patients who developed clinical metastatic disease. In addition, higher expression of miR-451 and miR-15b in pre-treatment samples correlated with subsequent positive response to chemotherapy. In vitro and in vivo functional validation in osteosarcoma cell lines confirmed the tumor suppressive role of miR-16 and the pro-metastatic role of miR-27a. Furthermore, predicted target genes for miR-16 and miR-27a were confirmed as down-regulated by real-time PCR. Affymetrix array profiling of cDNAs from the osteosarcoma specimens and controls were interrogated according to predicted targets of miR-16, miR142-5p, miR-29b, miR-181a/b, and miR-27a. This analysis revealed positive and negative correlations highlighting pathways of known importance to osteosarcoma, as well as novel genes. Thus, our findings establish a miRNA signature associated with pathogenesis of osteosarcoma as well as critical pre-treatment biomarkers of metastasis and responsiveness to therapy.

Anti-miR-135b in colon cancer treatment: Results from a preclinical study

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Background: MicroRNAs (miRs) are small non coding RNAs involved in cell homeostasis. miRs are deregulated in colorectal cancer (CRC). Our study aimed at identifying miRs with a driver role in carcinogenesis altered by similar mechanisms in both human and mouse CRC. Goal of the study was to use CRC mouse models for the pre-clinical development of anti-miRs as therapeutic drugs.

Methods: Azoximetane (AOM)/Dextran-Sulfate (DSS) treated mice or CDX2-CRE/APC-/- mice were used to study inflammation-associated and sporadic APC-related CRC. Human Inflammatory Bowel Disease associated (n=30), and sporadic (n=90) CRC with their matched normal tissues were collected according to Good Clinical Practice recommendation and subjected to RNA extraction using Trizol. miR and gene expression profiling was assessed by nCounter technology (Nanostring Seattle). Anti-miR-135b and scrambled probes for in vivo studies were synthesized by Girindus.

Results: miRs profiling from AOM/DSS and CDX2-CRE/APC-/- CRC. revealed that miR-135b is one of the most up-regulated miRs in both models. In humans miR-135b over-expression was found in both IBD and sporadic CRC and was associated with reduced Progression Free Survival and Overall Survival in CRC patients. Molecular studies in Mouse Embryo Fibroblast and human CRC cell lines highlighted the role of two major pathways in the upstream activation of miR-135b: APC-β-Catenin and SRC-PI3K. MiR-135b up-regulation resulted in reduced apoptosis and increased invasion and metastasis due to the down-regulation of TGFRB2, DAPK1, APC and HIF1AN. Silencing of miR-135b in vivo reduced tumor multiplicity and tumor load in the AOM/DSS CRC model. Mice treated with anti-miR-135b showed well differentiated tumors and microacinar pattern while tumors in the control groups showed low differentiation and adenomatous pattern.

Conclusions: Our data suggest that miR-135b is a key molecule whose activation is downstream of oncogenes and oncosuppressor genes frequently altered in CRC. Our study defines specific pathways that converge on the activation of the same microrna. The “in vivo” silencing of miR-135 shows preclinical efficacy with low toxicity and represents the first in vivo study for the use of antimiRs in CRC treatment.

Abstract B14: Anti-miR-135b in colon cancer treatment

Background: MicroRNAs (miRs) are small non coding RNAs involved in cell homeostasis. miRs are deregulated in colorectal cancer (CRC). Our study aimed at identifying miRs with a driver role in carcinogenesis altered by similar mechanisms in both human and mouse CRC. Goal of the study was to use CRC mouse models for the pre-clinical development of anti-miRs as therapeutic drugs. Methods: Azoximetane (AOM)/Dextran-Sulfate (DSS) treated mice or CDX2Cre-APC f/wt mice were used to study inflammation-associated and sporadic APC-related CRC. Human Inflammatory Bowel Disease associated (n=30), and sporadic (n=90) CRC with their matched normal tissues were collected according to Good Clinical Practice recommendation and subjected to RNA extraction using Trizol. miR and gene expression profiling was assessed by nCounter technology (Nanostring Seattle). AntimiR-135b and scrambled probes for in vivo studies were synthesized by Girindus. Results: miRs profiling from AOM/DSS and CDX2Cre-APC f/wt CRC. revealed that miR-135b is one of the most up-regulated miRs in both models. In humans miR-135b over-expression was found in both IBD and sporadic CRC and was associated with reduced Progression Free Survival and Overall Survival in CRC patients. Molecular studies in Mouse Embryo Fibroblast and human CRC cell lines highlighted the role of two major pathways in the upstream activation of miR-135b: APC-β-Catenin and SRC-PI3K. MiR-135b up-regulation resulted in reduced apoptosis and increased invasion and metastasis due to the down-regulation of TGFRB2, DAPK1, APC and HIF1AN. Silencing of miR-135b in vivo reduced tumor multiplicity and tumor load in the AOM/DSS CRC model. Mice treated with anti-miR-135b showed well differentiated tumors and acinar pattern while tumors in the control groups showed low differentiation and adenomatous pattern. Conclusions: Our data suggest that miR-135b is a key molecule whose activation is downstream of oncogenes and oncosuppressor genes frequently altered in CRC. Our study defines specific pathways that converge on the activation of the same microrna. The “in vivo” silencing of miR-135 shows preclinical efficacy with low toxicity and represents the first in vivo study for the use of antimiRs in CRC treatment

Note: This abstract was not presented at the conference because the presenter was unable to attend.

Citation Format: Nicola Valeri, Roberta Gafa', Gerard Nuovo, Giovanni Lanza, Wendy Frankel, Peter K. Vogt, Joanna Groden, Michael Karin, Carlo M. Croce, Chiara Braconi, Pierluigi Gasparini, Sergei Grivennikov, Jonathan R. Hart, Alessio Paone, Francesca Lovat, Muller Fabbri. Anti-miR-135b in colon cancer treatment [abstract]. In: Proceedings of the AACR Special Conference on Noncoding RNAs and Cancer; 2012 Jan 8-11; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Res 2012;72(2 Suppl):Abstract nr B14.

MicroRNAs in the pathogenesis of cancer

MicroRNAs (miRs) are small (19-25 nucleotides) non-protein-coding RNAs involved in development, differentiation, and aging; they act by inducing messenger RNA (mRNA) silencing through degradation, and post-transcriptional or decoy activity. miR profiles of human solid and hematologic malignancies have highlighted their potential value as tumor markers in cancer patient management. Different experimental lines of evidence have confirmed that deregulation of miRs not only results as consequence of cancer progression but also directly promotes tumor initiation and progression in a cause-effect manner. These findings reveal a potential and appealing role for miRs as cancer therapeutic targets. This review focuses on the causes and consequences of miR deregulation in carcinogenesis and tumor progression. The work aims at providing the molecular bases for the understanding of the potential role of miRs in the translational and clinical setting.

EGFR and MET receptor tyrosine kinase-altered microRNA expression induces tumorigenesis and gefitinib resistance in lung cancers

The involvement of the MET oncogene in de novo and acquired resistance of non-small cell lung cancers (NSCLCs) to tyrosine kinase inhibitors (TKIs) has previously been reported, but the precise mechanism by which MET overexpression contributes to TKI-resistant NSCLC remains unclear. MicroRNAs (miRNAs) negatively regulate gene expression, and their dysregulation has been implicated in tumorigenesis. To understand their role in TKI-resistant NSCLCs, we examined changes in miRNA that are mediated by tyrosine kinase receptors. Here we report that miR-30b, miR-30c, miR-221 and miR-222 are modulated by both epidermal growth factor (EGF) and MET receptors, whereas miR-103 and miR-203 are controlled only by MET. We showed that these miRNAs have important roles in gefitinib-induced apoptosis and epithelial-mesenchymal transition of NSCLC cells in vitro and in vivo by inhibiting the expression of the genes encoding BCL2-like 11 (BIM), apoptotic peptidase activating factor 1 (APAF-1), protein kinase C ɛ (PKC-ɛ) and sarcoma viral oncogene homolog (SRC). These findings suggest that modulation of specific miRNAs may provide a therapeutic approach for the treatment of NSCLCs.

miR-130a targets MET and induces TRAIL-sensitivity in NSCLC by downregulating miR-221 and 222

Non-small cell lung cancer (NSCLC) accounts for ∼80% of all lung cancers. Although some advances in lung cancer therapy have been made, patient survival is still quite poor. Two microRNAs, miR-221 and miR-222, upregulated by the MET proto-oncogene, have been already described to enhance cell survival and to induce TNF-related apoptosis-inducing ligand (TRAIL) resistance in NSCLC cell lines, through the downregulation of p27(kip1), PTEN and TIMP3. Here, we further investigated this pathway and showed that miR-130a, expressed at low level in lung cancer cell lines, by targeting MET was able to reduce TRAIL resistance in NSCLC cells through the c-Jun-mediated downregulation of miR-221 and miR-222. Moreover, we found that miR-130a reduced migratory capacity of NSCLC. A better understanding of MET-miR-221 and 222 axis regulation in drug resistance is the key in developing new strategies in NSCLC therapy.

Role of T198 modification in the regulation of p27(Kip1) protein stability and function

The tumor suppressor gene p27^Kip1 plays a fundamental role in human cancer progression. Its expression and/or functions are altered in almost all the different tumor histotype analyzed so far. Recently, it has been demonstrated that the tumor suppression function of p27 resides not only in the ability to inhibit Cyclins/CDKs complexes through its N-terminal domain but also in the capacity to modulate cell motility through its C-terminal portion. Particular interest has been raised by the last amino-acid, (Threonine 198) in the regulation of both protein stability and cell motility.

Here, we describe that the presence of Threonine in position 198 is of primary importance for the regulation of the protein stability and for the control of cell motility. However, while the control of cell motility is dependent on the phosphorylation of T198, the stability of the protein is specifically controlled by the steric hindrance of the last amino acid. The effects of T198 modification on protein stability are not linked to the capacity of p27 to bind Cyclins/CDKs complexes and/or the F-box protein Skp2. Conversely, our results support the hypothesis that conformational changes in the disordered structure of the C-terminal portion of p27 are important in its ability to be degraded via a proteasome-dependent mechanism. On the other hand T198 phosphorylation favors p27/stathmin interaction eventually contributing to the regulation of cell motility, supporting the hypothesis that the presence of T198 is fundamental for the regulation of p27 functions.

Effect of miR-21 on resistance to 5-fluorouracil and regulation of MSH2

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Background: MicroRNAs are small non coding RNAs controlling cell homeostasis. Defects in mismatch repair (MMR) genes cause resistance to 5-fluorouracil (5FU). miR-21 is up-regulated in colorectal cancer (CRC) and is associated with poor benefit from adjuvant 5FU. We aimed at studying if miR-21 may induce 5FU resistance by down-regulating MSH2.

Methods: Fresh frozen (32) and paraffin-embedded (50) cases of CRC and matched normal tissues were studied for miR-21 expression (Northern Blotting and in situ Hybridization) and MSH2 expression (Western Blotting and Immunohistochemistry). CRC Colo-320DM, SW620 and isogenic Lovo cells with [Lovo(MSH2+)] and without MSH2 [Lovo(MSH2-)] were used. Pre-miR-21 was used for over-expression experiments. Luciferase vectors with MSH2 (Luc-MSH2) and MSH6 (Luc-MSH6) 3'UTRs downstream of the Luciferase gene were used. Cell cycle modifications after 5FU (10uM) were assessed by FACS analysis. Lentiviral vectors encoding for miR-21 or siRNA to MSH2 or empty vectors were used for stable infection. Stable clones were injected in the flank of nude mice. Mice were treated with 5FU i.p. for 2 weeks. Tumor volume was measured once a week and calculated according to the formula Volume=LxW2/2.

Results: A statistically significant inverse correlation between miR-21 and MSH2 expression was observed by Parson's test in the two CRC cohorts. miR-21 over-expression caused reduction in MSH2 and MSH6 protein expression and in Luciferase activity after transfection with Luc-MSH2 or Luc-MSH6 vectors confirming that miR-21 directly regulates MSH2 and MSH6. miR-21 up-regulation reduced 5FU induced apoptosis and G2/M arrest at the same extent of siRNA to MSH2 in all MMR proficient cells while no significant effect was observed in Lovo(MSH2-). Complementation experiments with plasmid encoding for MSH2 promoted 5FU induced apoptosis that was inhibited by co-transfection with miR-21. Xenograft tumors over-expressing miR-21 or siRNA anti MSH2 achieved the same response to 5FU and both showed to be less responsive to 5FU than controls.

Conclusions: miR-21 causes resistance to 5FU in a MSH2 dependent manner and might be a useful marker in predicting therapeutic outcome in CRC patients.

No significant financial relationships to disclose.

The insulin-like growth factor receptor I promotes motility and invasion of bladder cancer cells through Akt- and mitogen-activated protein kinase-dependent activation of paxillin

The insulin-like growth factor receptor I (IGF-IR) plays an essential role in transformation by promoting cell growth and protecting cancer cells from apoptosis. Aberrant IGF-IR signaling is implicated in several types of tumors, including carcinomas of the lung, breast, prostate, pancreas, liver, and colon. However, the contribution of the IGF-IR to the development of the transformed phenotype in urothelial cells has not been clearly established. In this study we demonstrated that the IGF-IR is overexpressed in invasive bladder cancer tissues compared with nonmalignant controls. We have investigated the role of the IGF-IR in bladder cancer by using urothelial carcinoma-derived 5637 and T24 cells. Although activation of the IGF-IR did not appreciably affect their growth, it did promote migration and stimulate in vitro wound closure and invasion. These effects required the activation of the Akt and Mitogen-activated protein kinase (MAPK) pathways as well as IGF-I-induced Akt- and MAPK-dependent phosphorylation of paxillin, which relocated at dynamic focal adhesions and was necessary for promoting motility in bladder cancer cells. Our results provide the first evidence for a role of the IGF-IR in motility and invasion of bladder cancer cells and support the hypothesis that the IGF-IR may play a critical role in the establishment of the invasive phenotype in urothelial neoplasia. Thus, the IGF-IR may also serve as a novel biomarker for bladder cancer.

Abstract 5057: The insulin-like growth factor receptor I promotes motility and invasion of bladder cancer cells through Akt- and MAPK-dependent activation of paxillin

The insulin-like growth factor receptor I (IGF-IR) plays an essential role in transformation by promoting cell growth and protecting cancer cells from apoptosis. Aberrant IGF-IR signaling is implicated in several types of tumors, including carcinomas of the lung, breast, prostate, pancreas, liver and colon. However, whether the IGF-IR contributes to the transforming phenotype of urothelial cells has not been clearly established but recent data suggest that the IGF-IR is over-expressed in bladder cancer.

In this study we demonstrated by immunohistochemical analysis that the IGF-IR is over-expressed in invasive bladder cancer (T3/T4) tissues compared to non-malignant controls. We have also characterized the mechanism of action of the IGF-IR in cancer urothelial cells using urothelial carcinoma-derived 5637 and T24 cells. Although activation of the IGF-IR did not appreciably affect their growth, it did promote migration and stimulate in vitro wound closure and invasion through extracellular matrix. These effects required the activation of the Akt and MAPK pathways and IGF-I induced Akt- and MAPK-dependent phosphorylation of paxillin, which relocated at dynamic focal adhesions at the protruding edge of migrating urothelial cancer cells. Using siRNA strategies we also demonstrated that paxillin was necessary for promoting IGF-I-mediated motility and invasion in bladder cancer cells.

In conclusion, our results provide the first evidence for a role of the IGF-IR in motility and invasion of bladder cancer cells, and support the hypothesis that the IGF-IR may play a critical role in the establishment of the invasive phenotype in urothelial neoplasia. The IGF-IR could represent a novel molecular target in bladder cancer and could also serve as a novel tumor biomarker for diagnosis and possibly prognosis of bladder tumors.

This work has been supported by the Benjamin Perkins Bladder Cancer Fund, the Martin Greitzer Fund and National Institutes of Health Grants RO1 DK068419 (A.M.) and RO1 CA39481 and RO1 CA047282 (R.V.I.).

§Present address: Medimmune, One Medimmune Way, Gaithersburg, MD 20878

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5057.

Proepithelin is an autocrine growth factor for bladder cancer

The growth factor proepithelin functions as an important regulator of proliferation and motility. Proepithelin is overexpressed in a great variety of cancer cell lines and clinical specimens of breast, ovarian and renal cancer, as well as glioblastomas. Using recombinant proepithelin on 5637 transitional cell carcinoma-derived cells, we have shown previously that proepithelin plays a critical role in bladder cancer by promoting motility of bladder cancer cells. In this study, we used the ONCOMINE database and gene microarray analysis tool to analyze proepithelin expression in several bladder cancer microarray studies. We found a statistically significant increase in proepithelin messenger RNA expression in bladder cancers vis-à-vis non-neoplastic tissues, and this was associated with pathologic and prognostic parameters. Targeted downregulation of proepithelin in T24 transitional carcinoma cells with small hairpin RNA inhibited both Akt and mitogen-activated protein kinase pathways, severely reduced the ability of T24 cells to proliferate in the absence of serum and inhibited migration, invasion and wound healing. In support of these in vitro results, we discovered that proepithelin expression was significantly upregulated in invasive bladder cancer tissues compared with normal urothelium. In addition, proepithelin was secreted in the urine, where it was detectable by immunoblotting and enzyme-linked immunosorbent assay. Collectively, these results support the hypothesis that proepithelin may play a critical role as an autocrine growth factor in the establishment and progression of bladder cancer and suggest that proepithelin may prove a novel biomarker for the diagnosis and prognosis of bladder neoplasms.

Proepithelin regulates prostate cancer cell biology by promoting cell growth, migration, and anchorage-independent growth

The growth factor proepithelin has recently emerged as an important regulator of transformation in several physiological and pathological systems. In this study, we determined the biological roles of proepithelin in prostate cancer cells using purified human recombinant proepithelin as well as proepithelin-depletion strategies. Proepithelin promoted the migration of androgen-dependent and -independent human prostate cancer cells; androgen-independent DU145 cells were the more responsive. In these cells, proepithelin additionally stimulated wound closure, invasion, and promotion of cell growth in vitro. These effects required the activation of both the Akt and mitogen-activated protein kinase pathways. We have analyzed proepithelin expression levels in different available prostate cancer microarray studies using the Oncomine database and found a statistically significant increase in proepithelin mRNA expression levels in prostate cancers compared with nonneoplastic controls. Notably, depletion of endogenous proepithelin by siRNA and antisense strategies impaired the ability of DU145 cells to grow and migrate after serum withdrawal and inhibited anchorage-independent growth. Our results provide the first evidence for a role of proepithelin in stimulating the migration, invasion, proliferation, and anchorage-independent growth of prostate cancer cells. This study supports the hypothesis that proepithelin may play a critical role as an autocrine growth factor in the establishment and initial progression of prostate cancer. Furthermore, proepithelin may prove to be a useful clinical marker for the diagnosis of prostate tumors.

Targeted intraoperative radiotherapy impairs the stimulation of breast cancer cell proliferation and invasion caused by surgical wounding

PURPOSE

After apparently successful excision of breast cancer, risk of local recurrence remains high mainly in the area surrounding the original tumor, indicating that wound healing processes may be implicated. The proportional reduction of this risk by radiotherapy does not depend on the extent of surgery, suggesting that radiotherapy, in addition to killing tumor cells, may influence the tumor microenvironment.

EXPERIMENTAL DESIGN

We studied how normal and mammary carcinoma cell growth and motility are affected by surgical wound fluids (WF), collected over 24 h following breast-conserving surgery in 45 patients, 20 of whom had received additional TARGeted Intraoperative radioTherapy (TARGIT), immediately after the surgical excision. The proteomic profile of the WF and their effects on the activation of intracellular signal transduction pathways of breast cancer cells were also analyzed.

RESULTS

WF stimulated proliferation, migration, and invasion of breast cancer cell lines. The stimulatory effect was almost completely abrogated when fluids from TARGIT-treated patients were used. These fluids displayed altered expression of several cytokines and failed to properly stimulate the activation of some intracellular signal transduction pathways, when compared with fluids harvested from untreated patients.

CONCLUSIONS

Delivery of TARGIT to the tumor bed alters the molecular composition and biological activity of surgical WF. This novel antitumoral effect could, at least partially, explain the very low recurrence rates found in a large pilot study using TARGIT. It also opens a novel avenue for identifying new molecular targets and testing novel therapeutic agents.

Stathmin activity influences sarcoma cell shape, motility, and metastatic potential

The balanced activity of microtubule-stabilizing and -destabilizing proteins determines the extent of microtubule dynamics, which is implicated in many cellular processes, including adhesion, migration, and morphology. Among the destabilizing proteins, stathmin is overexpressed in different human malignancies and has been recently linked to the regulation of cell motility. The observation that stathmin was overexpressed in human recurrent and metastatic sarcomas prompted us to investigate stathmin contribution to tumor local invasiveness and distant dissemination. We found that stathmin stimulated cell motility in and through the extracellular matrix (ECM) in vitro and increased the metastatic potential of sarcoma cells in vivo. On contact with the ECM, stathmin was negatively regulated by phosphorylation. Accordingly, a less phosphorylable stathmin point mutant impaired ECM-induced microtubule stabilization and conferred a higher invasive potential, inducing a rounded cell shape coupled with amoeboid-like motility in three-dimensional matrices. Our results indicate that stathmin plays a significant role in tumor metastasis formation, a finding that could lead to exploitation of stathmin as a target of new antimetastatic drugs.

p27(kip1) functional regulation in human cancer: a potential target for therapeutic designs

The mitotic cell cycle is a tightly regulated process that ensures the correct division of one cell into two daughter cells. Progress along the different phases of the cell cycle is positively regulated by the sequential activation of a family of serine-threonine kinases called CDKs (Cyclin Dependent Kinases). Their activity is counteracted by small proteins known as CDK inhibitors (CKI) that ensure the correct timing of CDK activation in the different phases of the cell cycle. The present review will deal with the role of one of this CKI, p27(kip1), in human cancer, focusing in particular on the mechanisms underlying its functional inactivation in tumor cells. p27(kip1) protein downregulation is usually achieved by proteasomal degradation and is often correlated to a worse prognosis in several types of human cancers, resulting in the reduction of disease free and overall survival. More recently, it has been proposed that p27(kip1) protein, rather than degraded, can be functionally inactivated. The mechanisms and the implications of these two types of p27(kip1) deregulation will be discussed and some potential therapeutic approaches targeting p27(kip1) functions will be proposed.