No abstract

Canonical Wnt signaling regulates the transcription of T-cell factor (TCF)-responsive genes through the stabilization and nuclear translocation of the transcriptional co-activator, β-catenin. Overexpression of β-catenin features prominently in acute myeloid leukemia (AML) and has previously been associated with poor clinical outcome. Overexpression of γ-catenin mRNA (a close homologue of β-catenin) has also been reported in AML and has been linked to the pathogenesis of this disease, however, the relative roles of these catenins in leukemia remains unclear. Here we report that overexpression and aberrant nuclear localization of γ-catenin is frequent in AML. Significantly, γ-catenin expression was associated with β-catenin stabilization and nuclear localization. Consistent with this, we found that ectopic γ-catenin expression promoted the stabilization and nuclear translocation of β-catenin in leukemia cells. β-Catenin knockdown demonstrated that both γ- and β-catenin contribute to TCF-dependent transcription in leukemia cells. These data indicate that γ-catenin expression is a significant factor in the stabilization of β-catenin in AML. We also show that although normal cells exclude nuclear translocation of both γ- and β-catenin, this level of regulation is lost in the majority of AML patients and cell lines, which allow nuclear accumulation of these catenins and inappropriate TCF-dependent transcription.

Activated Src kinase may contribute to the progression and spread of breast cancers and recent in vitro evidence suggests a role for Src in acquired endocrine resistance. The purpose of this study was to investigate whether modulation of Src activity in endocrine-sensitive and endocrine-resistant breast cancer cells directly affected their phenotype and sensitivity to 4-hydroxy Tamoxifen (tamoxifen) and to determine whether Src activity in breast cancer tissue affected patient outcome. Expression of constitutively active Src in ER-positive, endocrine-sensitive MCF7 breast cancer cells resulted in the development of an aggressive phenotype, akin to that previously observed in cell models of Tamoxifen resistance, and, significantly, attenuated their response to tamoxifen. Conversely, expression of dominant negative-Src in tamoxifen-resistant MCF7 cells resensitized them to tamoxifen. An exploratory immunohistochemical study of an archival primary breast tumor series (n = 75) with parallel clinicopathological data and in normal breast tissues (n = 19) revealed higher levels of activated Src in the cytoplasm (p < 0.01) and lower levels of nuclear Src (p < 0.01) in tumor tissue compared with normal tissue. Whereas elevated levels of activated-Src in the cytoplasm of tumors was significantly associated with reduced survival in ER+ patients (p = 0.031), elevated levels of activated Src within the nucleus appeared to associate with an improved hormonal response. Together these data are further suggestive of a role for Src in breast cancer where it may alter response to endocrine therapy.

Background The marked differences in the incidences of both breast and prostate cancer between the East and the West have been attributed to habitual diet. Traditionally, Japanese and Far Eastern people in general consume large quantities of soya and soya-derived foodstuffs. Diphenolic soya phytoestrogens have weak oestrogenic and anti-oestrogenic properties and have been implicated in preventing or limiting the early processes associated with breast and prostate carcinogenesis.