Validation of mammalian target of rapamycin biomarker panel in patients with clear cell renal cell carcinoma

Retrospective immunophenotypical evaluation of MET, PD-1/PD-L1, and mTOR pathways in primary tumors and pulmonary metastases of renal cell carcinoma: the RIVELATOR study addresses the issue of biomarkers heterogeneity

Aim

In renal cell carcinoma (RCC), tumor heterogeneity generated challenges to biomarker development and therapeutic management, often becoming responsible for primary and acquired drug resistance. This study aimed to assess the inter-tumoral, intra-tumoral, and intra-lesional heterogeneity of known druggable targets in metastatic RCC (mRCC).

Methods

The RIVELATOR study was a monocenter retrospective analysis of biological samples from 25 cases of primary RCC and their paired pulmonary metastases. The biomarkers analyzed included MET, mTOR, PD-1/PD-L1 pathways and the immune context.

Results

High multi-level heterogeneity was demonstrated. MET was the most reliable biomarker, with the lowest intratumor heterogeneity: the positive mutual correlation between MET expression in primary tumors and their metastases had a significantly proportional intensity (P = 0.038). The intratumor heterogeneity grade was significantly higher for the mTOR pathway proteins. Combined immunophenotypical expression patterns and their correlations with the immune context were uncovered [i.e., mTOR expression in the metastases positively correlated with PD-L1 expression in tumor-infiltrating lymphocytes (TILs), P = 0.019; MET expression was related to PD-1 expression on TILs (P = 0.041, ρ = 0.41) and peritumoral lymphocytes (RILs; P = 0.013, ρ = 0.49)], suggesting the possibility of predicting drug response or resistance to tyrosine kinase, mTOR, or immune checkpoint inhibitors.

Conclusions

In mRCC, multiple and multi-level assays of potentially predictive biomarkers are needed for their reliable translation into clinical practice. The easy-to-use immunohistochemical method of the present study allowed the identification of different combined expression patterns, providing cues for planning the management of systemic treatment combinations and sequences in an mRCC patient population. The quantitative heterogeneity of the investigated biomarkers suggests that multiple intralesional assays are needed to consider the assessment reliable for clinical considerations.

Significance of PI3K signalling pathway in clear cell renal cell carcinoma in relation to VHL and HIF status

Renal cell carcinoma (RCC) includes diverse tumour types characterised by various genetic abnormalities. The genetic changes, like mutations, deletions and epigenetic alterations, play a crucial role in the modification of signalling networks, tumour pathogenesis and prognosis. The most prevalent RCC type, clear cell RCC (ccRCC), is asymptomatic in the early stages and has a poorer prognosis compared with the papillary and the chromophobe types RCCs. Generally, ccRCC is refractory to chemotherapy and radiation therapy. Loss of von Hippel-Lindau (VHL) gene and upregulation of hypoxia-inducible factors (HIF), the signature of most sporadic ccRCC, promote multiple growth factors. Hence, VHL/HIF and a variety of pathways, including phosphatase and TEnsin homolog on chromosome 10/phosphatidylinositol-3-kinase (PI3K)/AKT, are closely connected and contribute to the ontogeny of ccRCC. In the recent decade, multiple targeting agents have been developed based on blocking major signalling pathways directly or indirectly involved in ccRCC tumour progression, metastasis, angiogenesis and survival. However, most of these drugs have limitations; either metastatic ccRCC develops resistance to these agents, or despite blocking receptors, tumour cells use alternate signalling pathways. This review compiles the state of knowledge about the PI3K/AKT signalling pathway confined to ccRCC and its cross-talks with VHL/HIF pathway.

Characterization of the expression of LAT1 as a prognostic indicator and a therapeutic target in renal cell carcinoma

Large neutral amino acid transporter 1 (LAT1, SLC7A5) is abundantly expressed in various types of cancer, and it has been thought to assist cancer progression through its activity for uptake of neutral amino acids. However, the roles of LAT1 in renal cell carcinoma (RCC) prognosis and treatment remain uncharacterized. Therefore, we first retrospectively examined the LAT1 expression profile and its associations with clinical factors in RCC tissues (n = 92). The results of immunohistochemistry showed that most of the tissues examined (92%) had cancer-associated LAT1 expression. Furthermore, the overall survival (OS) and progression-free survival (PFS) were shorter in patients with high LAT1 expression levels than in those with low LAT1 expression levels (P = 0.018 and 0.014, respectively), and these associations were further strengthened by the results of univariate and multivariate analyses. Next, we tested the effects of JPH203, which is a selective LAT1 inhibitor, on RCC-derived Caki-1 and ACHN cells. It was found that JPH203 inhibited the growth of these cell types in a dose-dependent manner. Moreover, JPH203 clearly suppressed their migration and invasion activities. Thus, our results show that LAT1 has a great potential to become not only a prognosis biomarker but also a therapeutic target in RCC clinical settings.

The Prognostic Role of Ribosomal Protein S6 Kinase 1 Pathway in Patients With Solid Tumors: A Meta-Analysis

Background: Recent studies supported the predictive role of ribosomal protein S6 kinase 1 (S6K1), phosphorylated S6K1 (p-S6K1), and phosphorylated ribosomal protein S6 (p-S6) for the outcome of cancer patients. However, inconsistent results were acquired across different researches. To comprehensively and quantitatively elucidate their prognostic significance in solid malignancies, the current meta-analysis was carried out utilizing the results of clinical studies.

Methods: We conducted the literature retrieval by searching PubMed, Web of Science, EMBASE, and Cochrane library to identify eligible publications. Data were collected from included articles to calculate pooled overall survival (OS), disease-free survival (DFS), recurrence-free survival (RFS), and progression-free survival (PFS). Hazard ratios (HRs) with 95% confidence intervals (CIs) served as appropriate parameters to assess prognostic significance.

Results: Forty-four original studies were included, of which 7 studies were analyzed for S6K1, 24 for p-S6K1, and 16 for p-S6. The overexpression of p-S6K1 was significantly associated with poorer prognosis of solid tumor patients in OS (HR = 1.706, 95%CI: 1.369–2.125, p < 0.001), DFS (HR = 1.665, 95%CI: 1.002–2.768, p = 0.049). However, prognostic role of p-S6K1 in RFS and PFS was not found. The result also revealed that S6K1 and p-S6 were significantly associated with reduced OS (HR = 1.691, 95%CI: 1.306–2.189, p < 0.001; HR = 2.019, 95%CI: 1.775–2.296, p < 0.001, respectively).

Conclusions: The present meta-analysis demonstrated that elevated expression of S6K1, p-S6K1, or p-S6 might indicate worse prognosis of patients with solid tumors, and supported a promising clinical test to predict solid tumor prognosis based on the level of S6K1 pathway.

A three-molecule score based on Notch pathway predicts poor prognosis in non-metastasis clear cell renal cell carcinoma

We constructed a three-molecule score based on the expression of Notch pathway molecules: Jagged1, intracellular Notch1 (ICN1) and Hes1 (JIH score). To assess prognostic value of the JIH score in non-metastasis clear cell renal cell carcinoma (ccRCC), we identified 467 patients who underwent nephrectomy during 2008-2009 as our study population. Immunohistochemistry was used to evaluate the expression of these three molecules. Cox regression models were applied to construct the JIH score, while Kaplan-Meier methods, multivariate analyses and nomogram were used to explore prognostic value of the JIH score. Our result confirmed that JIH score was an independent prognosticator for both overall survival (OS) and recurrence-free survival (RFS). Survival analyses showed that a higher JIH score indicated worse clinical outcomes (JIH score 3: 58.3% and 58.0% for 6-year OS and RFS, respectively; JIH score 0: 96.7% and 91.6% for 6-year OS and RFS, respectively). Nomograms based on JIH score and other conventional clinicopathological features had a better capability in predicting patients with pT1 stage disease for both OS and RFS (84.6% and 83.9%, respectively). The JIH score is a novel prognosticator representing activation of Notch pathway for non-metastasis ccRCC, and raises an alternative strategy for excavating potential biomarkers for signal pathways.

Expression of micro-RNAs and genes related to angiogenesis in ccRCC and associations with tumor characteristics

BACKGROUND

Clear cell renal cell carcinoma (ccRCC) is the third most common urological cancer in adults. Our aim is to evaluate genes and miRNAs expression profiles involved with angiogenesis and tumor characteristics in ccRCC.

METHODS

The expression levels of miRNAs miR-99a, 99b, 100; 199a; 106a; 106b; 29a; 29b; 29c; 126; 200a, 200b and their respective target genes: mTOR, HIF1-α, VHL, PDGF, VEGF, VEGFR1 and VEGFR2 were analyzed using qRT-PCR in tumor tissue samples from 56 patients with ccRCC. Five samples of benign renal tissue were utilized as control. The expression levels of miRNAs and genes were related to tumor size, Fuhrman nuclear grade and microvascular invasion.

RESULTS

miR99a was overexpressed in most samples and its target gene mTOR was underexpressed, this also occurs for miRNAs 106a, 106b, and their target gene VHL. An increase in miR-200b was correlated with high-risk tumors (p = 0.01) while miR-126 overexpression was associated with Fuhrman's low grade (p = 0.03).

CONCLUSIONS

Our results show that in ccRCC there are changes in miRNAs expression affecting gene expression that could be important in determining the aggressiveness of this lethal neoplasia.

Resistance to Targeted Therapies in Renal Cancer: The Importance of Changing the Mechanism of Action

Renal cell carcinoma (RCC) is a complex disease characterized by mutations in several genes. Loss of function of the von Hippel-Lindau (VHL) tumour suppressor gene is a very common finding in RCC and leads to up-regulation of hypoxia-inducible factor (HIF)-responsive genes accountable for angiogenesis and cell growth, such as platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF). Binding of these proteins to their cognate tyrosine kinase receptors on endothelial cells promotes angiogenesis. Promotion of angiogenesis is in part due to the activation of the phosphatidylinositol-3-kinase (PI3K)/AKT/mechanistic target of rapamycin (mTOR) pathway. Inhibition of this pathway decreases protein translation and inhibits both angiogenesis and tumour cell proliferation. Although tyrosine kinase inhibitors (TKIs) stand as the main first-line treatment option for advanced RCC, eventually all patients will become resistant to TKIs. Resistance can be overcome by using second-line treatments with different mechanisms of action, such as inhibitors of mTOR, c-MET, programmed death 1 (PD-1) receptor, or the combination of an mTOR inhibitor (mTORi) with a TKI. In this article, we briefly review current evidence regarding mechanisms of resistance in RCC and treatment strategies to overcome resistance with a special focus on the PI3K/AKT/mTOR pathway.

Prognostic value of tissue-based biomarker signature in clear cell renal cell carcinoma

OBJECTIVE

To improve risk stratification for recurrence prognostication in patients with localised clear cell renal cell carcinoma (ccRCC).

PATIENTS AND METHODS

In all, 367 patients with non-metastatic ccRCC were included. The cohort was divided into a training and validation set. Using tissue microarrays, immunostaining was performed for 24 biomarkers representative of key pathways in ccRCC. Using Least Absolute Shrinkage and Selection Operator (LASSO) Cox regression, we identified several markers that were used to construct a risk classifier for risk of disease recurrence.

RESULTS

The median (interquartile range) follow-up was 63.5 (24.0-85.3) months. Five out of 24 markers were selected by LASSO Cox regression for the risk classifier: N-cadherin, E-cadherin, Ki67, cyclin D1 and phosphorylated eukaryotic initiation factor 4E binding protein-1 (p-4EBP1). Patients were classified as either low, intermediate or high risk of disease recurrence by tertiles of risk score. The 5-year recurrence-free survival (RFS) was 93.8%, 87.7% and 70% for patients with low-, intermediate- and high-risk scores, respectively (P < 0.001). Patients with a high marker score had worse RFS on multivariate analysis adjusted for age, gender, race and the Mayo Clinic Stage, Size, Grade, and Necrosis (SSIGN) score (hazard ratio 3.66, 95% confidence interval 1.58-8.49, P = 0.003 for high vs low marker score in the overall cohort). The five-marker classifier increased the concordance index of the clinical model in both the training and validation sets.

CONCLUSION

We developed a five-marker-based prognostic tool that can effectively classify patients with ccRCC according to risk of disease recurrence after surgery. This tool, if prospectively validated, could provide individualised risk estimation for patients with ccRCC.

Immunohistochemical evaluation of the mTOR pathway in intra-oral minor salivary gland neoplasms

OBJECTIVES

The aim of this study was to investigate the expression of upstream and downstream molecules of the oncogenic mTOR signaling pathway in intra-oral minor salivary gland tumors (SGTs).

MATERIALS AND METHODS

Tissue samples consisted of 39 malignant and 13 benign minor SGTs, and 8 controls of normal minor salivary glands (NMSG). An immunohistochemical analysis for phosphorylated Akt, 4EBP1 and S6 (total and phosphorylated), and eIF4E was performed.

RESULTS

Expression of pAkt and 4EBP1 was observed in all SGTs and in most NMSG. p4EBP1 was detected in almost all SGT cases, NMSG being negative. S6 immunoreactivity was observed in 37.5% of NMSG, 92.3% of benign and 100% of malignant SGTs, while pS6 expression was observed in 77% of benign and 95% of malignant SGTs, but not in NMSG. Finally, eIF4E was expressed in 12.5% of NMSG, 69.2% of benign, and 76.9% of malignant tumors. All molecules studied had statistically significantly lower expression in NMSG compared with SGTs. Moreover, malignant neoplasms received higher scores compared with benign tumors for all molecules with the exception of eIF4E.

CONCLUSION

The mTOR signaling pathway is activated in SGTs, especially in malignancies. Therefore, the possible therapeutic role of targeting the mTOR pathway by rapamycin analogs in SGTs needs further investigation.

Postoperative surveillance imaging for patients undergoing nephrectomy for renal cell carcinoma

The American Urological Association and the National Comprehensive Cancer Network guidelines regarding postoperative surveillance for renal cell carcinoma (RCC) have provided a standardized framework for imaging following nephrectomy. These stage-stratified recommendations are based on retrospective studies that identified the timeline and location of RCC recurrences. However, the simplified and generalizable protocols offered by the American Urological Association and the National Comprehensive Cancer Network are not without limitations. Studies have found that RCC recurrences continue to be missed even with perfect compliance to these protocols and that RCC recurrences occur not infrequently after the required surveillance window of 5 years. Furthermore, recent studies evaluating the use of adjuvant systemic therapy in patients who are at a high risk for RCC recurrence or metastasis after nephrectomy have yielded disappointing results. This calls into question what interventions we can offer patients to improve survival once RCC recurrences are detected during postoperative surveillance; an effective surveillance strategy requires effective treatment options. The future of personalized medicine with genetic profiling of patients with RCC may offer a potential solution by providing better risk stratification to determine the intensity of surveillance imaging as well as to determine which patients will actually derive survival benefit from intervention on recurrent disease.

Oncogenes strike a balance between cellular growth and homeostasis

Altered tumor cell metabolism is now firmly established as a hallmark of human cancer. Downstream of oncogenic events, metabolism is re-wired to support cellular energetics and supply the building blocks for biomass. Rapid, uncontrolled proliferation results in tumor growth beyond the reach of existing vasculature and triggers cellular adaptations to overcome limiting nutrient and oxygen delivery. However, oncogenic activation and metabolic re-programming also elicit cell intrinsic stresses, independent of the tumor microenvironment. To ensure metabolic robustness and stress resistance, pro-growth signals downstream of oncogene activation or tumor suppressor loss simultaneously activate homeostatic processes. Here, we summarize recent literature describing the adaptive mechanisms co-opted by common oncogenes, including mTOR, MYC, and RAS. Recurrent themes in our review include: (1) coordination of oncogene-induced changes in protein and lipid metabolism to sustain endoplasmic reticulum homeostasis, (2) maintenance of mitochondrial functional capacity to support anabolic metabolism, (3) adaptations to sustain intracellular metabolite concentrations required for growth, and (4) prevention of oxidative stress. We also include a discussion of the hypoxia inducible factors (HIFs) and the AMP-dependent protein kinase (AMPK)--stress sensors that are co-opted to support tumor growth. Ultimately, an understanding of the adaptations required downstream of specific oncogenes could reveal targetable metabolic vulnerabilities.

Tumour and patient factors in renal cell carcinoma-towards personalized therapy

Renal cell carcinoma (RCC) comprises a heterogeneous group of histologically and molecularly distinct tumour subtypes. Current targeted therapies have improved survival in patients with advanced disease but complete response occurs rarely, if at all. The genomic characterization of RCC is central to the development of novel targeted therapies. Large-scale studies employing multiple 'omics' platforms have led to the identification of key driver genes and commonly altered pathways. Specific molecular alterations and signatures that correlate with tumour phenotype and clinical outcome have been identified and can be harnessed for patient management and counselling. RCC seems to be a remarkably diverse malignancy with significant intratumour and intertumour genetic heterogeneity. The tumour microenvironment is increasingly recognized as a vital regulator of RCC tumour biology. Patient factors, including immune response and drug metabolism, vary widely, which can lead to widely divergent responses to drug therapy. Intratumour heterogeneity poses a significant challenge to the development of personalized therapies in RCC as a single biopsy might not accurately represent the clonal population ultimately responsible for aggressive biologic behaviour. On the other hand, the diversity of genomic alterations in RCC could also afford opportunities for targeting unique pathways based on analysis of an individual tumour's molecular composition.

HIF2α-Dependent Lipid Storage Promotes Endoplasmic Reticulum Homeostasis in Clear-Cell Renal Cell Carcinoma

Two hallmarks of clear-cell renal cell carcinoma (ccRCC) are constitutive hypoxia-inducible factor (HIF) signaling and abundant intracellular lipid droplets (LD). However, regulation of lipid storage and its role in ccRCC are incompletely understood. Transcriptional profiling of primary ccRCC samples revealed that expression of the LD coat protein gene PLIN2 was elevated in tumors and correlated with HIF2α, but not HIF1α, activation. HIF2α-dependent PLIN2 expression promoted lipid storage, proliferation, and viability in xenograft tumors. Mechanistically, lipid storage maintained integrity of the endoplasmic reticulum (ER), which is functionally and physically associated with LDs. Specifically, PLIN2-dependent lipid storage suppressed cytotoxic ER stress responses that otherwise result from elevated protein synthetic activity characteristic of ccRCC cells. Thus, in addition to promoting ccRCC proliferation and anabolic metabolism, HIF2α modulates lipid storage to sustain ER homeostasis, particularly under conditions of nutrient and oxygen limitation, thereby promoting tumor cell survival.

SIGNIFICANCE

We demonstrate that HIF2α promotes lipid storage, ER homeostasis, and cell viability in ccRCC via upregulation of the LD coat protein PLIN2, revealing a novel function for the well-documented "clear-cell" phenotype and identifying ER stress as a targetable vulnerability created by HIF2α/PLIN2 suppression in this common renal malignancy.