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Fhit Nuclear Import Following EGF Stimulation Sustains Proliferation of Breast Cancer Cells
Author(s) -
Bianchi Francesca,
Sasso Marianna,
Turdo Federica,
Beretta Giovanni L.,
Casalini Patrizia,
Ghirelli Cristina,
Sfondrini Lucia,
Ménard Sylvie,
Tagliabue Elda,
Campiglio Manuela
Publication year - 2015
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.24968
Subject(s) - fhit , cell growth , nuclear localization sequence , cancer research , nuclear export signal , nuclear protein , biology , cytoplasm , microbiology and biotechnology , cell nucleus , cancer cell , transfection , proteasome , stimulation , cell , cell culture , chemistry , cancer , tumor suppressor gene , carcinogenesis , endocrinology , biochemistry , genetics , gene , transcription factor
The tumor‐suppressor protein fragile histidine triad (Fhit) exerts its functions in the cytoplasm, although some reports suggest that it may also act in the nucleus. We previously showed that cytosolic Fhit protein levels in cancer cell lines stimulated to proliferate were reduced by proteasomal degradation. Here, we demonstrate that Fhit is physiologically present in the nucleus of breast cancer cell lines and tissues at a low level and that proliferative stimulation increases nuclear levels. Breast cancer cells expressing the FhitY114F mutant, which do not undergo proteasomal degradation, contained mutated Fhit in the nucleus, while cells treated with a proteasome inhibitor accumulated nuclear Fhit during proliferation. Thus, Fhit nuclear shuttling and proteasome degradation phenomena occur independently. When Fhit was coupled to a nuclear localization sequence, the proliferation rate of the transfected cells increased together with levels of proliferation pathway mediators cyclin D1, phospho‐MAPK, and phospho‐STAT3. Fhit nuclear translocation upon mitogenic stimulation may represent a new regulatory mechanism that allows rapid restoration of Fhit cytoplasmic levels and promotes the proliferation cascade activated by mitogenic stimulation. J. Cell. Physiol. 9999: 2661–2670, 2015. © 2015 Wiley Periodicals, Inc.