Basic transcription factor 3 (BTF3) regulates transcription of tumor-associated genes in pancreatic cancer cells

Abstract

Basic transcription factor 3 (BTF3) acts as a transcription factor and modulator of apoptosis, and is differentially expressed in colorectal cancer and glioblastomas. In the present study, the expression of BTF3, as well as its role in apoptosis and gene transcription, was analyzed in pancreatic ductal adenocarcinoma (PDAC). QRT-PCR, immunohistochemistry, immunoblotting, and immunofluorescence analyses were carried out to investigate BTF3 mRNA/protein expression and localization. BTF3 silencing in pancreatic cancer cells was performed using specific siRNA molecules. Functional analyses were carried out using cell growth assays, apoptosis assays, and DNA array analysis. BTF3 and BTF3a exhibited 1.3-fold and 4.6-fold increased median mRNA levels in PDAC tissues, compared to normal pancreatic tissues. BTF3 localized mainly in the cytoplasm and nuclei of tubular complexes and pancreatic cancer cells. Pancreatic cancer cell lines expressed the mRNA and protein of BTF3a (27 kDa) and BTF3b (22 kDa) isoforms. BTF3 silencing using specific siRNA molecules did not influence apoptosis induced by chemotherapy or radiotherapy. In contrast, BTF3 silencing resulted in down-regulation of several cancer-associated genes, including EPHB2, ABL2, HPSE2 and ATM, and up-regulation of KRAG, RRAS2, NFkappa-B, MRVI1, MADCAM1 and others. In conclusion, BTF3 is overexpressed in PDAC, where it acts as a transcriptional regulator rather than a direct modulator of apoptosis.