Haploinsufficiency in tumor predisposition syndromes: altered genomic transcription in morphologically normal cells heterozygous for VHL or TSC mutation.

Robert G Uzzo,Levy Kopelovich,Alfonso Bellacosa,Karthik Devarajan,Christopher J Ricketts,Eleonora Sementino,Peggy Conrad,Margie L Clapper,Lisa Vanderveer ,Andrew K Godwin,Kerry S Campbell,Cathy D Vocke,Mitchell Cheung,W Marston Linehan,Rossella Tricarico,Sharon Howard,Elizabeth P Henske,Anthony T Yeung,Alfred G Knudson,Eric A Ross,Elena Caretti,Suraj Peri,Craig W Menges,James A Crowell,Émmanuelle Nicolas ,Joseph R Testa

doi:10.18632/oncotarget.12192

Abstract

Tumor suppressor genes and their effector pathways have been identified for many dominantly heritable cancers, enabling efforts to intervene early in the course of disease. Our approach on the subject of early intervention was to investigate gene expression patterns of morphologically normal one-hit cells before they become hemizygous or homozygous for the inherited mutant gene which is usually required for tumor formation. Here, we studied histologically non-transformed renal epithelial cells from patients with inherited disorders that predispose to renal tumors, including von Hippel-Lindau (VHL) disease and Tuberous Sclerosis (TSC). As controls, we studied histologically normal cells from non-cancerous renal epithelium of patients with sporadic clear cell renal cell carcinoma (ccRCC). Gene expression analyses of VHLmut/wt or TSC1/2mut/wt versus wild-type (WT) cells revealed transcriptomic alterations previously implicated in the transition to precancerous renal lesions. For example, the gene expression changes in VHLmut/wt cells were consistent with activation of the hypoxia response, associated, in part, with the Warburg effect. Knockdown of any remaining VHL mRNA using shRNA induced secondary expression changes, such as activation of NF?B and interferon pathways, that are fundamentally important in the development of RCC. We posit that this is a general pattern of hereditary cancer predisposition, wherein haploinsufficiency for VHL or TSC1/2, or potentially other tumor susceptibility genes, is sufficient to promote development of early lesions, while cancer results from inactivation of the remaining normal allele. The gene expression changes identified here are related to the metabolic basis of renal cancer and may constitute suitable targets for early intervention.

Highlights

The discovery of tumor suppressor genes (TSGs) and their pivotal role in the etiology of hereditary cancer presents the opportunity to study phenotypically normalappearing, histologically non-transformed target tissues, for possible intervention [1]
Our primary goal was to compare transcriptomes of MNNT renal epithelial cells harboring a mutation in one allele of von Hippel-Lindau disease (VHL) or TSC1/2, to monitor the earliest gene expression changes associated with one-hit inactivation of a given TSG [11, 16, 25]
MNNT one-hit cells were obtained from six patients diagnosed with TSC1 or TSC2 based on distinctive clinical features, mutational analysis is not available for this TSC1/2 patient group

Summary

Introduction

The discovery of tumor suppressor genes (TSGs) and their pivotal role in the etiology of hereditary cancer presents the opportunity to study phenotypically normalappearing, histologically non-transformed target tissues, for possible intervention [1]. This approach may lead to early intervention of clinically-identifiable preneoplastic lesions such as polyposis of the colon and squamous or basal skin cancers, wherein hundreds of lesions appear before progression to carcinoma [2]. We report aberrant patterns of gene expression in non-transformed VHL- or TSC1/2”one-hit” renal epithelial cells from patients with germline VHL or TSC1/2 mutations. Transcriptional alterations have been described in one-hit cells from target tissues of patients with dominantly inherited susceptibility to colon or breast cancers [9,10,11]

Methods

Results

Conclusion