Can phosphatidylinositol 3-kinase/mammalian target of rapamycin inhibition ERase them all?

An Update on Tamoxifen and the Chemo-Preventive Potential of Vitamin E in Breast Cancer Management

Breast cancer (BC) is the most common female cancer in terms of incidence and mortality worldwide. Tamoxifen (Nolvadex) is a widely prescribed, oral anti-estrogen drug for the hormonal treatment of estrogen-receptor-positive BC, which represents 70% of all BC subtypes. This review assesses the current knowledge on the molecular pharmacology of tamoxifen in terms of its anticancer and chemo-preventive actions. Due to the importance of vitamin E compounds, which are widely taken as a supplementary dietary component, the review focuses only on the potential importance of vitamin E in BC chemo-prevention. The chemo-preventive and onco-protective effects of tamoxifen combined with the potential effects of vitamin E can alter the anticancer actions of tamoxifen. Therefore, methods involving an individually designed, nutritional intervention for patients with BC warrant further consideration. These data are of great importance for tamoxifen chemo-prevention strategies in future epidemiological studies.

Mouse models of PIK3CA mutations: one mutation initiates heterogeneous mammary tumors

The phosphoinositide 3-kinase (PI3K) signaling pathway is crucial for cell growth, proliferation, metabolism, and survival, and is frequently deregulated in human cancer, including ~ 70% of breast tumors. PIK3CA, the gene encoding the catalytic subunit p110α of PI3K, is mutated in ~ 30% of breast cancers. However, the exact mechanism of PIK3CA-evoked breast tumorigenesis has not yet been defined. Genetically engineered mouse models are valuable for examining the initiation, development and progression of cancer. Transgenic mice harboring hotspot mutations in p110α have helped to elucidate breast cancer pathogenesis and increase our knowledge about molecular and cellular alterations in vivo. They are also useful for the development of therapeutic strategies. Here, we describe current mouse models of mutant PIK3CA in the mammary gland, and discuss differences in tumor latency and pathogenesis.

Luminal expression of PIK3CA mutant H1047R in the mammary gland induces heterogeneous tumors

The phosphoinositide 3-kinase (PI3K) signaling cascade, a key mediator of cellular survival, growth, and metabolism, is frequently altered in human cancer. Activating mutations in PIK3CA, which encodes the α-catalytic subunit of PI3K, occur in approximately 30% of breast cancers. These mutations result in constitutive activity of the enzyme and are oncogenic, but it is not known whether they are sufficient to induce mammary carcinomas in mice. In the present study, we show that the expression of mutant PIK3CA H1047R in the luminal mammary epithelium evokes heterogeneous tumors that express luminal and basal markers and are positive for the estrogen receptor. Our results suggest that the PIK3CA H1047R oncogene targets a multipotent progenitor cell and, furthermore, show that this model recapitulates features of human breast tumors with PIK3CA H1047R.