αB-Crystallin is a novel oncoprotein that predicts poor clinical outcome in breast cancer
Jose V. Moyano, … , Charles M. Perou, Vincent L. Cryns
Jose V. Moyano, … , Charles M. Perou, Vincent L. Cryns
Published January 4, 2006
Citation Information: J Clin Invest. 2006;116(1):261-270. https://doi.org/10.1172/JCI25888.
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Research Article Oncology

αB-Crystallin is a novel oncoprotein that predicts poor clinical outcome in breast cancer

Abstract

Recent gene profiling studies have identified a new breast cancer subtype, the basal-like group, which expresses genes characteristic of basal epithelial cells and is associated with poor clinical outcomes. However, the genes responsible for the aggressive behavior observed in this group are largely unknown. Here we report that the small heat shock protein α-basic–crystallin (αB-crystallin) was commonly expressed in basal-like tumors and predicted poor survival in breast cancer patients independently of other prognostic markers. We also demonstrate that overexpression of αB-crystallin transformed immortalized human mammary epithelial cells (MECs). In 3D basement membrane culture, αB-crystallin overexpression induced luminal filling and other neoplastic-like changes in mammary acini, while silencing αB-crystallin by RNA interference inhibited these abnormalities. αB-Crystallin overexpression also induced EGF- and anchorage-independent growth, increased cell migration and invasion, and constitutively activated the MAPK kinase/ERK (MEK/ERK) pathway. Moreover, the transformed phenotype conferred by αB-crystallin was suppressed by MEK inhibitors. In addition, immortalized human MECs overexpressing αB-crystallin formed invasive mammary carcinomas in nude mice that recapitulated aspects of human basal-like breast tumors. Collectively, our results indicate that αB-crystallin is a novel oncoprotein expressed in basal-like breast carcinomas that independently predicts shorter survival. Our data also implicate the MEK/ERK pathway as a potential therapeutic target for these tumors.

Authors

Jose V. Moyano, Joseph R. Evans, Feng Chen, Meiling Lu, Michael E. Werner, Fruma Yehiely, Leslie K. Diaz, Dmitry Turbin, Gamze Karaca, Elizabeth Wiley, Torsten O. Nielsen, Charles M. Perou, Vincent L. Cryns

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Figure 2

αB-Crystallin overexpression disrupts mammary acinar morphology.

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The neoplastic abnormalities in mammary acini overexpressing αB-crystall...
(A) Immunoblot of day-12 acini formed by parental MCF-10A cells and MCF-10A pools (pLXSN, αB-WT, and αB-3XSE). αB, αB-crystallin. (B) Phase contrast images of day-12 acini formed by parental MCF-10A cells, MCF-10A pools, or an MCF-12A pool stably expressing αB-WT. (C) Day-12 acini formed by parental MCF-10A cells or pools were scored for abnormal morphology (enlarged structures with filled lumens), diameter, and cell number per cross section (mid-acini). (D) Silencing αB-crystallin in MCF-10A–αB-WT cells by RNAi suppressed the abnormal morphology of αB-WT acini. (E) Day-12 pLXSN, αB-WT, or αB-3XSE acini were immunostained with antibodies to αB-crystallin (green) and GM130, an apical marker of polarized epithelium (red, upper panels), or the integrin β4 subunit, a basolateral marker (red, lower panels). Confocal images of mid-acini cross sections are shown. Inset: Higher magnification of the same acinus (magnified ×2.5 of original). (F) Percentage of day-12 acini with polarized epithelium. (G) pLXSN, αB-WT, and αB-3XSE acini were immunostained with antibodies to αB-crystallin and active caspase-3 (upper panels, day 8) or Ki-67 (lower panels, day 12). (H) Percentage of acini that contained ≥2 cells positive for active caspase-3 (day 8) or Ki-67 (day 12). In A–H, data are mean ± SD (n = 3, except RNAi in D and laminin-5 polarity in F, which were n = 2, each in duplicate). *P < 0.05 versus control; ***P < 0.001 versus pLXSN. Scale bars: 100 μm (B and D); 50 μm (E and G).