Cell heterogeneity in clear cell renal cell carcinoma

METTL14-mediated N6-methyladenosine modification of Pten mRNA inhibits tumour progression in clear-cell renal cell carcinoma

BACKGROUND

Clear-cell renal-cell carcinoma (ccRCC) is one of the leading causes of tumour-related death worldwide. Methyltransferase-like 14 (METTL14) is reported to regulate m6A modification in cancers. The aim of this study is to investigate the biological function and molecular mechanism of METTL14 in the pathogenesis of ccRCC.

METHODS

Quantitative real-time PCR (qRT-PCR), western blot and immunohistochemical (IHC) assays were used to detect the expression of METTL14 and Pten. METTL14 overexpression or knockdown was used in the in vitro and in vivo studies to investigate the biological functions of METTL14. m6A-RNA immunoprecipitation and RNA immunoprecipitation were used to investigate the m6A modification mediated by METTL14.

RESULTS

METTL14 expression was significantly down-regulated in ccRCC tissues. Functionally, upregulation of METTL14 inhibited ccRCC cells proliferation and migration in vitro. METTL14 overexpression significantly inhibited the activation of the phosphoinositide 3 kinase (PI3K)/AKT signalling pathway. Furthermore, phosphate and tension homology deleted on chromosome ten (Pten) is a target of METTL14. Overexpression of METTL14 increased the m6A enrichment of Pten, and promoted Pten expression. METTL14-enhanced Pten mRNA stability was dependent on YTHDF1.

CONCLUSIONS

METTL14-mediated m6A modification of Pten mRNA inhibited tumour progression, suggesting that METTL14 might be a potential prognostic biomarker and effective therapeutic target for ccRCC.

Potential impact of PD-L1 (SP-142) immunohistochemical heterogeneity in clear cell renal cell carcinoma immunotherapy

Intratumor heterogeneity (ITH) detection remains a challenge in modern oncology because it can have a direct impact on the success of new therapies. Anti-PD-1/PD-L1 immunotherapy is an emerging treatment modality that is showing great promise for clear cell renal cell carcinoma (CCRCC) patients with advanced disease. Patient selection for such therapy relies upon the immunohistochemical detection of PD-1/PD-L1, however the degree of ITH for these markers among tumor cells and/or inflammatory mononuclear infiltrates remains unknown. Therefore, we analyzed PD-L1 (SP-142) expression in the tumor inflammatory cells of 22 CCRCC cases with the aim to define the pattern of PD-L1 expression, and to compare the reliability of current tumor sampling protocols (RS) with a multisite tumor sampling strategy (MSTS). While the RS protocol identified 5/22 (22.7%) of cases that were positive for PD-L1 expression, MSTS identified 10/22 (45.45%) of cases. This suggests that RS may miss a proportion of CCRCC patients that might benefit from immunotherapy. In addition, MSTS demonstrated that positive and negative regions of PD-L1 expression are very variable within each tumor.

Pathological Bases and Clinical Impact of Intratumor Heterogeneity in Clear Cell Renal Cell Carcinoma

PURPOSE OF REVIEW

Intratumor heterogeneity is an inherent event in tumor development that is receiving much attention in the last years since it is responsible for most failures of current targeted therapies. The purpose of this review is to offer clinicians an updated insight of the multiple manifestations of a complex event that impacts significantly patient's life.

RECENT FINDINGS

Clear cell renal cell carcinoma is the most common renal tumor and a paradigmatic example of a heterogeneous neoplasm. Next-generation sequencing has demonstrated that intratumor heterogeneity encompasses genetic, epigenetic, and microenvironmental variability. Currently accepted protocols of tumor sampling seem insufficient in unveiling intratumor heterogeneity with reliability and need to be updated. This variability challenges the precise morphological diagnosis, its molecular characterization, and the selection of optimal personalized therapies in clear cell renal cell carcinoma, a neoplasm traditionally considered chemo- and radio-resistant. We review the state of the art of the different approaches to intratumor heterogeneity in clear cell renal cell carcinomas, from the simple morphology to the most sophisticated massive sequencing tools.

High levels of intratumor heterogeneity characterize the expression of epithelial-mesenchymal transition markers in high-grade clear cell renal cell carcinoma

Immunohistochemistry is a basic routine in establishing the diagnosis of many tumors. However, immunomarkers are often irregularly distributed across different regions of the same tumor, alternating positive and negative areas without any apparent cause. Full identification of this type of intratumor heterogeneity is crucial for patients since the expression of many markers is linked to the prognosis and/or treatment of some tumors. We have quantified this variability testing 406 tumor samples from eight clear cell renal cell carcinomas using four epithelial-mesenchymal transition markers (vimentin, ZEB-1, β-catenin, and E-cadherin) and two different sampling protocols. Routine sampling included an amount of 59 samples (average, 7.3 samples/case) and multisite tumor sampling did a total of 347 samples (average, 43.3 samples/case). High variability of immunostaining was detected with E-cadherin and ZEB-1 in all high-grade cases. Irregular patterns of expression were detected in all tumors including all histologically homogeneous low-grade tumors. Multisite tumor sampling protocol detected a significant decreased number of E-cadherin, β-catenin and ZEB-1 positive samples in high-grade tumors. We conclude that high levels of intratumor heterogeneity characterize the immunohistochemical expression of epithelial-mesenchymal transition markers in high-grade clear cell renal cell carcinomas. Multisite tumor sampling protocol outperforms routine sampling in detecting immunohistochemical intratumor heterogeneity.

Intratumoural heterogeneity may hinder precision medicine strategies in patients with clear cell renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC) is an heterogeneous tumour at architectural, cellular and molecular level, a reason why the 2014 International Society of Urological Pathology consensus recommended wide sampling of RCC masses to include at least 1 block/cm of tumour together with perpendicular sections of the tumour/perinephric fat interface and the tumour/renal sinus interface. Intratumoural molecular heterogeneity may be a limitation at the moment of defining precision medicine strategies based on gene mutation status. This study analyses the presence of any mutation of KRAS, NRAS, BRAF, PIK3CA, ALK, ERBB2, DDR2, MAP2K1, RET and EGFR genes in 20 tissue blocks from a case of ccRCC and its metastasis. We observed the presence of the mutation at pH1047R of PIK3CA gene in five samples of the tumour, while the remaining 15 samples did not show any mutation at PIK3CA or any other investigated gene. There is a great need to develop novel RCC sampling strategies to overcome tumour heterogeneity prior to define precision oncology strategies.

Tumour necrosis factor receptor-associated factor-1 (TRAF-1) expression is increased in renal cell carcinoma patient serum but decreased in cancer tissue compared with normal: potential biomarker significance

Renal cell carcinoma (RCC) generally has a poor prognosis because of late diagnosis and metastasis. We have previously described decreased tumour necrosis factor receptor-associated factor-1 (TRAF-1) in RCC compared with paired normal kidney in a patient cohort in Australia. In the present study, TRAF-1 expression in clear cell RCC (ccRCC) and normal kidney was again compared, but in a cohort from University Malaya Medical Centre. Serum TRAF-1 was also evaluated in RCC and normal samples.Immunohistochemistry with automated batch staining and Aperio ImageScope morphometry was used to compare TRAF-1 in 61 ccRCC with paired normal kidney tissue. Serum from 15 newly diagnosed and untreated ccRCC and 15 healthy people was tested for TRAF-1 using ELISA.In this cohort, TRAF-1 was highly expressed in proximal tubular epithelium of normal kidney, and significantly decreased in ccRCC tissue (p < 0.001). Conversely, TRAF-1 in serum from ccRCC patients was significantly increased over control serum (132 ± 30 versus 54 ± 14 pg/mL, respectively; p = 0.013).Decreased TRAF-1 in RCC tissue, reported previously, was confirmed. This, along with significantly increased serum TRAF-1 may indicate the protein is actively secreted during development and progression of ccRCC. Therefore, the increased serum TRAF-1 may be a useful non-invasive indicator of RCC development.

A divide-and-conquer strategy in tumor sampling enhances detection of intratumor heterogeneity in routine pathology: A modeling approach in clear cell renal cell carcinoma

Intratumor heterogeneity (ITH) is an inherent process in cancer development which follows for most of the cases a branched pattern of evolution, with different cell clones evolving independently in space and time across different areas of the same tumor. The determination of ITH (in both spatial and temporal domains) is nowadays critical to enhance patient treatment and prognosis. Clear cell renal cell carcinoma (CCRCC) provides a good example of ITH. Sometimes the tumor is too big to be totally analyzed for ITH detection and pathologists decide which parts must be sampled for the analysis. For such a purpose, pathologists follow internationally accepted protocols. In light of the latest findings, however, current sampling protocols seem to be insufficient for detecting ITH with significant reliability. The arrival of new targeted therapies, some of them providing promising alternatives to improve patient survival, pushes the pathologist to obtain a truly representative sampling of tumor diversity in routine practice. How large this sampling must be and how this must be performed are unanswered questions so far.  Here we present a very simple method for tumor sampling that enhances ITH detection without increasing costs. This method follows a divide-and-conquer (DAC) strategy, that is, rather than sampling a small number of large-size tumor-pieces as the routine protocol (RP) advises, we suggest sampling many small-size pieces along the tumor. We performed a computational modeling approach to show that the usefulness of the DAC strategy is twofold: first, we show that DAC outperforms RP with similar laboratory costs, and second, DAC is capable of performing similar to total tumor sampling (TTS) but, very remarkably, at a much lower cost. We thus provide new light to push forward a shift in the paradigm about how pathologists should sample tumors for achieving efficient ITH detection.

A divide-and-conquer strategy in tumor sampling enhances detection of intratumor heterogeneity in routine pathology: A modeling approach in clear cell renal cell carcinoma

Intratumor heterogeneity (ITH) is an inherent process in cancer development which follows for most of the cases a branched pattern of evolution, with different cell clones evolving independently in space and time across different areas of the same tumor. The determination of ITH (in both spatial and temporal domains) is nowadays critical to enhance patient treatment and prognosis. Clear cell renal cell carcinoma (CCRCC) provides a good example of ITH. Sometimes the tumor is too big to be totally analyzed for ITH detection and pathologists decide which parts must be sampled for the analysis. For such a purpose, pathologists follow internationally accepted protocols. In light of the latest findings, however, current sampling protocols seem to be insufficient for detecting ITH with significant reliability. The arrival of new targeted therapies, some of them providing promising alternatives to improve patient survival, pushes the pathologist to obtain a truly representative sampling of tumor diversity in routine practice. How large this sampling must be and how this must be performed are unanswered questions so far.  Here we present a very simple method for tumor sampling that enhances ITH detection without increasing costs. This method follows a divide-and-conquer (DAC) strategy, that is, rather than sampling a small number of large-size tumor-pieces as the routine protocol (RP) advises, we suggest sampling many small-size pieces along the tumor. We performed a computational modeling approach to show that the usefulness of the DAC strategy is twofold: first, we show that DAC outperforms RP with similar laboratory costs, and second, DAC is capable of performing similar to total tumor sampling (TTS) but, very remarkably, at a much lower cost. We thus provide new light to push forward a shift in the paradigm about how pathologists should sample tumors for achieving efficient ITH detection.

Snail heterogeneity in clear cell renal cell carcinoma

Background

Intratumor heterogeneity may be responsible of the unpredictable aggressive clinical behavior that some clear cell renal cell carcinomas display. This clinical uncertainty may be caused by insufficient sampling, leaving out of histological analysis foci of high grade tumor areas. Although molecular approaches are providing important information on renal intratumor heterogeneity, a focus on this topic from the practicing pathologist’ perspective is still pending.

Methods

Four distant tumor areas of 40 organ-confined clear cell renal cell carcinomas were selected for histopathological and immunohistochemical evaluation. Tumor size, cell type (clear/granular), Fuhrman’s grade, Staging, as well as immunostaining with Snail, ZEB1, Twist, Vimentin, E-cadherin, β-catenin, PTEN, p-Akt, p110α, and SETD2, were analyzed for intratumor heterogeneity using a classification and regression tree algorithm.

Results

Cell type and Fuhrman’s grade were heterogeneous in 12.5 and 60 % of the tumors, respectively. If cell type was homogeneous (clear cell) then the tumors were low-grade in 88.57 % of cases. Immunostaining heterogeneity was significant in the series and oscillated between 15 % for p110α and 80 % for Snail. When Snail immunostaining was homogeneous the tumor was histologically homogeneous in 100 % of cases. If Snail was heterogeneous, the tumor was heterogeneous in 75 % of the cases. Average tumor diameter was 4.3 cm. Tumors larger than 3.7 cm were heterogeneous for Vimentin immunostaining in 72.5 % of cases. Tumors displaying negative immunostaining for both ZEB1 and Twist were low grade in 100 % of the cases.

Conclusions

Intratumor heterogeneity is a common event in clear cell renal cell carcinoma, which can be monitored by immunohistochemistry in routine practice. Snail seems to be particularly useful in the identification of intratumor heterogeneity. The suitability of current sampling protocols in renal cancer is discussed.

Intratumor heterogeneity in clear cell renal cell carcinoma: a review for the practicing pathologist

Intertumor heterogeneity, defined as the spectrum of morphological differences found in similar tumors in different patients, is a well-known event for pathologists. However, recent molecular studies have pointed to intratumor heterogeneity as one of the most important issues in human neoplasia in the next years. Clear cell renal cell carcinoma is an example of an intrinsically heterogeneous neoplasm, and some of the most salient advances in the knowledge of intratumor heterogeneity have been developed on it. This review intends to analyze this phenomenon in this tumor from the practicing pathologist's point of view. A careful study of the surgical specimen and an exhaustive tumor sampling are mandatory to keep relevant information. Currently accepted protocols designed for renal tumor sampling may be insufficient. As a result, a different approach to tumor sampling is advisable to ascertain that intratumor heterogeneity, if present, will be well represented in the selected material.

How should clinicians address intratumour heterogeneity in clear cell renal cell carcinoma?

PURPOSE OF REVIEW

Despite the availability of multiple targeted therapies, the 5-year survival rate of patients with metastatic clear cell renal cell carcinoma (ccRCC) rarely exceeds 10%. Recent insights into the mutational landscape and evolutionary dynamics of ccRCC have offered up a plausible explanation for these outcomes. The purpose of this review is to link the research findings to potential changes in clinical practice.

RECENT FINDINGS

Intratumour heterogeneity (ITH) dominates the evolutionary landscape in ccRCC at the genetic, transcriptomic and proteomic level. Spatial and temporal separation of tumour subclones within the primary tumour as well as between primary and metastatic sites has been demonstrated at single nucleotide resolution. In the cases analysed to date, approximately two-thirds of somatic mutations are not shared between multiple biopsies from the same primary tumour. Very few of the key disease-driving events are shared across all primary tumour regions (with the exception of VHL and loss of chromosome 3p), whereas the majority are restricted to one or more tumour regions (TP53, SETD2, BAP1, PTEN, mTOR, PIK3CA and KDM5C).

SUMMARY

ITH must be considered in the management of ccRCC with respect to diagnostic procedures, prognostic and predictive biomarkers and drug development.