Identification of new targets for the POD1 / TCF21 transcription factor in human tumor cell cultures.

Author(s)

Barbara dos Santos Passaia

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Ciências Biomédicas (ICB/SDI)
• Defense date: 2020-11-10

Examining board members

Claudimara Ferini Pacicco Lotfi; Vanessa Morais Freitas; Emilia Modolo Pinto; Ericka Barbosa Trarbach

• Advisor: Claudimara Ferini Pacicco Lotfi

Abstract

Steroidogenic factor 1 (SF1/NR5A1) and homologous liver receptor (LRH1/ NR5A2) are important transcription factors in the regulation of steroidogenesis, adrenals and gonads, respectively. SF1/NR5A1 and LRH1/NR5A2 can be regulated by some factors, among them is the bHLH type transcription factor, TCF21. TCF21 is able to inhibit the endogenous expression of SF1/NR5A1 and steroidogenic enzymes by binding to the E-box site of the SF1/NR5A1 promoter from human adrenocortical carcinoma cell cultures and normal rat adrenal cultures. However, in hepatocarcinoma cells TCF21 promotes increased LRH1 / NR5A2 gene expression by binding to the SHP promoter region, a negative regulator of LRH1. TCF21 is less expressed in adrenocortical carcinoma tumors than in adenomas. In addition, the combined gene expression of TCF21-BUB1B and TCF21-SF1 have prognostic value in adrenocortical tumors of adult and pediatric patients, respectively. Taken together, these data suggest that TCF21 may have a comprehensive role as a regulator of transcription in tumor cells. In this study, we hypothesized that the identification of other targets controlled by TCF21 could contribute to the understanding of their role and importance in tumor cells. The ChIP-Seq method was used to identify 70 target sequences of TCF21 in cells modified to overexpress TCF21 in adrenocortical carcinoma cell line, H295R pCMVMycTCF21 cells. The five most frequent sequences identified were PRDM7, CNTNAP2, CACNA1B, PTPRN2 and KCNE1B genes. Results for qRT-PCR validation showed that TCF21 regulates positively the PRDM7 and CNTNAP2 expression and negatively the CACNA1B expression. In adult and pediatric patients, CACNA1B expression, which codes for the calcium channel Ca v2.2, is higher in carcinomas than in adenomas. However, this increase is not related to overall survival in adult tumors. In addition, selective Ca v2.2 blocking in H295R cells and adult adrenocortical carcinoma cells, ACC-T227, did not alter cell viability. The lack of relationship with overall survival and maintenance of cell viability after Ca v2.2 block suggests that there may be an undetected effect of TCF21 control on Ca v2.2 in adrenocortical tumors. Analysis of the relationship of TCF21 targets observed in hepatocarcinoma samples from patients, using data from The Cancer Genome Atlas Program (TCGA) and validation in HepG2 cells, showed that TCF21 decreases ATP10A gene expression and increases PTPRN2 gene expression in vitro. Our results suggest that the expression of CACNA1B / Ca v2.2 channel may have a differential value and be important in adrenocortical tumorigenesis in adult and pediatric patients, but new approaches and studies are needed. (AU)

• FAPESP's process: 16/12381-7 - Identification of new targets of transcription factor POD1/TCF21 in human tumor cell cultures
• Grantee: Barbara dos Santos Passaia
• Support Opportunities: Scholarships in Brazil - Doctorate