Caveolin-1 (P132L), a Common Breast Cancer Mutation, Confers Mammary Cell Invasiveness and Defines a Novel Stem Cell/Metastasis-Associated Gene Signature

Abstract

Here we used the Met-1 cell line in an orthotopic transplantation model in FVB/N mice to dissect the role of the Cav-1(P132L) mutation in human breast cancer. Identical experiments were performed in parallel with wild-type Cav-1. Cav-1(P132L) up-regulated the expression of estrogen receptor-␣ as predicted, because only estrogen receptor-␣-positive patients have been shown to harbor Cav-1(P132L) mutations. In the context of primary tumor formation, Cav-1(P132L) behaved as a loss-of-function mutation, lacking any tumor suppressor activity. In contrast, Cav-1(P132L) caused significant increases in cell migration, invasion, and experimental metastasis, consistent with a gain-of-function mutation. To identify possible molecular mechanism(s) underlying this invasive gain-offunction activity, we performed unbiased gene expression profiling. From this analysis, we show that the Cav-1(P132L) expression signature contains numerous genes that have been previously associated with cell migration, invasion, and metastasis. These include i) secreted growth factors and extracellular matrix proteins (Cyr61, Plf, Pthlh, Serpinb5, Tnc, and Wnt10a), ii) proteases that generate EGF and HGF (Adamts1 and St14), and iii) tyrosine kinase substrates and integrin signaling/adapter proteins (Akap13, Cdcp1, Ddef1, Eps15, Foxf1a, Gab2, Hs2st1, and Itgb4). We and others have shown that the caveolin-1 (Cav-1) gene is commonly mutated in human breast cancers.

Caveolin-1 promotes pancreatic cancer cell differentiation and restores membranous E-cadherin via suppression of the epithelial-mesenchymal transition

“…43 This discrepancy may be explained by the fact that in higher tumor grades Cav-1 loses its tumor suppression role or gains an oncogenic function, potentially by genetic mutations. 44 A biphasic differential expression of Cav-1 was previously suggested in other types of human cancers, including oral cancers, where Cav-1 is highly expressed in early stage disease, but lost in metastatic and advanced lesions. 45 Another possible explanation is that E-cadherin expression is necessary for Cav-1 to act as a tumor suppressor, as E-cadherin pancreatic cancer cells enhanced metastatic potential after orthotopic injection in the pancreas of nude mice and promoted chemoresistance to 5-fluorouracil or gemcitabine.…”

“…Tumor sections were processed as we described before. 44 Briefly, 5 μm sections were prepared from paraffin-embedded tumors. Then, sections were deparaffinized with xylene and rehydrated with graded concentration of ethanol.…”

Caveolin-1 in Melanoma Progression

“…Finally, stromal expression of caveolin-1 in breast cancer predicts outcome, recurrence and survival, further highlighting its relevance as a potential therapeutic target (Sloan, Ciocca et al 2009;Witkiewicz, Dasgupta et al 2009). Indeed, caveolin-1 mutation of P132L, which was previously linked to breast cancer (Hayashi, Matsuda et al 2001), was recently demonstrated to predict recurrence and metastasis in an orthotopic mouse model (Bonuccelli, Casimiro et al 2009). Taken together, these reports demonstrate that caveolin-1 displays traits consistent with a role of the protein as a tumor suppressor.…”

IGF1 dependence of dietary energy balance effects on murine Met1 mammary tumor progression, epithelial-to-mesenchymal transition, and chemokine expression

“…Comparative oncogenomic studies on human and mouse mammary tumors show that tumors from the polyoma middle-T antigen transgenic mice cluster closely with human luminal B breast tumors and share many of the pathological and molecular hallmarks of human luminal B tumors (Herschkowitz et al 2007, Fluck & Schaffhausen 2009, Zhu et al 2011. Furthermore, the Met1 cell line, derived from a spontaneous tumor from a polyoma middle-T antigen transgenic mouse, progressively loses ER and progesterone receptor positivity with tumor progression, therefore providing a rapid and relevant model for studying ERa low luminal mammary tumor progression when orthotopically transplanted into syngeneic mice (Lin et al 2003, Borowsky et al 2005, Namba et al 2006, Bonuccelli et al 2009. Findings from models of luminal A, basal-like, and Her2-positive rodent mammary tumor models (Nickerson et al 1999, Wu et al 2003, Dunlap et al 2012, as well as from a broad spectrum of colon, prostate, pancreatic, skin, and other epithelial cancer models (Moore et al 2008b, Olivo-Marston et al 2009, Lashinger et al 2011, indicate that circulating levels of insulin-like growth factor 1 (IGF1) are central to the dietary energy balance-cancer link.…”