A gene signature to determine metastatic behavior in thymomas

Non-Mutational Key Features in the Biology of Thymomas

Thymomas (THs) are a unique group of heterogeneous tumors of the thymic epithelium. In particular, the subtypes B2 and B3 tend to be aggressive and metastatic. Radical tumor resection remains the only curative option for localized tumors, while more advanced THs require multimodal treatment. Deep sequencing analyses have failed to identify known oncogenic driver mutations in TH, with the notable exception of the GTF2I mutation, which occurs predominantly in type A and AB THs. However, there are multiple alternative non-mutational mechanisms (e.g., perturbed thymic developmental programs, metabolism, non-coding RNA networks) that control cellular behavior and tumorigenesis through the deregulation of critical molecular pathways. Here, we attempted to show how the results of studies investigating such alternative mechanisms could be integrated into a current model of TH biology. This model could be used to focus ongoing research and therapeutic strategies.

The Molecular Landscape of Thymic Epithelial Tumors: A Comprehensive Review

Thymic epithelial tumors (TETs) are characterized by their extreme rarity and variable clinical presentation, with the inadequacy of the use of histological classification alone to distinguish biologically indolent from aggressive cases. The utilization of Next Generation Sequencing (NGS) to unravel the intricate genetic landscape of TETs could offer us a comprehensive understanding that is crucial for precise diagnoses, prognoses, and potential therapeutic strategies. Despite the low tumor mutational burden of TETS, NGS allows for exploration of specific genetic signatures contributing to TET onset and progression. Thymomas exhibit a limited mutational load, with prevalent GTF2I and HRAS mutations. On the other hand, thymic carcinomas (TCs) exhibit an elevated mutational burden, marked by frequent mutations in TP53 and genes associated with epigenetic regulation. Moreover, signaling pathway analyses highlight dysregulation in crucial cellular functions and pathways. Targeted therapies, and ongoing clinical trials show promising results, addressing challenges rooted in the scarcity of actionable mutations and limited genomic understanding. International collaborations and data-sharing initiatives are crucial for breakthroughs in TETs research.

Genetic insights into thymic carcinomas and thymic neuroendocrine neoplasms denote prognosis signatures and pathways

BACKGROUND

Thymic carcinomas (TCs) and thymic neuroendocrine neoplasms (TNENs) are two aggressive subtypes of thymic malignancy. Traditional therapy for advanced TCs and TNENs has limited outcome. New genomic profiling of TCs and TNENs might provide insights that contribute to the development of new treatment approaches.

METHODS

We used gene panel sequencing technologies to investigate the genetic aberrations of 32 TC patients and 15 TNEN patients who underwent surgery at Shanghai Chest Hospital between 2015 and 2017. Patient samples were sequenced using a 324-gene platform with licensed technologies. In this study, we focused on clinically relevant genomic alterations (CRGAs), which are previously proven to be pathogenic alterations, to identify the pathology-specific mutational patterns, prognostic signatures of TCs and TNENs.

RESULTS

The mutational profiles between TCs and TNENs were diverse. The genetic alterations that ranked highest in TCs were in CDKN2A, TP53, ASXL1, CDKN2B, PIK3C2G, PTCH1, and ROS1 , while those in TNENs were in MEN1, MLL2, APC, RB1 , and TSC2 . Prognostic analysis showed that mutations of ROS1, CDKN2A, CDKN2B, BRAF, and BAP1 were significantly associated with worse outcomes in TC patients, and that mutation of ERBB2 indicated shortened disease-free survival (DFS) and overall survival (OS) in TNEN patients. Further investigation found that the prognosis-related genes were focused on signal pathways of cell cycle control, chromatin remodeling/DNA methylation, phosphoinositide 3-kinases (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR), and receptor tyrosine kinase (RTK)/RAS/mitogen-activated protein kinase (MAPK) signaling.

CONCLUSION

We profiled the mutational features of 47 Chinese patients with thymic malignancy of diverse pathologic phenotypes to uncover the integrated genomic landscape of these rare tumors, and identified the pathology-specific mutational patterns, prognostic signatures, and potential therapeutic targets for TCs and TNENs.

Prognosis of Concurrent Versus Sequential Chemo-Radiotherapy Induction Followed by Surgical Resection in Patients with Advanced Thymic Epithelial Tumors: A Retrospective Study

BACKGROUND

This study aimed to evaluate the prognosis of concurrent chemo-radiotherapy (CCRT) versus sequential chemo-radiotherapy (SCRT) induction followed by surgical resection in patients with advanced thymic epithelial tumors (TETs).

METHODS

This retrospective study included patients with advanced TETs who underwent CCRT or SCRT induction followed by surgical resection at the Second General Hospital of Guangdong Province between January 2008 and December 2019. The primary outcomes were induction response rate and surgical complete resection rate. The secondary outcomes were surgery combined resection, post-induction T staging, postoperative TNM staging, postoperative pathological tumor regression grade, progression-free survival (PFS) and overall survival (OS), and adverse events (AEs).

RESULTS

A total of 31 patients were included, 15 of whom received CCRT and the other 16 SCRT. The induction response rates were 80.0 and 62.5%, respectively, the post-induction step-down rates were 46.7 and 31.3%, respectively, and the post-induction R0 resection rates were 80.0 and 68.8%, respectively, without significant differences between CCRT and SCRT groups (all P > 0.05). The 5-year OS rate was 64.2 and 51.6%, respectively, and PFS was 42.3 and 21.4%, respectively, without significant differences between CCRT and SCRT groups (both P > 0.05). AEs in the hematologic system were significantly higher with CCRT compared with SCRT (P = 0.009).

CONCLUSIONS

Patients with advanced TETs might have a good prognosis with both CCRT and SCRT induction therapy, while SCRT induction may result in a lower probability of AEs in the hematologic system.

Genomic clustering analysis identifies molecular subtypes of thymic epithelial tumors independent of World Health Organization histologic type

Further characterization of thymic epithelial tumors (TETs) is needed. Genomic information from 102 evaluable TETs from The Cancer Genome Atlas (TCGA) dataset and from the IU-TAB-1 cell line (type AB thymoma) underwent clustering analysis to identify molecular subtypes of TETs. Six novel molecular subtypes (TH1-TH6) of TETs from the TCGA were identified, and there was no association with WHO histologic subtype. The IU-TAB-1 cell line clustered into the TH4 molecular subtype and in vitro testing of candidate therapeutics was performed. The IU-TAB-1 cell line was noted to be resistant to everolimus (mTORC1 inhibitor) and sensitive to nelfinavir (AKT1 inhibitor) across the endpoints measured. Sensitivity to nelfinavir was due to the IU-TAB-1 cell line’s gain-of function (GOF) mutation in PIK3CA and amplification of genes observed from array comparative genomic hybridization (aCGH), including AURKA, ERBB2, KIT, PDGFRA and PDGFB, that are known upregulate AKT, while resistance to everolimus was primarily driven by upregulation of downstream signaling of KIT, PDGFRA and PDGFB in the presence of mTORC1 inhibition. We present a novel molecular classification of TETs independent of WHO histologic subtype, which may be used for preclinical validation studies of potential candidate therapeutics of interest for this rare disease.

Mutation profile and immunoscore signature in thymic carcinomas: An exploratory study and review of the literature

Background

Significant efforts have been made to investigate the molecular pathways involved in thymic carcinogenesis. However, genetic findings have still not impacted clinical practice. The aim of this exploratory trial was to evaluate the immunoscore and molecular profile of a series of thymic carcinomas (TCs), correlating this data with clinical outcome.

Methods

Formalin‐fixed, paraffin‐embedded (FFPE) TC tissues were retrieved from our center archive. The immunoscore was evaluated according to Angell and Gallon. DNA was extracted from FFPE tumor samples and, when available, from adjacent histologically normal tissues. Next‐generation sequencing (NGS) was performed targeting hotspot regions of 50 oncogenes and tumor suppressor genes.

Results

A series of 15 TCs were analyzed. After a median follow‐up of 82.4 months, the median overall survival was 104.7 months. The immunoscore was >2 in 5/15 patients (33%). Among the investigated genes, absence of mutations was observed in 5/15 patients (33%), whereas three variants in 1/15 (6%) patient, two variants in 4/15 (26%) patients, and one variant in 5/15 patients (33%) were found. The most recurrently mutated genes were FGFR3 (five mutations) and CDKN2A (three mutations, two of which were nonsense). Patients with CDKN2A loss showed a statistically significantly worse survival (P = 0.0013), whereas patients with FGFR3 mutations showed a statistically significantly better survival (P = 0.048).

Conclusions

This study adds data to the few existing reports on the mutational landscape of TCs, providing the first comprehensive analysis to date. Here, we confirm the low rate of mutations in TCs and suggest FGFR3 and CDKN2A mutations as intriguing potential therapeutic targets.

Correlation of genomic alterations and PD-L1 expression in thymoma

Thymic epithelial tumors (TETs) include several anterior mediastinal malignant tumours: thymomas, thymic carcinomas and thymic neuroendocrine cancers. There is significant variety in the biologic features and clinical course of TETs and many attempts have been made to identify target genes for successful therapy of TETs. Next generation sequencing (NGS) represents a huge advancement in diagnostics and these new molecular technologies revealed that thymic neoplasms have the lowest tumor mutation burden among all adult malignant tumours with a different pattern of molecular aberrations in thymomas and thymic carcinomas. As for the PD-L1 expression in tumor cells in thymoma and thymic carcinoma, it varies a lot in published studies, with findings of PD-L1 expression from 23% to 92% in thymoma and 36% to 100% in thymic carcinoma. When correlated PD-L1 expression with disease stage some controversial results were obtained, with no association with tumor stage in most studies. This is, at least in part, explained by the fact that several diverse PD-L1 immunohistochemical tests were used in each trial, with four different antibodies (SP142, SP263, 22C3, and 28-8), different definition of PD-L1 positivity and cutoff values throughout the studies as well. There is a huge interest in using genomic features to produce predictive genomic-based immunotherapy biomarkers, particularly since recent data suggest that certain tumor-specific genomic alterations, either individually or in combination, appear to influence immune checkpoint activity and better responses as the outcome, so as such in some cancer types they may complement existing biomarkers to improve the selection criteria for immunotherapy.

Immunobiology of Thymic Epithelial Tumors: Implications for Immunotherapy with Immune Checkpoint Inhibitors

Thymic epithelial tumors (TETs) are a group of rare thoracic malignancies, including thymic carcinomas (TC) and thymomas (Tm). Autoimmune paraneoplastic diseases are often observed in TETs, especially Tms. To date, chemotherapy is still the standard treatment for advanced disease. Unfortunately, few therapeutic options are available for relapsed/refractory TETs. In the last few years, the deepening of knowledge on thymus' immunobiology and involved altered genetic pathways have laid the foundation for new treatment options in these rare neoplasms. Recently, the immunotherapy revolution has landed in TETs, showing both a dark and light side. Indeed, despite the survival benefit, the occurrence of severe autoimmune treatment-related adverse events has risen crescent uncertainty about the feasibility of immunotherapy in these patients, prone to autoimmunity for their cancer biology. In this review, after summarizing immunobiology and immunopathology of TETs, we discuss available data on immune-checkpoint inhibitors and future perspectives of this therapeutic strategy.

lncRNAs classifier to accurately predict the recurrence of thymic epithelial tumors

Background

Long non‐coding RNAs (lncRNAs), which have little or no ability to encode proteins, have attracted special attention due to their potential role in cancer disease. In this study we aimed to establish a lncRNAs classifier to improve the accuracy of recurrence prediction for thymic epithelial tumors (TETs).

Methods

TETs RNA sequencing (RNA‐seq) data set and the matched clinicopathologic information were downloaded from the Cancer Genome Atlas. Using univariate Cox regression and least absolute shrinkage and selection operator (LASSO) analysis, we developed a lncRNAs classifier related to recurrence. Functional analysis was conducted to investigate the potential biological processes of the lncRNAs target genes. The independent prognostic factors were identified by Cox regression model. Additionally, predictive ability and clinical application of the lncRNAs classifier were assessed, and compared with the Masaoka staging by receiver operating characteristic (ROC) analysis and decision curve analysis (DCA).

Results

Four recurrence‐free survival (RFS)‐related lncRNAs were identified, and the classifier consisting of the identified four lncRNAs was able to effectively divide the patients into high and low risk subgroups, with an area under curve (AUC) of 0.796 (three‐year RFS) and 0.788 (five‐year RFS), respectively. Multivariate analysis indicated that the lncRNAs classifier was an independent recurrence risk factor. The AUC of the lncRNAs classifier in predicting RFS was significantly higher than the Masaoka staging system. Decision curve analysis further demonstrated that the lncRNAs classifier had a larger net benefit than the Masaoka staging system.

Conclusions

A lncRNAs classifier for patients with TETs was an independent risk factor for RFS despite other clinicopathologic variables. It generated more accurate estimations of the recurrence probability when compared to the Masaoka staging system, but additional data is required before it can be used in clinical practice.

Elevated CRP levels predict poor outcome and tumor recurrence in patients with thymic epithelial tumors: A pro- and retrospective analysis

Objective

Scarce information exists on the pathogenesis of thymic epithelial tumors (TETs), comprising thymomas, thymic carcinomas (TCs) and neuroendocrine tumors. C-reactive protein (CRP) increases during certain malignancies. We aimed to investigate the clinical relevance of CRP in patients with TETs.

Results

Pretreatment CRP serum concentrations were significantly elevated in patients with TETs, particularly TCs and metastatic TETs. After complete tumor resection CRP serum concentrations were decreased (p = 0.135) but increased significantly in case of tumor recurrence (p = 0.001). High pretreatment CRP was associated with significantly worse 5- and 10-year freedom-from recurrence (FFR) (p = 0.010) and was a negative prognostic factor for FFR (HR 3.30; p = 0.015). IL-6 (not IL-1β) serum concentrations were significantly elevated in patients with TETs but we did not detect CRP tissue expression in TETs.

Materials and Methods

Pretreatment CRP serum concentrations were retrospectively analyzed from 128 surgical patients (1990–2015). In a subset of 68 patients longitudinal analysis of CRP was performed. Additionally, immunohistochemical tumor CRP expression and serum concentrations of interleukin (IL)-6 and IL-1β were measured.

Conclusions

Hence, diagnostic measurement of serum CRP might be useful to indicate highly aggressive TETs and to make doctors consider tumor recurrences during oncological follow-up.

The Integrated Genomic Landscape of Thymic Epithelial Tumors

Thymic epithelial tumors (TETs) are one of the rarest adult malignancies. Among TETs, thymoma is the most predominant, characterized by a unique association with autoimmune diseases, followed by thymic carcinoma, which is less common but more clinically aggressive. Using multi-platform omics analyses on 117 TETs, we define four subtypes of these tumors defined by genomic hallmarks and an association with survival and World Health Organization histological subtype. We further demonstrate a marked prevalence of a thymoma-specific mutated oncogene, GTF2I, and explore its biological effects on multi-platform analysis. We further observe enrichment of mutations in HRAS, NRAS, and TP53. Last, we identify a molecular link between thymoma and the autoimmune disease myasthenia gravis, characterized by tumoral overexpression of muscle autoantigens, and increased aneuploidy.

Thymic Epithelial Tumors phenotype relies on miR-145-5p epigenetic regulation

BACKGROUND

Thymoma and thymic carcinoma are the most frequent subtypes of thymic epithelial tumors (TETs). A relevant advance in TET management could derive from a deeper molecular characterization of these neoplasms. We previously identified a set of microRNA (miRNAs) differentially expressed in TETs and normal thymic tissues and among the most significantly deregulated we described the down-regulation of miR-145-5p in TET. Here we describe the mRNAs diversely regulated in TETs and analyze the correlation between these and the miRNAs previously identified, focusing in particular on miR-145-5p. Then, we examine the functional role of miR-145-5p in TETs and its epigenetic transcriptional regulation.

METHODS

mRNAs expression profiling of a cohort of fresh frozen TETs and normal tissues was performed by microarray analysis. MiR-145-5p role in TETs was evaluated in vitro, modulating its expression in a Thymic Carcinoma (TC1889) cell line. Epigenetic transcriptional regulation of miR-145-5p was examined by treating the TC1889 cell line with the HDAC inhibitor Valproic Acid (VPA).

RESULTS

Starting from the identification of a 69-gene signature of miR-145-5p putative target mRNAs, whose expression was inversely correlated to that of miR-145-5p, we followed the expression of some of them in vitro upon overexpression of miR-145-5p; we observed that this resulted in the down-regulation of the target genes, impacting on TETs cancerous phenotype. We also found that VPA treatment of TC1889 cells led to miR-145-5p up-regulation and concomitant down-regulation of miR-145-5p target genes and exhibited antitumor effects, as indicated by the induction of cell cycle arrest and by the reduction of cell viability, colony forming ability and migration capability. The importance of miR-145-5p up-regulation mediated by VPA is evidenced by the fact that hampering miR-145-5p activity by a LNA inhibitor reduced the impact of VPA treatment on cell viability and colony forming ability of TET cells. Finally, we observed that VPA was also able to enhance the response of TET cells to cisplatin and erlotinib.

CONCLUSIONS

Altogether our results suggest that the epigenetic regulation of miR-145-5p expression, as well as the modulation of its functional targets, could be relevant players in tumor progression and treatment response in TETs.

Anterior mediastinum invasion by multiple myeloma: A case report

Multiple myeloma (MM) is a clonal proliferation of malignant plasma cells in the bone marrow (BM) that secretes monoclonal paraproteins in the blood serum and urine. Bone marrow MM cells can invade and damage the functions of other tissues and organs, such as the lungs, spleen, liver, pancreas, kidneys and lymph nodes. However, the invasion of MM cells primarily located in the BM to the anterior mediastinum at the site of the thymus is an extremely rare event. The current study reports the case of a 53-year-old female who presented with MM with involvement of the anterior mediastinum. The diagnosis was based on clinical imaging analyses and the results from BM and laboratory examinations, local biopsy pathology and immunohistochemistry. The patient was administered two courses of chemotherapy (epirubicin, dexamethasone and thalidomide). As a result, the tumor reduced in size, but the laboratory examination indicated no significant change. Next, the patient was switched to one course of PAD chemotherapy (bortezomib, epirubicin and dexamethasone). The original tumor was significantly reduced in size following this chemotherapy, and all the indicators improved. The present study suggests that invasion of the thymus by MM may lead to immune disturbance arising from the abnormal thymus gland. In the clinic, extramedullary plasmacytoma in the thymus should be carefully distinguished from thymoma.

Metastatic type A thymoma: morphological and genetic correlation

AIMS

The vast majority of type A thymomas are diagnosed in tumour stages 1 or 2, and metastatic cases are exceedingly rare. The histological and genetic features of such metastatic type A thymomas have not been described in detail.

METHODS AND RESULTS

Five metastatic type A thymomas in tumour stage Masaoka IVb that had been reviewed by a panel of expert pathologists were analysed using comparative genomic hybridization (CGH). Cases 1, 2 and 3 showed the prototypical morphology of type A thymomas with mainly solid growth patterns. These cases displayed only very subtle nuclear irregularities and slight nuclear crowding, but no other atypical features. Mitoses were absent. Cases 3 and 4, in contrast, had a distinctly atypical morphology. CGH revealed partially recurrent alterations in four cases (with and without atypical morphology), including gains on chromosome 1q (one case), 17q (two cases), chromosome 19 (three cases) and 22q (one case) and losses on chromosome 17p (two cases) and 22q (one case).

CONCLUSION

Rare metastatic type A thymomas, both with typical and 'atypical' histological features, show partially recurrent genomic alterations that differ from the much more frequent localized and indolent tumours. The fact that these alterations were recurring points to a link between clinical behaviour and molecular features. Our findings may have implications for the management and treatment of such tumours.

The digital age of melanoma management: detection and diagnostics

New technologies are increasingly impacting the way melanoma is detected and diagnosed. Devices, software and diagnostics abound, ranging from smartphone applications that purport to predict which lesions are likely to be malignant, to genomic analysis of low-stage melanomas to predict metastatic risk. The purpose of this review is to concisely update practitioners on the research behind the latest tools available for melanoma detection and diagnosis, as well as the implications of these technologies for melanoma management.

State of the art of genetic alterations in thymic epithelial tumors

The rapid advent of technology in recent years has resulted in a substantial increase in our knowledge of the molecular underpinnings of thymic epithelial tumors. In addition to previously described chromosomal aberrations and alterations in DNA methylation, genome sequencing has helped unravel hitherto unknown mutations in these tumors. Attempts are also being made to develop gene signatures to help in the identification of patients likely to benefit from adjuvant therapy. Some of the recently identified genetic alterations have the potential to serve as targets for biological therapy, thus opening newer avenues for treatment of thymic epithelial tumors and increasing the number of effective options for treatment of recurrent or refractory disease.

Gene expression profiling for molecular staging of cutaneous melanoma in patients undergoing sentinel lymph node biopsy

BACKGROUND

A gene expression profile (GEP) test able to accurately identify risk of metastasis for patients with cutaneous melanoma has been clinically validated.

OBJECTIVE

We aimed for assessment of the prognostic accuracy of GEP and sentinel lymph node biopsy (SLNB) tests, independently and in combination, in a multicenter cohort of 217 patients.

METHODS

Reverse transcription polymerase chain reaction (RT-PCR) was performed to assess the expression of 31 genes from primary melanoma tumors, and SLNB outcome was determined from clinical data. Prognostic accuracy of each test was determined using Kaplan-Meier and Cox regression analysis of disease-free, distant metastasis-free, and overall survivals.

RESULTS

GEP outcome was a more significant and better predictor of each end point in univariate and multivariate regression analysis, compared with SLNB (P < .0001 for all). In combination with SLNB, GEP improved prognostication. For patients with a GEP high-risk outcome and a negative SLNB result, Kaplan-Meier 5-year disease-free, distant metastasis-free, and overall survivals were 35%, 49%, and 54%, respectively.

LIMITATIONS

Within the SLNB-negative cohort of patients, overall risk of metastatic events was higher (∼30%) than commonly found in the general population of patients with melanoma.

CONCLUSIONS

In this study cohort, GEP was an objective tool that accurately predicted metastatic risk in SLNB-eligible patients.

Development of a prognostic genetic signature to predict the metastatic risk associated with cutaneous melanoma

PURPOSE

The development of a genetic signature for the identification of high-risk cutaneous melanoma tumors would provide a valuable prognostic tool with value for stage I and II patients who represent a remarkably heterogeneous group with a 3% to 55% chance of disease progression and death 5 years from diagnosis.

EXPERIMENTAL DESIGN

A prognostic 28-gene signature was identified by analysis of microarray expression data. Primary cutaneous melanoma tumor tissue was evaluated by RT-PCR for expression of the signature, and radial basis machine (RBM) modeling was performed to predict risk of metastasis.

RESULTS

RBM analysis of cutaneous melanoma tumor gene expression reports low risk (class 1) or high risk (class 2) of metastasis. Metastatic risk was predicted with high accuracy in development (ROC = 0.93) and validation (ROC = 0.91) cohorts of primary cutaneous melanoma tumor tissue. Kaplan-Meier analysis indicated that the 5-year disease-free survival (DFS) rates in the development set were 100% and 38% for predicted classes 1 and 2 cases, respectively (P < 0.0001). DFS rates for the validation set were 97% and 31% for predicted classes 1 and 2 cases, respectively (P < 0.0001). Gene expression profile (GEP), American Joint Committee on Cancer stage, Breslow thickness, ulceration, and age were independent predictors of metastatic risk according to Cox regression analysis.

CONCLUSIONS

The GEP signature accurately predicts metastasis risk in a multicenter cohort of primary cutaneous melanoma tumors. Preliminary Cox regression analysis indicates that the signature is an independent predictor of metastasis risk in the cohort presented.

Identification of a suitable qPCR reference gene in metastatic clear cell renal cell carcinoma

There is no data on reference gene (RG) selection in metastatic clear-cell renal cell carcinoma (mccRCC) for quantitative PCR (qPCR) data normalization. We aimed at selecting the most stable RG for further determination of new prognostic markers. Thirty-five nonmetastatic and 35 mccRCC patients undergoing radical nephrectomy were included. Paired primary tumor (T, n = 70) and normal (C, n = 70) kidney fragments were collected; from 12 out of 35 mccRCC cases, we also collected metastasized regional lymph nodes and adrenal gland tissues (M, n = 12). After RNA extraction, reverse transcription and qPCR were performed. Samples were divided into four analyzed groups. Fifteen candidate RGs were tested by RefFinder tool and manual statistics. To present the importance of RG selection, TP53 gene expression levels in samples were normalized with the use of RG data. RPL13 gene was the most stable RG in analysis of 35 primary tumor nonmetastatic versus 35 mccRCC samples and matched metastasized T/C/M samples (n = 12, each group). GUSB was the most suitable RG in total 152 samples and in paired T and C (n = 140) kidney samples. Expression of GUSB, RPL13, and the RPL13 + RPLP0 pair were independent of clinical/sample variables. Normalization of TP53 expression levels showed variability of GAPDH and ACTB assays. GUSB or RPL13 assays should be used in mccRCC for qPCR data normalization whereas GAPDH and ACTB assays should be avoided. Prior RG studies should precede each qPCR gene expression study since RG selection is associated with the origin and proportion of specimens.