Targeting Focal Adhesion Kinase and Resistance to mTOR Inhibition in Pancreatic Neuroendocrine Tumors

Protective Autophagy Attenuates the Cytotoxicity of MTI-31 in Renal Cancer Cells by Activating the ERK Pathway

The mammalian target of rapamycin (mTOR) is a key regulatory molecular target to treat cancer, and MTI-31 is a potent mTOR inhibitory agent for the therapeutically target of the renal cell carcinoma (RCC). However, the therapeutic efficacy of MTI-31 is limited by multiple factors, including autophagy. MTI-31 can activate cells to generate autophagy, which may in turn indirectly affect cell proliferation and apoptosis. We aimed to observe changes in cell protective autophagy via the ERK pathway and explore the potential mechanism underlying drug resistance of RCC cells to MTI-31. Different concentrations of 786-O and RCC4 cells were co-cultured with MTI-31 for distinct durations. The result of autophagy marker detection by Western blot showed that MTI-31 could induce RCC cells to produce autophagy in a dose and time-dependent manner. After treating the RCC cells with the autophagy inhibitor chloroquine (CQ), CCK8 and Western blot assays demonstrated that CQ could effectively enhance cell apoptosis induced by MTI-31 and that the autophagy induced by MTI-31 was cytoprotective. In addition, CCK8 and Western blot demonstrated that MTI-31 exerted its effect by activating the ERK pathway rather than the JNK or p38 pathway. The use of the ERK inhibitor AZD6244 to block the ERK pathway could effectively promote cell apoptosis induced by MTI-31. AZD6244 attenuated the autophagy induced by MTI-31 and increased the cytotoxicity of MTI-31. Western blot also demonstrated that MTI-31-induced autophagy was mediated by the downstream regulators of ERK pathways, including Beclin-1 and Bcl-2. It demonstrated that the MTI-31 mediated activation ERK pathway is associated with the induction of autophagy, and autophagy can attenuate the cytotoxicity of MTI-31 on RCC cells. In summary, inhibition of ERK pathway-mediated autophagy can rectify drug resistance to MTI-31 effectively.

Combining MTI-31 with RAD001 inhibits tumor growth and invasion of kidney cancer by activating autophagy

At most of the times, patients who are diagnosed with kidney cancer should be provided with systemic treatment as drug resistance is a challenging issue in the treatment of this disease. The progression of the cancer can be inhibited with the help of mTOR inhibitors namely RAD001 (everolimus) and MTI-31. In literature, it has been revealed that these mTOR inhibitors have the potential to stimulate autophagy. This degradation pathway boosts the survival rate of the cancerous cells that are subjected to anti-cancer therapy. In this study, CCK8, colony formation assays, and ethynyl deoxyuridine (EdU) analysis were conducted to detect cell proliferation. Furthermore, Transwell assays were also conducted for cell migration analysis. In addition to these, the researchers also performed the flow cytometry process to identify the cells that are undergoing apoptosis. In vivo, experiments were conducted to measure the growth of tumors and metastasis. In this study, the treatment provided through a combination of MTI-31 and RAD001 significantly inhibited the kidney cancer cells' proliferation and tumor growth. Furthermore, there was a notable reduction in the migration and invasion of kidney cancer cells upon the neighboring cells. The outcomes from the mechanistic studies infer that the combination of MTI-31 and RAD001 increases the LC3 levels, which in turn translates into the activation of autophagy. To conclude, the combination of MTI-31 and RAD001 improves the anti-cancerous impact produced by RAD001 in vivo through the promotion of autophagy.

C1QA and COMP: plasma-based biomarkers for early diagnosis of pancreatic neuroendocrine tumors

Pancreatic Neuroendocrine tumors (PanNET) are challenging to diagnose and often detected at advanced stages due to a lack of specific and sensitive biomarkers. This study utilized proteomics as a valuable approach for cancer biomarker discovery; therefore, mass spectrometry-based proteomic profiling was conducted on plasma samples from 12 subjects (3 controls; 5 Grade I, 4 Grade II PanNET patients) to identify potential proteins capable of effectively distinguishing PanNET from healthy controls. Data are available via ProteomeXchange with the identifier PXD045045. 13.2% of proteins were uniquely identified in PanNET, while 60% were commonly expressed in PanNET and controls. 17 proteins exhibiting significant differential expression between PanNET and controls were identified with downstream analysis. Further, 5 proteins (C1QA, COMP, HSP90B1, ITGA2B, and FN1) were selected by pathway analysis and were validated using Western blot analysis. Significant downregulation of C1QA (p = 0.001: within groups, 0.03: control vs. grade I, 0.0013: grade I vs. grade II) and COMP (p = 0.011: within groups, 0.019: control vs grade I) were observed in PanNET Grade I & II than in controls. Subsequently, ELISA on 38 samples revealed significant downregulation of C1QA and COMP with increasing disease severity. This study shows the potential of C1QA and COMP in the early detection of PanNET, highlighting their role in the search for early-stage (Grade-I and Grade-II) diagnostic markers and therapeutic targets for PanNET.

Back to the future: targeting the extracellular matrix to treat systemic sclerosis

Fibrosis is the excessive deposition of a stable extracellular matrix (ECM); fibrotic tissue is composed principally of highly crosslinked type I collagen and highly contractile myofibroblasts. Systemic sclerosis (SSc) is a multisystem autoimmune connective tissue disease characterized by skin and organ fibrosis. The fibrotic process has been recognized in SSc for >40 years, but drugs with demonstrable efficacy against SSc fibrosis in ameliorating the lung involvement have only recently been identified. Unfortunately, these treatments are ineffective at improving the skin score in patients with SSc. Previous clinical trials in SSc have largely focused on the cross-purposing of anti-inflammatory drugs and the use of immunosuppressive drugs from the transplantation field, which address inflammatory and/or autoimmune processes. Limited examination has taken place of specific anti-fibrotic agents developed through their ability to directly target the ECM in SSc by, for example, alleviating the persistent matrix stiffness and mechanotransduction that might be required for both the initiation and maintenance of fibrosis, including in SSc. However, because of the importance of the ECM in the SSc phenotype, attempts have now been made to identify drugs that specifically target the ECM, including some drugs that are currently under consideration for the treatment of cancer.

High frequency of alternative splicing variants of the oncogene Focal Adhesion Kinase in neuroendocrine tumors of the pancreas and breast

The characteristic genetic abnormality of neuroendocrine neoplasms (NENs), a heterogeneous group of tumors found in various organs, remains to be identified. Here, based on the analysis of the splicing variants of an oncogene Focal Adhesion Kinase (FAK) in The Cancer Genome Atlas datasets that contain 9193 patients of 33 cancer subtypes, we found that Box 6/Box 7-containing FAK variants (FAK6/7) were observed in 7 (87.5%) of 8 pancreatic neuroendocrine carcinomas and 20 (11.76%) of 170 pancreatic ductal adenocarcinomas (PDACs). We tested FAK variants in 157 tumor samples collected from Chinese patients with pancreatic tumors, and found that FAK6/7 was positive in 34 (75.6%) of 45 pancreatic NENs, 19 (47.5%) of 40 pancreatic solid pseudopapillary neoplasms, and 2 (2.9%) of 69 PDACs. We further tested FAK splicing variants in breast neuroendocrine carcinoma (BrNECs), and found that FAK6/7 was positive in 14 (93.3%) of 15 BrNECs but 0 in 23 non-NEC breast cancers. We explored the underlying mechanisms and found that a splicing factor serine/arginine repetitive matrix protein 4 (SRRM4) was overexpressed in FAK6/7-positive pancreatic tumors and breast tumors, which promoted the formation of FAK6/7 in cells. These results suggested that FAK6/7 could be a biomarker of NENs and represent a potential therapeutic target for these orphan diseases.

A systems biology approach to define mechanisms, phenotypes, and drivers in PanNETs with a personalized perspective

Pancreatic neuroendocrine tumors (PanNETs) are a rare tumor entity with largely unpredictable progression and increasing incidence in developed countries. Molecular pathways involved in PanNETs development are still not elucidated, and specific biomarkers are missing. Moreover, the heterogeneity of PanNETs makes their treatment challenging and most approved targeted therapeutic options for PanNETs lack objective responses. Here, we applied a systems biology approach integrating dynamic modeling strategies, foreign classifier tailored approaches, and patient expression profiles to predict PanNETs progression as well as resistance mechanisms to clinically approved treatments such as the mammalian target of rapamycin complex 1 (mTORC1) inhibitors. We set up a model able to represent frequently reported PanNETs drivers in patient cohorts, such as Menin-1 (MEN1), Death domain associated protein (DAXX), Tuberous Sclerosis (TSC), as well as wild-type tumors. Model-based simulations suggested drivers of cancer progression as both first and second hits after MEN1 loss. In addition, we could predict the benefit of mTORC1 inhibitors on differentially mutated cohorts and hypothesize resistance mechanisms. Our approach sheds light on a more personalized prediction and treatment of PanNET mutant phenotypes.

Robust identification of common genomic biomarkers from multiple gene expression profiles for the prognosis, diagnosis, and therapies of pancreatic cancer

Pancreatic cancer (PC) is one of the leading causes of cancer-related death globally. So, identification of potential molecular signatures is required for diagnosis, prognosis, and therapies of PC. In this study, we detected 71 common differentially expressed genes (cDEGs) between PC and control samples from four microarray gene-expression datasets (GSE15471, GSE16515, GSE71989, and GSE22780) by using robust statistical and machine learning approaches, since microarray gene-expression datasets are often contaminated by outliers due to several steps involved in the data generating processes. Then we detected 8 cDEGs (ADAM10, COL1A2, FN1, P4HB, ITGB1, ITGB5, ANXA2, and MYOF) as the PC-causing key genes (KGs) by the protein-protein interaction (PPI) network analysis. We validated the expression patterns of KGs between case and control samples by box plot analysis with the TCGA and GTEx databases. The proposed KGs showed high prognostic power with the random forest (RF) based prediction model and Kaplan-Meier-based survival probability curve. The KGs regulatory network analysis detected few transcriptional and post-transcriptional regulators for KGs. The cDEGs-set enrichment analysis revealed some crucial PC-causing molecular functions, biological processes, cellular components, and pathways that are associated with KGs. Finally, we suggested KGs-guided five repurposable drug molecules (Linsitinib, CX5461, Irinotecan, Timosaponin AIII, and Olaparib) and a new molecule (NVP-BHG712) against PC by molecular docking. The stability of the top three protein-ligand complexes was confirmed by molecular dynamic (MD) simulation studies. The cross-validation and some literature reviews also supported our findings. Therefore, the finding of this study might be useful resources to the researchers and medical doctors for diagnosis, prognosis and therapies of PC by the wet-lab validation.

Potential effective diagnostic biomarker in patients with primary and metastatic small intestinal neuroendocrine tumors

Background: Small intestinal neuroendocrine tumors (SI-NETs) are the most common malignant tumors of the small intestine, with many patients presenting with metastases and their incidence increasing. We aimed to find effective diagnostic biomarkers for patients with primary and metastatic SI-NETs that could be applied for clinical diagnosis. Methods: We downloaded GSE65286 (training set) and GSE98894 (test set) from the GEO database and performed differential gene expression analysis to obtain differentially expressed genes (DEGs) and differentially expressed long non-coding RNAs (DElncRNAs). The functions and pathways involved in these genes were further explored by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. In addition, a global regulatory network involving dysregulated genes in SI-NETs was constructed based on RNAInter and TRRUST v2 databases, and the diagnostic power of hub genes was identified by receiver operating characteristic curve (ROC). Results: A total of 2,969 DEGs and DElncRNAs were obtained in the training set. Enrichment analysis revealed that biological processes (BPs) and KEGG pathways were mainly associated with cancer. Based on gene set enrichment analysis (GSEA), we obtained five BPs (cytokinesis, iron ion homeostasis, mucopolysaccharide metabolic process, platelet degranulation and triglyceride metabolic process) and one KEGG pathway (ppar signaling pathway). In addition, the core set of dysregulated genes obtained included MYL9, ITGV8, FGF2, FZD7, and FLNC. The hub genes were upregulated in patients with primary SI-NETs compared to patients with metastatic SI-NETs, which is consistent with the training set. Significantly, the results of ROC analysis showed that the diagnostic power of the hub genes was strong in both the training and test sets. Conclusion: In summary, we constructed a global regulatory network in SI-NETs. In addition, we obtained the hub genes including MYL9, ITGV8, FGF2, FZD7, and FLNC, which may be useful for the diagnosis of patients with primary and metastatic SI-NETs.

FAM83A promotes the progression and metastasis of human pancreatic neuroendocrine tumors by inducing the epithelial-mesenchymal transition via the PI3K/AKT and ERK pathways

PURPOSE

Family with sequence similarity 83, member A (FAM83A) has been reported to play an important role in cancer progression and metastasis. The purpose of this study was to clarify the role and mechanism of FAM83A in pancreatic neuroendocrine tumors (PanNETs).

METHODS

PanNET specimens and adjacent nontumor pancreatic tissues obtained from 68 patients who underwent curative surgery for PanNETs were assessed for FAM83A expression using immunochemical staining. The relationships between FAM83A expression, clinicopathological parameters and prognosis were statistically analyzed. PanNET cell lines were used to study the role of FAM83A in the progression and metastasis of PanNETs in vitro and in vivo.

RESULTS

FAM83A was overexpressed in PanNET specimens compared with adjacent nontumor tissues. Furthermore, FAM83A expression was closely associated with lymph node metastasis (P = 0.02), perineural invasion (P = 0.001), WHO classification (P = 0.039), AJCC stage (P = 0.01) and shorter disease-free survival in patients with PanNETs (P < 0.001). FAM83A overexpression effectively promoted PanNET cell proliferation, migration, invasion and growth both in vitro and in vivo, whereas FAM83A inhibition exerted the opposite effects. Subsequent mechanistic investigations revealed that FAM83A promotes the progression and metastasis of PanNETs by inducing epithelial-mesenchymal transition (EMT) via the PI3K/AKT and ERK pathways.

CONCLUSIONS

FAM83A plays an important role in the progression and metastasis of PanNET by inducing the EMT via the activation of the ERK and PI3K/AKT pathways and may serve as a valuable molecular target in PanNET treatment.

RIOK3 promotes pancreatic ductal adenocarcinoma cell invasion and metastasis by stabilizing FAK

Pancreatic ductal adenocarcinoma (PDAC) is an extremely aggressive cancer, characterized by a high metastatic burden. RIO Kinase 3 (RIOK3) has been shown to promote invasion and metastasis of PDAC by cytoskeleton remodeling, but the exact mechanism is still unknown. In this study, we analyzed transcriptome sequencing data from RIOK3 stable knockdown PANC-1 cells and TCGA-PDAC data and discovered that RIOK3 was substantially related to focal adhesion signaling in PDAC. Additionally, silencing RIOK3 dramatically decreased Focal Adhesion Kinase (FAK) protein expression and phosphorylation (Tyr397 and Tyr925 sites). Immunoprecipitation assay verified the interaction of RIOK3 and FAK. Furthermore, RIOK3 considerably increased the protein stability of FAK protein but not FAK-Y925F protein. The biological function of RIOK3 in increasing PDAC cell invasion and migration was shown to be dependent on FAK activation. Moreover, we discovered that RIOK3 mutations were mainly characterized by amplification. RIOK3 mRNA was found to be significantly elevated in PDAC tissues and was associated with a poor prognosis. Furthermore, RIOK3 mRNA was significantly upregulated in later T-stage, pre-existing lymph node metastases, and later pathological stage samples. Overall, our study found that RIOK3 promotes PDAC cell invasion and metastasis by stabilizing FAK protein expression and upregulating its phosphorylation. This also provides a new target for therapeutic modalities targeting FAK.

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FAK activation is required for RIOK3 to promote PDAC cell invasion and metastasis.

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RIOK3 binds to and stabilizes the FAK protein.

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RIOK3 is highly expressed in PDAC tissues and associated with poor prognosis.

Focal Adhesion Kinase Provides a Collateral Vulnerability That Can Be Leveraged to Improve mTORC1 Inhibitor Efficacy

The PI3K/AKT/mTORC1 pathway is a major therapeutic target for many cancers, particularly breast cancer. Everolimus is an mTORC1 inhibitor used in metastatic estrogen receptor-positive (ER+) and epidermal growth factor receptor 2-negative (HER2-) breast cancer. However, mTORC1 inhibitors have limited efficacy in other breast cancer subtypes. We sought to discover collateral sensitivities to mTORC1 inhibition that could be exploited to improve therapeutic response. Using a mouse model of breast cancer that is intrinsically resistant to mTORC1 inhibition, we found that rapamycin alters the expression of numerous extracellular matrix genes, suggesting a potential role for integrins/FAK in controlling mTORC1-inhibitor efficacy. FAK activation was also inversely correlated with rapamycin response in breast cancer cell lines. Supporting its potential utility in patients, FAK activation was observed in >50% of human breast cancers. While blocking FAK in mouse models of breast cancer that are highly responsive to rapamycin had no impact on tumor growth, FAK inhibition sensitized rapamycin-resistant tumors to mTORC1 inhibition. These data reveal an innate dependency on FAK when mTORC1 signaling is lost in tumors that are resistant to mTORC1 inhibitors. They also suggest a precision medicine approach to improving mTORC1 inhibitor efficacy in resistant cancers by suppressing FAK signaling.

Repurposing therapeutics for malignant pleural mesothelioma (MPM) - Updates on clinical translations and future outlook

INTRODUCTION

Malignant pleural mesothelioma (MPM) is a rare malignancy affecting the mesothelial cells in the pleural lining surrounding the lungs. First approved chemotherapy against MPM was a platinum/antifolate (cisplatin/pemetrexed) (2003). Since then, no USFDA approvals have gone through for small molecules as these molecules have not been proven to be therapeutically able in later stages of clinical studies. An alternative to conventional chemotherapy can be utilization of monoclonal antibodies, which are proven to improve patient survival significantly as compared to conventional chemotherapy (Nivolumab + Ipilimumab, 2020).

AREA COVERED

Drug repurposing has been instrumental in drug discovery for rare diseases such as MPM and multiple repositioned small molecule therapies and immunotherapies are currently being tested for its applicability in MPM management. This article summarizes essential breakthroughs along the pre-clinical and clinical developmental stages of small molecules and monoclonal antibodies for MPM management.

EXPERT OPINION

For rare diseases such as malignant pleural mesothelioma, a drug repurposing strategy can be adapted as it eases the financial burden on pharmaceutical companies along with fast-tracking development. With the rise of multiple small molecule repurposed therapies and innovations in localized treatment, MPM therapeutics are bound to be more effective in this decade.

Targeting the FAK-Src Complex in Desmoplastic Small Round Cell Tumors, Ewing Sarcoma, and Rhabdomyosarcoma

Desmoplastic small round cell tumors (DSRCTs), Ewing sarcoma (ES), and alveolar and embryonal rhabdomyosarcoma (ARMS and ERMS) are malignant sarcomas typically occurring at young age, with a poor prognosis in the metastatic setting. New treatment options are necessary. Src family kinase inhibitor dasatinib single-agent treatment has been investigated in a phase 2 study in patients with advanced sarcomas including ES and RMS but failed as a single agent in these subtypes. Since previous studies demonstrated high FAK and Src activities in RMS and ES tissue and cell lines, and dasatinib treatment was shown to upregulate activated FAK, we hypothesized that FAK-Src combination treatment could potentially be an interesting treatment option for these tumor types. We examined the effects of targeting the FAK-Src complex by addressing (p)FAK and (p)Src expressions in tumor sections of DSRCT (n = 13), ES (n = 68), ARMS (n = 21), and ERMS (n = 39) and by determining the antitumor effects of single and combined treatment with FAK inhibitor defactinib and multikinase (Abl/SFK) inhibitor dasatinib in vitro on cell lines of each subtype. In vivo effects were assessed in DSRCT and ERMS models. Concurrent pFAK and pSrc expressions (H-score >50) were observed in DSRCT (67%), ES (6%), ARMS (35%), and ERMS (19%) samples. Defactinib treatment decreased pFAK expression and reduced cell viability in all subtypes. Dasatinib treatment decreased pSrc expression and cell viability in each subtype. Combination treatment led to a complete reduction in pFAK and pSrc in each cell line and showed enhanced cell viability reduction, drug synergy, DNA damage induction, and a trend toward higher apoptosis induction in DSRCT, ERMS, and ARMS but not in ES cells. These promising in vitro results unfortunately do not translate into promising in vivo results as we did not observe a significant effect on tumor volume in vivo, and the combination did not show superior effects compared to dasatinib single-agent treatment.

Focal adhesion kinase inhibitors, a heavy punch to cancer

Kinases are the ideal druggable targets for diseases and especially were highlighted on cancer therapy. Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase and its aberrant signaling extensively implicates in the progression of most cancer types, involving in cancer cell growth, adhesion, migration, and tumor microenvironment (TME) remodeling. FAK is commonly overexpressed and activated in a variety of cancers and plays as a targetable kinase in cancer therapy. FAK inhibitors already exhibited promising performance in preclinical and early-stage clinical trials. Moreover, substantial evidence has implied that targeting FAK is more effective in combination strategy, thereby reversing the failure of chemotherapies or targeted therapies in solid tumors. In the current review, we summarized the drug development progress, chemotherapy strategy, and perspective view for FAK inhibitors.

Focal Adhesion Kinase (FAK) Inhibition Synergizes with KRAS G12C Inhibitors in Treating Cancer through the Regulation of the FAK-YAP Signaling

KRAS mutation is one of the most prevalent genetic drivers of cancer development, yet KRAS mutations are until very recently considered undruggable. There are ongoing trials of drugs that target the KRAS G12C mutation, yet acquired drug resistance from the extended use has already become a major concern. Here, it is demonstrated that KRAS G12C inhibition induces sustained activation of focal adhesive kinase (FAK) and show that a combination therapy comprising KRAS G12C inhibition and a FAK inhibitor (IN10018) achieves synergistic anticancer effects. It can simultaneously reduce the extent of drug resistance. Diverse CDX and PDX models of KRAS G12C mutant cancer are examined and synergistic benefits from the combination therapy are consistently observed. Mechanistically, it is found that both aberrant FAK-YAP signaling and FAK-related fibrogenesis impact on the development of KRAS G12C inhibitor resistance. This study thus illustrates the mechanism of resistance of cancer to the treatment of KRAS G12C inhibitor, as well as an innovative combination therapy to improve treatment outcomes for KRAS G12C mutant cancers.

Radiosensitization by Kinase Inhibition Revealed by Phosphoproteomic Analysis of Pancreatic Cancer Cells

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive cancers and known for its extensive genetic heterogeneity, high therapeutic resistance, and strong variation in intrinsic radiosensitivity. To understand the molecular mechanisms underlying radioresistance, we screened the phenotypic response of 38 PDAC cell lines to ionizing radiation. Subsequent phosphoproteomic analysis of two representative sensitive and resistant lines led to the reproducible identification of 7,800 proteins and 13,000 phosphorylation sites (p-sites). Approximately 700 p-sites on 400 proteins showed abundance changes after radiation in all cell lines regardless of their phenotypic sensitivity. Apart from recapitulating known radiation response phosphorylation markers such as on proteins involved in DNA damage repair, the analysis uncovered many novel members of a radiation-responsive signaling network that was apparent only at the level of protein phosphorylation. These regulated p-sites were enriched in potential ATM substrates and in vitro kinase assays corroborated 10 of these. Comparing the proteomes and phosphoproteomes of radiosensitive and -resistant cells pointed to additional tractable radioresistance mechanisms involving apoptotic proteins. For instance, elevated NADPH quinine oxidoreductase 1 (NQO1) expression in radioresistant cells may aid in clearing harmful reactive oxygen species. Resistant cells also showed elevated phosphorylation levels of proteins involved in cytoskeleton organization including actin dynamics and focal adhesion kinase (FAK) activity and one resistant cell line showed a strong migration phenotype. Pharmacological inhibition of the kinases FAK by Defactinib and of CHEK1 by Rabusertib showed a statistically significant sensitization to radiation in radioresistant PDAC cells. Together, the presented data map a comprehensive molecular network of radiation-induced signaling, improves the understanding of radioresistance and provides avenues for developing radiotherapeutic strategies.

Inhibition of the mechanistic target of rapamycin induces cell survival via MAPK in tuberous sclerosis complex

Background

Tuberous sclerosis complex (TSC) is a genetic disorder that cause tumors to form in many organs. These lesions may lead to epilepsy, autism, developmental delay, renal, and pulmonary failure. Loss of function mutations in TSC1 and TSC2 genes by aberrant activation of the mechanistic target of rapamycin (mTORC1) signaling pathway are the known causes of TSC. Therefore, targeting mTORC1 becomes a most available therapeutic strategy for TSC. Although mTORC1 inhibitor rapamycin and Rapalogs have demonstrated exciting results in the recent clinical trials, however, tumors rebound and upon the discontinuation of the mTORC1 inhibition. Thus, understanding the underlying molecular mechanisms responsible for rapamycin-induced cell survival becomes an urgent need. Identification of additional molecular targets and development more effective remission-inducing therapeutic strategies are necessary for TSC patients.

Results

We have discovered an Mitogen-activated protein kinase (MAPK)-evoked positive feedback loop that dampens the efficacy of mTORC1 inhibition. Mechanistically, mTORC1 inhibition increased MEK1-dependent activation of MAPK in TSC-deficient cells. Pharmacological inhibition of MAPK abrogated this feedback loop activation. Importantly, the combinatorial inhibition of mTORC1 and MAPK induces the death of TSC2-deficient cells.

Conclusions

Our results provide a rationale for dual targeting of mTORC1 and MAPK pathways in TSC and other mTORC1 hyperactive neoplasm.

Protein Expression of Cyclin B1, Transferrin Receptor, and Fibronectin Is Correlated with the Prognosis of Adrenal Cortical Carcinoma

BACKGROUND

Adrenal cortical carcinoma (ACC) is a rare cancer with a variable prognosis. Several prognostic factors of ACC have been previously reported, but a proteomic analysis has not yet been performed. This study aimed to investigate prognostic biomarkers for ACC using a proteomic approach.

METHODS

We used reverse-phase protein array data from The Cancer Proteome Atlas, and identified differentially expressed proteins in metastatic ACCs. Multivariate Cox regression analysis adjusted by age and staging was used for survival analysis, and the C-index and category-free net reclassification improvement (cfNRI) were utilized to evaluate additive prognostic value.

RESULTS

In 46 patients with ACC, cyclin B1, transferrin receptor (TfR1), and fibronectin were significantly overexpressed in patients with distant metastasis. In multivariate models, high expression of cyclin B1 and TfR1 was significantly associated with mortality (hazard ratio [HR], 6.13; 95% confidence interval [CI], 1.02 to 36.7; and HR, 6.59; 95% CI, 1.14 to 38.2; respectively), whereas high fibronectin expression was not (HR, 3.92; 95% CI, 0.75 to 20.4). Combinations of high cyclin B1/high TfR1, high cyclin B1/high fibronectin, and high TfR1/high fibronectin were strongly associated with mortality ([HR, 13.72; 95% CI, 1.89 to 99.66], [HR, 9.22; 95% CI, 1.34 to 63.55], and [HR, 18.59; 95% CI, 2.54 to 135.88], respectively). In reclassification analyses, cyclin B1, TfR1, fibronectin, and combinations thereof improved the prognostic performance (C-index, 0.78 to 0.82-0.86; cfNRI, all P values <0.05).

CONCLUSION

In ACC patients, the overexpression of cyclin B1, TfR1, and fibronectin and combinations thereof were associated with poor prognosis.

Adipose‑derived mesenchymal stem cells ameliorate dibutyltin dichloride‑induced chronic pancreatitis by inhibiting the PI3K/AKT/mTOR signaling pathway

Adipose-derived mesenchymal stem cells (ASCs) play a positive role in tissue injury repair and regeneration. The aim of this study was to determine whether ASCs could ameliorate chronic pancreatitis (CP) induced by the injection of dibutyltin dichloride (DBTC) and to elucidate its potential mechanisms. Furthermore, this study also explored whether there was a significant difference if the ASCs were injected via the inferior vena cava or the left gastric artery. CP was induced in rats by a single intravenous administration of DBTC, and the accumulation of collagen and apoptotic rates of pancreatic acinar cells were analyzed. According to the results, ASCs markedly reduced DBTC-induced pancreatic damage and collagen deposition in the rat model of CP. Moreover, ASCs significantly decreased pancreatic cell apoptosis by regulating the expression levels of caspase-3, BAX and Bcl-2. These effects were observed regardless of whether the injection was in the inferior vena cava or the left gastric artery. It was also found that the expression levels of phosphorylated PI3K, AKT and mTOR in pancreatic tissues of the DBTC-induced CP model group were significantly increased, while the expression levels of phosphorylated PI3K, AKT and mTOR in the two treatment groups were markedly decreased. ASCs noticeably suppressed the PI3K/AKT/mTOR pathway in the pancreatic tissue of DBTC-induced CP. This study indicated that ASCs protect against pancreatic fibrosis by modulating the PI3K/AKT/mTOR pathway, and have the potential to be a new strategy for the treatment of CP in the future.

Phase 2 study of the focal adhesion kinase inhibitor defactinib (VS-6063) in previously treated advanced KRAS mutant non-small cell lung cancer

OBJECTIVES

KRAS mutations, which occur in approximately 25% of lung adenocarcinoma cases, represent a major unmet clinical need in thoracic oncology. Preclinical studies have demonstrated that KRAS mutant NSCLC cell lines and xenografts with additional alterations in either TP53 or CDKN2A (INK4A/ARF) loci are sensitive to focal adhesion kinase (FAK) inhibition. Defactinib (VS-6063) is a selective oral inhibitor of FAK.

MATERIALS AND METHODS

Patients with previously treated advanced KRAS mutant NSCLC were prospectively assigned to one of four molecularly defined cohorts based on the presence or absence of TP53 or CDKN2A alterations and received treatment with defactinib 400 mg orally BID until disease progression or intolerable toxicity. The primary endpoint was progression-free survival (PFS) at 12 weeks.

RESULTS

Fifty-five patients were enrolled. Mean age was 62 years; 51% were female. The median number of prior lines of therapy was 4 (range 1-8). Fifteen (28%) patients met the 12-week PFS endpoint, with one patient achieving a partial response. Median PFS was 45 days. Clinical efficacy did not correlate with TP53 or CDKN2A status. The most common adverse events were fatigue, gastrointestinal, and increased bilirubin, and were generally grade 1 or 2 in severity.

CONCLUSION

In heavily pretreated patients with KRAS mutant NSCLC, defactinib monotherapy demonstrated modest clinical activity. Efficacy was not associated with TP53 and CDKN2A status. Defactinib was generally well tolerated.

STK33 Promotes the Growth and Progression of Human Pancreatic Neuroendocrine Tumour via Activation of the PI3K/AKT/mTOR Pathway

BACKGROUND

Serine/threonine kinase 33 (STK33) has been reported to play an important role in cancer cell proliferation. We investigated the role of STK33 in pancreatic neuroendocrine tumour (PNET) and the underlying mechanisms.

METHODS

PNET specimens and adjacent non-tumorous pancreatic tissues from 84 patients who underwent curative surgery for PNET were stained by immunochemistry for STK33. The relationships among STK33 expression, clinicopathological parameters and clinical prognosis were statistically analysed. MTT, scratching, Transwell and apoptosis assays were employed to detect the effects of STK33 knockdown (siSTK33) or STK33 overexpression (pSTK33) on major oncogenic properties of cells of 2 PNET cell lines (BON and QGP-1), and real-time PCR and western blot were used to examine the expression of relevant genes.

RESULTS

Relative to its expression in normal pancreatic tissue, STK33 was overexpressed in PNET specimens. Furthermore, STK33 expression was significantly associated with World Health Organization classification (p < 0.001), American Joint Committee on Cancer stage (p < 0.001), lymph node metastasis (p < 0.001), tumour size (p = 0.022), sex (p = 0.003), perineural invasion (p < 0.001) and shorter disease-free survival of patients with PNET (p < 0.001). Enforced STK33 expression promoted PNET cell proliferation, migration and invasion and tumour growth and inhibited cell apoptosis, whereas STK33 depletion exerted the opposite effects. Mechanistic studies revealed that STK33 promoted growth and progression of PNET via activation of the phosphotidylinositol-3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway.

CONCLUSIONS

STK33 plays important roles in the tumour growth and progression of PNET via activation of the PI3K/AKT/mTOR pathway and has potential as a therapeutic target to improve PNET treatment.

PAK4-NAMPT Dual Inhibition as a Novel Strategy for Therapy Resistant Pancreatic Neuroendocrine Tumors

Pancreatic neuroendocrine tumors (PNET) remain an unmet clinical need. In this study, we show that targeting both nicotinamide phosphoribosyltransferase (NAMPT) and p21-activated kinase 4 (PAK4) could become a synthetic lethal strategy for PNET. The expression of PAK4 and NAMPT was found to be higher in PNET tissue compared to normal cells. PAK4-NAMPT dual RNAi suppressed proliferation of PNET cell lines. Treatment with KPT-9274 (currently in a Phase I trial or analogs, PF3758309 (the PAK4 selective inhibitor) or FK866 (the NAMPT inhibitor)) suppressed the growth of PNET cell lines and synergized with the mammalian target of rapamycin (mTOR) inhibitors everolimus and INK-128. Molecular analysis of the combination treatment showed down-regulation of known everolimus resistance drivers. KPT-9274 suppressed NAD pool and ATP levels in PNET cell lines. Metabolomic profiling showed a statistically significant alteration in cellular energetic pathways. KPT-9274 given orally at 150 mg/kg 5 days/week for 4 weeks dramatically reduced PNET sub-cutaneous tumor growth. Residual tumor analysis demonstrated target engagement in vivo and recapitulated in vitro results. Our investigations demonstrate that PAK4 and NAMPT are two viable therapeutic targets in the difficult to treat PNET that warrant further clinical investigation.

Phosphoproteome Analysis of Cells Infected with Adapted and Nonadapted Influenza A Virus Reveals Novel Pro- and Antiviral Signaling Networks

Influenza A viruses (IAVs) quickly adapt to new environments and are well known to cross species barriers. To reveal a molecular basis for these phenomena, we compared the Ser/Thr and Tyr phosphoproteomes of murine lung epithelial cells early and late after infection with mouse-adapted SC35M virus or its nonadapted SC35 counterpart. With this analysis we identified a large set of upregulated Ser/Thr phosphorylations common to both viral genotypes, while Tyr phosphorylations showed little overlap. Most of the proteins undergoing massive changes of phosphorylation in response to both viruses regulate chromatin structure, RNA metabolism, and cell adhesion, including a focal adhesion kinase (FAK)-regulated network mediating the regulation of actin dynamics. IAV also affected phosphorylation of activation loops of 37 protein kinases, including FAK and several phosphatases, many of which were not previously implicated in influenza virus infection. Inhibition of FAK proved its contribution to IAV infection. Novel phosphorylation sites were found on IAV-encoded proteins, and the functional analysis of selected phosphorylation sites showed that they either support (NA Ser178) or inhibit (PB1 Thr223) virus propagation. Together, these data allow novel insights into IAV-triggered regulatory phosphorylation circuits and signaling networks.IMPORTANCE Infection with IAVs leads to the induction of complex signaling cascades, which apparently serve two opposing functions. On the one hand, the virus highjacks cellular signaling cascades in order to support its propagation; on the other hand, the host cell triggers antiviral signaling networks. Here we focused on IAV-triggered phosphorylation events in a systematic fashion by deep sequencing of the phosphoproteomes. This study revealed a plethora of newly phosphorylated proteins. We also identified 37 protein kinases and a range of phosphatases that are activated or inactivated following IAV infection. Moreover, we identified new phosphorylation sites on IAV-encoded proteins. Some of these phosphorylations support the enzymatic function of viral components, while other phosphorylations are inhibitory, as exemplified by PB1 Thr223 modification. Our global characterization of IAV-triggered patterns of phospho-proteins provides a rich resource to further understand host responses to infection at the level of phosphorylation-dependent signaling networks.

An Institutional Experience of Tumor Progression to Pituitary Carcinoma in a 15-Year Cohort of 1055 Consecutive Pituitary Neuroendocrine Tumors

Pituitary carcinoma is a rare disease, defined by the presence of cerebrospinal or distant metastasis of a pituitary neuroendocrine tumor (PitNET). To review our institutional experience of pituitary carcinoma, we searched the database of the UHN Endocrine Oncology Site group and the University Health Network pathology laboratory information system from 2001 to 2016. Among 1055 PitNETs from 1169 transsphenoidal resections, we identified 4 cases of pituitary carcinoma, indicating that pituitary carcinoma represents around 0.4% of PitNETs. All four patients were women. The age at initial presentation ranged from 23 to 54 years. Two patients had Cushing disease with corticotroph tumors; one was initially a densely granulated corticotroph tumor that evolved to become sparsely granulated, while the other was a Crooke cell tumor. One patient had a functioning sparsely granulated lactotroph tumor and one had a clinically silent poorly differentiated PIT1 lineage tumor. Apart from a relatively high Ki67 labeling index (≥ 10%) in three tumors, there were no cytomorphologic features at the time of initial presentation that could predict subsequent metastatic behavior. The time from diagnosis of the pituitary neuroendocrine tumor to the diagnosis of malignancy was 3 to 14 years. Therapies included somatostatin analogs, external beam radiotherapy, chemotherapies including capecitabine/temozolomide, everolimus, sunitinib, bevacizumab, and peptide receptor radionuclide therapy (PRRT). One patient died of disease 18 years after initial diagnosis, underscoring the protracted course of this ultimately fatal neuroendocrine malignancy.

CDK4/6 inhibition stabilizes disease in patients with p16-null non-small cell lung cancer and is synergistic with mTOR inhibition

Aberrant activation of CDK4/6 kinase is the most common somatic event in non-small cell lung cancer (NSCLC). Palbociclib is a highly specific CDK4/6 inhibitor shown to inhibit cell cycle progression and promote cellular senescence. We conducted a phase 2 clinical trial of palbociclib in 19 previously-treated patients with advanced NSCLC. Only patients with p16-null staining by immunohistochemistry and documented tumor progression were eligible. The primary endpoint was tumor response rate. Palbociclib therapy alone was well-tolerated. Of 16 evaluable patients who received > 1 month of therapy, there were no objective responses. However, 8 patients (50%) with previously progressive NSCLC had stable disease (SD) lasting a range of 4-10.5 months. Median overall survival (OS) for all cases was 5.1 months, and median overall survival for the subset of patients with SD was 16.6 months. We also performed preclinical testing of palbociclib in combination with 13 different targeted or cytotoxic chemotherapeutic agents using a cell viability assay. Only the combination of palbociclib and mTOR inhibitors resulted in synergistic growth inhibition, particularly in tumors carrying RAS mutations. Our findings warrant further clinical investigation of the combination of palbociclib and mTOR inhibitors, especially in patients carrying activated RAS mutations.

Attenuation of everolimus-induced cytotoxicity by a protective autophagic pathway involving ERK activation in renal cell carcinoma cells

Aim

The mammalian target of rapamycin (mTOR) pathway is a critical target for cancer treatment and the mTOR inhibitor everolimus (RAD001) has been approved for treatment of renal cell carcinoma (RCC). However, the limited efficacy of RAD001 has led to the development of drug resistance. Autophagy is closely related to cell survival and death, which may be activated under RAD001 stimulation. The aim of the present study was to identify the underlying mechanisms of RAD001 resistance in RCC cells through cytoprotective autophagy involving activation of the extracellular signal-regulated kinase (ERK) pathway.

Methods and results:

RAD001 strongly induced autophagy of RCC cells in a dose- and time-dependent manner, as confirmed by Western blot analysis. Importantly, suppression of autophagy by the pharmacological inhibitor chloroquine effectively enhanced RAD001-induced apoptotic cytotoxicity, as demonstrated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and Western blot analysis, indicating a cytoprotective role for RAD001-induced autophagy. In addition, as was shown by the MTT assay, flow cytometry, and Western blot analysis, RAD001 robustly activated ERK, but not c-Jun N-terminal kinase and p38. Activation of ERK was inhibited by the pharmacological inhibitor selumetinib (AZD6244), which effectively promoted RAD001-induced cell death. Moreover, employing AZD6244 markedly attenuated RAD001-induced autophagy and enhanced RAD001-induced apoptosis, which play a central role in RAD001-induced cell death. Furthermore, RAD001-induced autophagy is regulated by ERK-mediated phosphorylation of Beclin-1 and B-cell lymphoma 2, as confirmed by Western blot analysis.

Conclusion

These results suggest that RAD001-induced autophagy involves activation of the ERK, which may impair cytotoxicity of RAD001 in RCC cells. Thus, inhibition of the activation of ERK pathway-mediated autophagy may be useful to overcome chemoresistance to RAD001.

Translational Diagnostics and Therapeutics in Pancreatic Neuroendocrine Tumors

Pancreatic neuroendocrine tumors (PNET) are rare tumors, but have been increasing in incidence. Although typically thought of as indolent, more than half of patients present with metastatic disease. For many years, the only mutations commonly known in these tumors were those in the MEN1 gene. Recently, the genetics underlying PNETs have been further defined through exome sequencing. The most frequent alterations found in sporadic PNETs are in MEN1, DAXX/ATRX, and a variety of genes in the mTOR pathway. Confirmation of these mutations has prompted trials with a number of drugs active in these pathways, and two drugs were eventually approved in 2011-sunitinib and everolimus. New data additionally identify the MET and CD47 receptors as potential novel drug targets. Yet despite improvements in progression-free survival with sunitinib and everolimus, further studies defining when to use these agents and factors associated with limitations in their utility are needed. As more discoveries are made in the laboratory that elucidate additional molecular mechanisms important in the initiation and metastasis of PNETs, continued efforts to translate these discoveries into distinct new therapies will be needed to improve patient survival. Clin Cancer Res; 22(20); 5022-9. ©2016 AACR SEE ALL ARTICLES IN THIS CCR FOCUS SECTION, "ENDOCRINE CANCERS REVISING PARADIGMS".

Targeted therapy of gastroenteropancreatic neuroendocrine tumours: preclinical strategies and future targets

Molecular targeted therapy of advanced neuroendocrine tumours (NETs) of the gastroenteropancreatic (GEP) system currently encompasses approved therapy with the mammalian target of rapamycin (mTOR) inhibitor everolimus and the multi-tyrosinkinase inhibitor sunitinib. However, clinical efficacy of these treatment strategies is limited by low objective response rates and limited progression-free survival due to tumour resistance. Further novel strategies for molecular targeted therapy of NETs of the GEP system are needed. This paper reviews preclinical research models and signalling pathways in NETs of the GEP system. Preclinical and early clinical data on putative novel targets for molecular targeted therapy of NETs of the GEP system are discussed, including PI3K, Akt, mTORC1/mTORC2, GSK3, c-Met, Ras-Raf-MEK-ERK, embryogenic pathways (Hedgehog, Notch, Wnt/beta-catenin, TGF-beta signalling and SMAD proteins), tumour suppressors and cell cycle regulators (p53, cyclin-dependent kinases (CDKs) CDK4/6, CDK inhibitor p27, retinoblastoma protein (Rb)), heat shock protein HSP90, Aurora kinase, Src kinase family, focal adhesion kinase and epigenetic modulation by histone deacetylase inhibitors.

Prognostic and predictive role of the PI3K-AKT-mTOR pathway in neuroendocrine neoplasms

Neuroendocrine neoplasms (NENs) are considered a heterogeneous and rare entity. Its natural history is influenced by multiple clinicopathological characteristics, which guide the management of these patients. The development of molecular biology reveals that the PI3K-AKT-mTOR pathway plays a relevant role in tumorigenesis and progression of NENs. Mammalian target of rapamycin (mTOR) inhibitors, targeted agents that block this pathway, has improved outcomes in neuroendocrine tumors (NETs). Different therapeutic approaches, such as somatostatin analogs, chemotherapy, peptide receptor radionuclide therapy, and targeted agents, have shown benefits in the treatment of NETs. However, there are not any established prognostic or predictive biomarkers to select the best therapy option to individualize treatment. Although a relation between alterations in the PI3K-AKT-mTOR pathway and clinical outcomes has not been found, these anomalies are considered attractive biomarkers. Additional molecular analysis should be integrated in future clinical trials' design to identify potential predictive or prognostic biomarkers.

Animal models of MEN1

Animal models of cancer have been instrumental in advancing our understanding of the biology of tumor initiation and progression, in studying gene function and in performing preclinical studies aimed at testing novel therapies. Several animal models of the MEN1 syndrome have been generated in different organisms by introducing loss-of-function mutations in the orthologues of the human MEN1 gene. In this review, we will discuss MEN1 and MEN1-like models in Drosophila, mice and rats. These model systems with their specific advantages and limitations have contributed to elucidate the function of Menin in tumorigenesis, which turned out to be remarkably conserved from flies to mammals, as well as the biology of the disease. Mouse models of MEN1 closely resemble the human disease in terms of tumor spectrum and associated hormonal changes, although individual tumor frequencies are variable. Rats affected by the MENX (MEN1-like) syndrome share some features with MEN1 patients albeit they bear a germline mutation in Cdkn1b (p27) and not in Men1 Both Men1-knockout mice and MENX rats have been exploited for therapy-response studies testing novel drugs for efficacy against neuroendocrine tumors (NETs) and have provided promising leads for novel therapies. In addition to presenting well-established models of MEN1, we also discuss potential models which, if implemented, might broaden even further our knowledge of neuroendocrine tumorigenesis. In the future, patient-derived xenografts in zebrafish or mice might allow us to expand the tool-box currently available for preclinical studies of MEN1-associated tumors.

The selective PI3Kα inhibitor BYL719 as a novel therapeutic option for neuroendocrine tumors: Results from multiple cell line models

Background/Aims

The therapeutic options for metastatic neuroendocrine tumors (NETs) are limited. As PI3K signaling is often activated in NETs, we have assessed the effects of selective PI3Kp110α inhibition by the novel agent BYL719 on cell viability, colony formation, apoptosis, cell cycle, signaling pathways, differentiation and secretion in pancreatic (BON-1, QGP-1) and pulmonary (H727) NET cell lines.

Methods

Cell viability was investigated by WST-1 assay, colony formation by clonogenic assay, apoptosis by caspase3/7 assay, the cell cycle by FACS, cell signaling by Western blot analysis, expression of chromogranin A and somatostatin receptors 1/2/5 by RT-qPCR, and chromogranin A secretion by ELISA.

Results

BYL719 dose-dependently decreased cell viability and colony formation with the highest sensitivity in BON-1, followed by H727, and lowest sensitivity in QGP-1 cells. BYL719 induced apoptosis and G0/G1 cell cycle arrest associated with increased p27 expression. Western blots showed inhibition of PI3K downstream targets to a varying degree in the different cell lines, but IGF1R activation. The most sensitive BON-1 cells displayed a significant, and H727 cells a non-significant, GSK3 inhibition after BYL719 treatment, but these effects do not appear to be mediated through the IGF1R. In contrast, the most resistant QGP-1 cells showed no GSK3 inhibition, but a modest activation, which would partially counteract the other anti-proliferative effects. Accordingly, BYL719 enhanced neuroendocrine differentiation with the strongest effect in BON-1, followed by H727 cells indicated by induction of chromogranin A and somatostatin receptor 1/2 mRNA-synthesis, but not in QGP-1 cells. In BON-1 and QGP-1 cells, the BYL719/everolimus combination was synergistic through simultaneous AKT/mTORC1 inhibition, and significantly increased somatostatin receptor 2 transcription compared to each drug separately.

Conclusion

Our results suggest that the agent BYL719 could be a novel therapeutic approach to the treatment of NETs that may sensitize NET cells to somatostatin analogs, and that if there is resistance to its action this may be overcome by combination with everolimus.

Fibronectin: How Its Aberrant Expression in Tumors May Improve Therapeutic Targeting

Fibronectin is a matrix glycoprotein which has not only been found to be over-expressed in several cancers, but has been shown to participate in several steps of tumorigenesis. The purpose of this review is to illustrate how aberrant fibronectin expression influences tumor growth, invasion, metastasis and therapy resistance. In particular, this review will focus on the interactions between cell receptor ligands and fibronectin and how this interaction influences downstream signaling events that aid tumor progression. This review will further discuss the possible implications of therapeutic drugs directed against fibronectin and/or cellular interactions with fibronectin and will additionally discuss novel approaches by which to limit intra- and extra-tumoral fibronectin expression and the cellular events which lead to aberrant fibronectin expression. It is anticipated that these studies will set a basis for future research that will not only aid understanding of fibronectin and its prognostic significance, but will further elucidate novel targets for therapeutics.

Pancreatic Neuroendocrine Tumors and EMT Behavior Are Driven by the CSC Marker DCLK1

Doublecortin-like kinase 1 (DCLK1), a marker for intestinal and pancreatic cancer stem cells, is highly expressed in neuroblastomas. This study was conducted to assess DCLK1 expression levels in pancreatic neuroendocrine tumor (PNET) tissues and to explore the roles of this molecule in clinical tissue from multiple PNET patients, cells (BON1, QGP1, and CM) and tumor xenografts. Immunohistochemically, all PNET tissues highly and diffusely expressed DCLK1 as a full-length isoform, identical to that detected in primary liver NETs. A DCLK1-overexpressing PNET cell line (QGP1-DCLK1) exhibited epithelial-mesenchymal transition (EMT)-related gene signatures, and robust upregulation of Slug (SNAI2), N-Cadherin (CDH2), and Vimentin (VIM) was validated by real-time PCR and immunoblotting. QGP1-DCLK1 cells had increased cell migration in a wound-healing assay and formed significantly larger xenograft tumors in nude mice. The factors involved in the formation of the fast-growing tumors included p-FAK (on Tyr925), p-ERK1/2, p-AKT, Paxillin, and Cyclin D1, which upon knockdown or pharmacologic inhibition of DCLK1 abolished the expression of these molecules. In conclusion, robust and ubiquitous expression of DCLK1 was first demonstrated here in human PNET tissue specimens and cells. DCLK1 characterized the PNET cell behavior, inducing p-FAK/SLUG-mediated EMT. These findings suggest the possibility of developing novel therapeutic strategies against PNETs by targeting DCLK1.Implications: Evidence here reveals that human PNETs diffusely and robustly express the cancer stem cell marker DCLK1, which drives SLUG-mediated EMT, and suggests that NETs share biological features for druggable targets with other tumors, including neuroblastoma that also highly expresses DCLK1. Mol Cancer Res; 15(6); 744-52. ©2017 AACR.

WOMEN IN CANCER THEMATIC REVIEW: Systemic therapies in neuroendocrine tumors and novel approaches toward personalized medicine

Neuroendocrine tumors (NETs) are a group of heterogenous neoplasms. Evidence-based treatment options for antiproliferative therapy include somatostatin analogues, the mTOR inhibitor everolimus, the multiple tyrosine kinase inhibitor sunitinib and peptide receptor radionuclide therapy with 177-Lu-octreotate. In the absence of definite predictive markers, therapeutic decision making follows clinical and pathological criteria. As objective response rates with targeted drugs are rather low, and response duration is limited in most patients, numerous combination therapies targeting multiple pathways have been explored in the field. Upfront combination of drugs, however, is associated with increasing toxicity and has shown little benefit. Major advancements in the molecular understanding of NET based on genomic, epigenomic and transcriptomic analysis have been achieved with prognostic and therapeutic impact. New insight into molecular alterations has paved the way to biomarker-driven clinical trials and may facilitate treatment stratification toward personalized medicine in the near future. However, an improved understanding of the complexity of pathway interactions is required for successful treatment. A systems biology approach is one of the tools that may help to achieve this endeavor.

Digestive neuroendocrine neoplasms: A 2016 overview

Digestive neuroendocrine neoplasms (DNENs) have an incidence of 2.39 per 100,000 inhabitants per year, and a prevalence of 35 cases per 100,000; the gap between these rates is to be referred to the relatively long survival that characterizes the majority of these tumors, which can be thus considered as chronic oncological diseases. Up to 80% of patients are stage IV since the first diagnosis, presenting a 5-yr overall survival rate of 35%-55% and a twice higher mortality than limited disease. DNENs express somatostatin receptors in more than 80% of cases, detected through immunohistochemistry or functional imaging tests (FITs). This feature identifies patients who may benefit from "cold" somatostatin analogs (SSAs) or peptide receptors radionuclide therapy, although SSAs are sometimes used also with a negative uptake at FITs. The therapeutic options have been recently increased after the identification of molecular pathways involved in DNENs pathogenesis, and the subsequent use of targeted therapies (i.e., Everolimus and Sunitinib) for these neoplasms. This review offers an overview about pancreatic and small bowel NENs, critically underlining the issues that still need to be clarified and the future perspectives to be investigated.

Targeting focal adhesion kinase renders pancreatic cancers responsive to checkpoint immunotherapy

Single-agent immunotherapy has achieved limited clinical benefit to date in patients suffering from pancreatic ductal adenocarcinoma (PDAC). This may be due to the presence of a uniquely immunosuppressive tumor microenvironment (TME). Critical obstacles to immunotherapy in PDAC tumors include a high number of tumor-associated immunosuppressive cells and a uniquely desmoplastic stroma that acts as a barrier to T-cell infiltration. We have identified hyperactivated focal adhesion kinase (FAK) activity in neoplastic PDAC cells as a significant regulator of the fibrotic and immunosuppressive TME. We found that FAK activity was elevated in human PDAC tissues and correlates with high levels of fibrosis and poor CD8⁺ cytotoxic T-cell infiltration. Single-agent FAK inhibition using the selective FAK inhibitor VS-4718 significantly limited tumor progression, resulting in a doubling of survival in the p48-Cre/LSL-Kras^G12D/p53^Flox/+ (KPC) mouse model of human PDAC. This delay in tumor progression was associated with dramatically reduced tumor fibrosis, and decreased numbers of tumor-infiltrating immunosuppressive cells. We also found that FAK inhibition rendered the previously unresponsive KPC mouse model responsive to T cell immunotherapy and PD-1 antagonists. These data suggest that FAK inhibition increases immune surveillance by overcoming the fibrotic and immunosuppressive PDAC TME and renders tumors responsive to immunotherapy.

Synergism between the mTOR inhibitor rapamycin and FAK down-regulation in the treatment of acute lymphoblastic leukemia

Background

Acute lymphoblastic leukemia (ALL) is an aggressive malignant disorder of lymphoid progenitor cells in both children and adults. Although improvements in contemporary therapy and development of new treatment strategies have led to dramatic increases in the cure rate in children with ALL, the relapse rate remains high and the prognosis of relapsed childhood ALL is poor. Molecularly targeted therapies have emerged as the leading treatments in cancer therapy. Multi-cytotoxic drug regimens have achieved success, yet many studies addressing targeted therapies have focused on only one single agent. In this study, we attempted to investigate whether the effect of the mammalian target of rapamycin (mTOR) inhibitor rapamycin is synergistic with the effect of focal adhesion kinase (FAK) down-regulation in the treatment of ALL.

Methods

The effect of rapamycin combined with FAK down-regulation on cell proliferation, the cell cycle, and apoptosis was investigated in the human precursor B acute lymphoblastic leukemia cells REH and on survival time and leukemia progression in a non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mouse model.

Results

When combined with FAK down-regulation, rapamycin-induced suppression of cell proliferation, G₀/G₁ cell cycle arrest, and apoptosis were significantly enhanced. In addition, REH cell-injected NOD/SCID mice treated with rapamycin and a short-hairpin RNA (shRNA) to down-regulate FAK had significantly longer survival times and slower leukemia progression compared with mice injected with REH-empty vector cells and treated with rapamycin. Moreover, the B-cell CLL/lymphoma-2 (BCL-2) gene family was shown to be involved in the enhancement, by combined treatment, of REH cell apoptosis.

Conclusions

FAK down-regulation enhanced the in vitro and in vivo inhibitory effects of rapamycin on REH cell growth, indicating that the simultaneous targeting of mTOR- and FAK-related pathways might offer a novel and powerful strategy for treating ALL.