A multicenter, single-arm, open-label, phase 2 study of apitolisib (GDC-0980) for the treatment of recurrent or persistent endometrial carcinoma (MAGGIE study).

BACKGROUND: The current single-arm, open-label trial was designed to evaluate the activity of apitolisib (GDC-0980), a dual phosphoinositide 3-kinase/mammalian target of rapamycin (PI3K/mTOR) inhibitor, in patients with advanced endometrial cancer (EC). METHODS: Patients with recurrent or persistent EC who were treated with 1 to 2 prior lines of chemotherapy but no prior PI3K/mTOR inhibitor received oral apitolisib at a dose of 40 mg daily during 28-day cycles until disease progression or intolerable toxicity occurred. Patients with type I/II diabetes who required insulin were excluded. The primary endpoints were progression-free survival (PFS) at 6 months and objective response rate. RESULTS: A total of 56 women were enrolled, including 13 (23%) with well-controlled diabetes. Reasons for discontinuation were disease progression (24 patients; 43%), adverse events (13 patients; 23%), and withdrawal by subject (12 patients; 21%). Grade 3/4 apitolisib-related adverse events were hyperglycemia (46%), rash (30%), colitis (5%), and pneumonitis (4%) (toxicities were graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events [version 4.0]). The PFS rate at 6 months was 20% (Kaplan-Meier estimate; 95% confidence interval [95% CI], 7%-33%). The objective response rate was 6% (confirmed). The median PFS was 3.5 months (95% CI, 2.7-3.7 months) and the median overall survival was 15.7 months (95% CI, 9.2-17.0 months). Nineteen patients discontinued the study before the first tumor assessment. Dose reductions were required for 4 diabetic (31%) and 18 nondiabetic (42%) patients. Comprehensive molecular profiling of 46 evaluable archival tumor samples demonstrated that 57% of patients had at least 1 alteration in phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), phosphatase and tensin homolog (PTEN), or AKT1. All 3 patients with a confirmed response had at least 1 alteration in a PI3K pathway gene. CONCLUSIONS: The antitumor activity noted with the use of a dose of 40 mg of apitolisib daily was limited by tolerability, especially in diabetic patients. Patients with PI3K pathway mutations may have derived enhanced benefit from apitolisib. Cancer 2016;122:3519-28. © 2016 American Cancer Society.

Telaglenastat plus Everolimus in Advanced Renal Cell Carcinoma: A Randomized, Double-Blinded, Placebo-Controlled, Phase II ENTRATA Trial.

PURPOSE: Glutaminase is a key enzyme, which supports elevated dependency of tumors on glutamine-dependent biosynthesis of metabolic intermediates. Dual targeting of glucose and glutamine metabolism by the mTOR inhibitor everolimus plus the oral glutaminase inhibitor telaglenastat showed preclinical synergistic anticancer effects, which translated to encouraging safety and efficacy findings in a phase I trial of 2L+ renal cell carcinoma (RCC). This study evaluated telaglenastat plus everolimus (TelaE) versus placebo plus everolimus (PboE) in patients with advanced/metastatic RCC (mRCC) in the 3L+ setting (NCT03163667). PATIENTS AND METHODS: Eligible patients with mRCC, previously treated with at least two prior lines of therapy [including ≥1 VEGFR-targeted tyrosine kinase inhibitor (TKI)] were randomized 2:1 to receive E, plus Tela or Pbo, until disease progression or unacceptable toxicity. Primary endpoint was investigator-assessed progression-free survival (PFS; one-sided α <0.2). RESULTS: Sixty-nine patients were randomized (46 TelaE, 23 PboE). Patients had a median three prior lines of therapy, including TKIs (100%) and checkpoint inhibitors (88%). At median follow-up of 7.5 months, median PFS was 3.8 months for TelaE versus 1.9 months for PboE [HR, 0.64; 95% confidence interval (CI), 0.34-1.20; one-sided P = 0.079]. One TelaE patient had a partial response and 26 had stable disease (SD). Eleven patients on PboE had SD. Treatment-emergent adverse events included fatigue, anemia, cough, dyspnea, elevated serum creatinine, and diarrhea; grade 3 to 4 events occurred in 74% TelaE patients versus 61% PboE. CONCLUSIONS: TelaE was well tolerated and improved PFS versus PboE in patients with mRCC previously treated with TKIs and checkpoint inhibitors.

Phase I Dose-Escalation Study of Taselisib, an Oral PI3K Inhibitor, in Patients with Advanced Solid Tumors.

Taselisib is a potent and selective tumor growth inhibitor through PI3K pathway suppression. Thirty-four patients with locally advanced or metastatic solid tumors were treated (phase I study, modified 3+3 dose escalation; 5 cohorts; 3-16 mg taselisib once-daily capsule). Taselisib pharmacokinetics were dose-proportional; mean half-life was 40 hours. Frequent dose-dependent, treatment-related adverse events included diarrhea, hyperglycemia, decreased appetite, nausea, rash, stomatitis, and vomiting. At 12 and 16 mg dose levels, dose-limiting toxicities (DLT) were observed, with an accumulation of higher-grade adverse events after the cycle 1 DLT assessment window. Pharmacodynamic findings showed pathway inhibition at ≥3 mg in patient tumor samples, consistent with preclinical PIK3CA-mutant tumor xenograft models. Confirmed response rate was 36% for PIK3CA-mutant tumor patients with measurable disease [5/14: 4 breast cancer (3 patients at 12 mg); 1 non-small cell lung cancer], where responses started at 3 mg, and 0% in patients with tumors without known PIK3CA hotspot mutations (0/15).Significance: Preliminary data consistent with preclinical data indicate increased antitumor activity of taselisib in patients with PIK3CA-mutant tumors (in comparison with patients with tumors without known activating PIK3CA hotspot mutations) starting at the lowest dose tested of 3 mg, thereby supporting higher potency for taselisib against PIK3CA-mutant tumors. Cancer Discov; 7(7); 704-15. ©2017 AACR.See related commentary by Rodon and Tabernero, p. 666This article is highlighted in the In This Issue feature, p. 653.

Identification of an epithelial-specific enhancer regulating ESX expression.

The Ets transcription factor, ESX, exhibits a unique pattern of epithelial-restricted expression and transactivates genes involved in epithelial differentiation and cancer. The aim of this study was to determine the underlying genetic basis for epithelial-specific expression of ESX. We have identified a 30bp ESX enhancer sequence (EES) approximately 3 kb upstream of the proximal promoter. This region displays enhancer activity in an epithelial-specific manner and deletion of this region abrogates ESX gene transcription. An EES binding protein complex (EBC) was identified through electrophoretic mobility shift assays whose degree of EES binding correlated well with endogenous ESX levels in epithelial cells and was regulated by epithelial differentiation. Understanding the regulation of this element will lend insight into mechanisms of epithelial differentiation and the etiology of breast cancer and may provide novel targets for cancer therapeutic intervention.

Estrogen receptor beta inhibits human breast cancer cell proliferation and tumor formation by causing a G2 cell cycle arrest.

Studies indicate that estrogen receptor (ER) alpha mediates breast cancer-promoting effects of estrogens. The role of ERbeta in breast cancer is unknown. Elucidating the role of ERbeta in the pathogenesis of breast cancer is important because many human breast tumors express both ERalpha and ERbeta. We show that adenovirus-mediated expression of ERbeta changes the phenotype of ERalpha-positive MCF-7 cells. Estradiol increases cell proliferation and causes tumor formation of MCF-7 cells expressing only ERalpha. In contrast, introducing ERbeta into MCF-7 cells causes an inhibition of proliferation in vitro and prevents tumor formation in a mouse xenograft model in response to estradiol. ERbeta inhibits proliferation by repressing c-myc, cyclin D1, and cyclin A gene transcription, and increasing the expression of p21(Cip1) and p27(Kip1), which leads to a G(2) cell cycle arrest. These results demonstrate that ERalpha and ERbeta produce opposite effects in MCF-7 cells on cell proliferation and tumor formation. Natural or synthetic ERbeta-selective estrogens may lack breast cancer promoting properties exhibited by estrogens in hormone replacement regimens and may be useful for chemoprevention of breast cancer.

Hyperplasia, reduced E-cadherin expression, and developmental arrest in mammary glands oxidatively stressed by loss of mitochondrial superoxide dismutase.

To investigate the dysregulating effect of excess oxidative stress on mammary gland development, mammary anlage from newborn female mice with normal (+/+) or absent (null, -/-) manganese superoxide dismutase (SOD2) were excised and implanted under the renal capsule of normal host female nude mice with/without concurrent estrogen supplementation. After 30 days the transplanted glands were excised for wholemount, microscopic and immunohistochemical evaluation. In contrast to the normal growth and maturation of transplanted SOD2+/+ glands, SOD2-/- glands showed arrested development, reduced ductal outgrowth and branching, and absent lumen. These hypomorphic SOD2-/- ducts contained hyperplastic epithelium with increased Ki-67 labelling, loss of E-cadherin expression, and disorganized p63 and cytokeratin (K)-14 expressing basal and myoepithelial components. Estrogen treatment failed to upregulate progesterone receptor or normalize development. These findings suggest that excess oxidative stress from loss of SOD2 function can arrest mammary gland maturation and induce hyperplastic epithelium with early premalignant features.

Epithelial-stromal interactions in the mouse and human mammary gland in vivo.

This review deals with the development and hormonal responses of mouse and human mammary glands. A major focus of the review is the role of mesenchymal-epithelial interactions in embryonic mammary development and the role of stromal-epithelial interactions in mammary gland biology. Finally, we present a new model for studying growth, differentiation and hormonal response in human breast epithelium grown in vivo in nude mouse hosts. This new model involves the construction of tissue recombinants composed of human or mouse mammary fibroblasts plus human breast epithelium in polymerized collagen gels. In the model, mouse mammary fibroblasts and human breast fibroblasts appear to support the normal differentiation and growth of human breast epithelium equally. This observation raises the possibility of using mouse mammary fibroblasts from various mutant mice to assess the role of specific paracrine-acting gene products in human mammary gland biology and carcinogenesis.

A novel method for growing human breast epithelium in vivo using mouse and human mammary fibroblasts.

A novel system is described for studying the growth of normal human mammary epithelium in vivo as grafts in athymic nude mice. The key feature of this model is reconstitution of the epithelial-stromal interactions required for normal growth and differentiation of the human mammary epithelium, which produces ducts that are comparable to those in the normal human mammary gland. Human breast epithelial organoids were combined with mammary fibroblasts from mouse or human origin in collagen gels, which were subsequently transplanted under the renal capsule of female nude mice hosts. The resulting grafts showed an increase in the ductal density compared with that observed previously. These ducts expressed appropriate markers for luminal and myoepithelial cells and steroid receptors. Treatment of the host with diethylstilbestrol or estradiol and progesterone significantly increased the number of ducts observed and increased cell proliferation. The grafts also displayed production of beta-casein and milk fat globule membrane protein when the hosts were allowed to become pregnant. This model allows for a variety of epithelial and stromal cells to be used in combination, which would aid in understanding key factors that regulate normal human mammary gland development.