RhoC GTPase Overexpression Modulates Induction of Angiogenic Factors in Breast Cells

Abstract

Inflammatory breast cancer (IBC) is a distinct and aggressive form of locally advanced breast cancer. IBC is highly angiogenic, invasive, and metastatic at its inception. Previously, we identified specific genetic alterations of IBC that contribute to this highly invasive phenotype. RhoC GTPase was overexpressed in 90% of archival IBC tumor samples, but not in stage-matched, non-IBC tumors. To study the role of RhoC GTPase in contributing to an IBC-like phenotype, we generated stable transfectants of human mammary epithelial cells overexpressing the RhoC gene, and studied the effect of RhoC GTPase overexpression on the modulation of angiogenesis in IBC. Levels of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), interleukin-6 (IL-6), and interleukin-8 (IL-8) were significantly higher in the conditioned media of the HME-RhoC transfectants than in the untransfected HME and HME-beta-galactosidase control media, similar to the SUM149 IBC cell line. Inhibition of RhoC function by introduction of C3 exotransferase decreased production of angiogenic factors by the HME-RhoC transfectants and the SUM149 IBC cell line, but did not affect the control cells. These data support the conclusion that overexpression of RhoC GTPase is specifically and directly implicated in the control of the production of angiogenic factors by IBC cells.

Genomic analysis reveals RhoC as a potential marker in hepatocellular carcinoma with poor prognosis

“…For instance, overexpression of RhoC was found in metastatic lesions of inflammatory breast cancer and pancreatic ductal adenocarcinoma (Suwa et al, 1998;Fritz et al, 2002;Kleer et al, 2002), and upregulation was associated with tumour progression in ovarian carcinoma (Horiuchi et al, 2003). While the molecular mechanism by which RhoC facilitates tumour metastasis remains to be determined, it is possible that increased expression of RhoC could result in: (1) disruption of cell polarity, which plays an important role in the epithelial -mesenchymal transition observed in more aggressive tumours (Zondag et al, 2000); (2) contribution to the loss of adherens junctions (Braga et al, 2000); (3) increase motility and ability to remould the extra-cellular matrix, which is required for tumour cells to become locally invasive (Khanna et al, 2001); and (4) increase in angiogenic factors that would result in promotion of vascularisation in tumour and increase the likelihood of tumour cell entering the bloodstream (van Golen et al, 2000).…”

Regulation of Inflammatory Breast Cancer Cell Invasion through Akt1/PKBα Phosphorylation of RhoC GTPase

“…The SUM149s are a reliable model of IBC, often reflecting what is observed in patient samples (11,12,17,(26)(27)(28)(29)(30)(31). Figure 2A is western blot analysis of individual Akt isoform protein expression and phosphorylation.…”

“…RhoC GTPase overexpression leads to transformation of immortalized human mammary epithelial cells with an invasive phenotype similar to that of IBC (17). RhoC also promotes metastasis in other invasive cancers, including pancreatic ductal adenocarcinoma (18), lung cancer (19), and melanoma (20).…”

Deregulation of the Rho GTPase, Rac1, suppresses cyclin-dependent kinase inhibitor p21CIP1 levels in androgen-independent human prostate cancer cells

“…Moreover, stable overexpression of RhoC confers a malignant phenotype to otherwise nontransformed human mammary epithelial cells (van Golen et al, 2000). Mira et al (2000) demonstrated that Rac3 is hyperactive in rapidly proliferating breast cancer cells, where it appears to be necessary for G1 to S phase transition.…”