Hypoxia is a state of low oxygen availability that limits tumor growth. The mechanism of protein synthesis inhibition by hypoxia and its circumvention by transformation are not well understood. Hypoxic breast epithelial cells are shown to downregulate protein synthesis by inhibition of the kinase mTOR, which suppresses mRNA translation through a novel mechanism mitigated in transformed cells: disruption of proteasome-targeted degradation of eukaryotic elongation factor 2 (eEF2) kinase and activation of the regulatory protein 4E-BP1. In transformed breast epithelial cells under hypoxia, the mTOR and S6 kinases are constitutively activated and the mTOR negative regulator tuberous sclerosis complex 2 (TSC2) protein fails to function. Gene silencing of 4E-BP1 and eEF2 kinase or TSC2 confers resistance to hypoxia inhibition of protein synthesis in immortalized breast epithelial cells. Breast cancer cells therefore acquire resistance to hypoxia by uncoupling oxygen-responsive signaling pathways from mTOR function, eliminating inhibition of protein synthesis mediated by 4E-BP1 and eEF2.

Secretory carcinoma of the breast is a rare breast cancer that is associated with incidence at a young age and an indolent course. The role for breast conservation and adjuvant radiation is unknown. The SEER database was reviewed and 83 patients were identified with secretory carcinoma of the breast between the years 1983 and 2007. Baseline characteristics were compared with χ(2) or Fisher's exact test. Overall survival (OS) and cause-specific survival (CSS) were estimated using the Kaplan-Meier method. Analyses were performed using PASW Statistics, version 18. Median follow-up was 70 months. Median patient age was 53 years (range 11-86 years). 29 patients (34.9%) had involved regional lymph nodes. 39 patients (47.0%) underwent lumpectomy and 44 patients (53.0%) underwent mastectomy. 35 patients (42.2%) received radiation. Patients receiving radiation were more likely to have undergone lumpectomy, and the use of radiation increased over time. 5-year OS was 87.2%; 10-year OS was 76.5%. 5-year CSS was 94.4%; 10-year CSS was 91.4%. Among the lumpectomy patients, 25 patients (64.1%) received radiation. For lumpectomy patients, those who did not receive radiation had a 5-year OS of 92.9% and 10-year OS of 72.2% while patients who did receive radiation had a 5-year OS of 95.5% and 10-year OS of 85.9%. Only 1 patient treated with lumpectomy only died of cancer (92.9% CSS) and no patients treated with lumpectomy and radiation died of cancer (100% CSS). Secretory carcinoma of the breast commonly occurs at a later age than previously recognized, and is associated with good long-term survival.

A subset of obese humans has relatively low plasma levels of leptin. This finding has suggested that in some cases abnormal regulation of the leptin gene in adipose tissue is etiologic in the pathogenesis of the obese state. The possibility that a relative decrease in leptin production can lead to obesity was tested by mating animals carrying a weakly expressed adipocyte specific aP2-human leptin transgene to C57BL/6J ob/ob mice (which do not express leptin). The transgene does not contain the regulatory elements of the leptin gene and is analogous to a circumstance in which the cis elements and/or trans factors regulating leptin RNA production are abnormal. The ob/ob mice carrying the transgene had a plasma leptin level of 1.78 ng/ml, which is ≈one-half that found in normal, nontransgenic mice (3.72 ng/ml, P < 0.01). The ob/ob animals expressing the leptin transgene were markedly obese though not as obese as ob/ob mice without the transgene. The infertility as well as several of the endocrine abnormalities generally evident in ob/ob mice were normalized in the ob/ob transgenic mice. However, the ob/ob transgenic mice had an abnormal response when placed at an ambient temperature of 4°C, suggesting that different thresholds exist for the different biologic effects of leptin. Leptin treatment of the ob/ob transgenic mice resulted in marked weight loss with efficacy similar to that seen after treatment of wild-type mice. In aggregate these data suggest that dysregulation of leptin gene can result in obesity with relatively normal levels of leptin and that this form of obesity is responsive to leptin treatment.