Attenuation of TGF-? signaling suppresses premature senescence in a p21-dependent manner and promotes oncogenic Ras-mediated metastatic transformation in human mammary epithelial cells.

ABSTRACT: The molecular mechanisms that drive triple-negative, basal-like breast cancer progression are elusive. Few molecular targets have been identified for the prevention or treatment of this disease. Here we developed a series of isogenic basal-like human mammary epithelial cells (HMECs) with altered transforming growth factor-? (TGF-?) sensitivity and different malignancy, resembling a full spectrum of basal-like breast carcinogenesis, and determined the molecular mechanisms that contribute to oncogene-induced transformation of basal-like HMECs when TGF-? signaling is attenuated. We found that expression of a dominant-negative type II receptor (DNRII) of TGF-? abrogated autocrine TGF-? signaling in telomerase-immortalized HMECs and suppressed H-Ras-V12-induced senescence-like growth arrest (SLGA). Furthermore, coexpression of DNRII and H-Ras-V12 rendered HMECs highly tumorigenic and metastatic in vivo in comparison with H-Ras-V12-transformed HMECs that spontaneously escaped H-Ras-V12-induced SLGA. Microarray analysis revealed that p21 was the major player mediating Ras-induced SLGA, and attenuated or loss of p21 expression contributed to the escape from SLGA when autocrine TGF-? signaling was blocked in HMECs. Furthermore, knockdown of p21 also suppressed H-Ras-V12-induced SLGA. Our results identify that autocrine TGF-? signaling is an integral part of the cellular anti-transformation network by suppressing the expression of a host of genes, including p21-regulated genes, that mediate oncogene-induced transformation in basal-like breast cancer.

SUBMITTER: Lin S 

PROVIDER: S-EPMC3327327 | biostudies-literature | 2012 Apr

REPOSITORIES: biostudies-literature