Abstract Background Depatuxizumab mafodotin (Depatux-M) is a tumor-specific antibody–drug conjugate consisting of an antibody (ABT-806) directed against activated epidermal growth factor receptor (EGFR) and the toxin monomethylauristatin-F. We investigated Depatux-M in combination with temozolomide or as a single agent in a randomized controlled phase II trial in recurrent EGFR amplified glioblastoma. Methods Eligible were patients with centrally confirmed EGFR amplified glioblastoma at first recurrence after chemo-irradiation with temozolomide. Patients were randomized to either Depatux-M 1.25 mg/kg every 2 weeks intravenously, or this treatment combined with temozolomide 150–200 mg/m2 day 1–5 every 4 weeks, or either lomustine or temozolomide. The primary endpoint of the study was overall survival. Results Two hundred sixty patients were randomized. In the primary efficacy analysis with 199 events (median follow-up 15.0 mo), the hazard ratio (HR) for the combination arm compared with the control arm was 0.71 (95% CI = 0.50, 1.02; P = 0.062). The efficacy of Depatux-M monotherapy was comparable to that of the control arm (HR = 1.04, 95% CI = 0.73, 1.48; P = 0.83). The most frequent toxicity in Depatux-M treated patients was a reversible corneal epitheliopathy, occurring as grades 3–4 adverse events in 25–30% of patients. In the long-term follow-up analysis with median follow-up of 28.7 months, the HR for the comparison of the combination arm versus the control arm was 0.66 (95% CI = 0.48, 0.93). Conclusion This trial suggests a possible role for the use of Depatux-M in combination with temozolomide in EGFR amplified recurrent glioblastoma, especially in patients relapsing well after the end of first-line adjuvant temozolomide treatment. (NCT02343406)

Prostate cancer is an important public health problem in the United States. Seven phytoestrogens found in common herbal products were screened for estrogen receptor binding and growth inhibition of androgen-insensitive (PC-3) and androgen-sensitive (LNCaP) human prostate tumor cells. In a competitive 3H-estradiol ligand binding assay using mouse uterine cytosol, 2.5 M quercetin, baicalein, genistein, epigallocatechin gallate (EGCG), and curcumin displaced > 85% of estradiol binding, whereas apigenin and resveratrol displaced > 40%. From growth inhibition studies in LNCaP cells, apigenin and curcumin were the most potent inhibitors of cell growth, and EGCG and baicalein were the least potent. In PC-3 cells, curcumin was the most potent inhibitor of cell growth, and EGCG was the least potent. In both cell lines, significant arrest of the cell cycle in S phase was induced by resveratrol and EGCG and in G2M phase by quercetin, baicalein, apigenin, genistein, and curcumin. Induction of apoptosis was induced by all of the 7 compounds in the 2 cell lines as shown by TUNEL and DNA fragmentation assays. Androgen responsiveness of the cell lines did not correlate with cellular response to the phytoestrogens. In conclusion, these 7 phytoestrogens, through different mechanisms, are effective inhibitors of prostate tumor cell growth.

Understanding estrogen's regulation of phase II detoxification enzymes is important in explaining how estrogen exposure increases the risk of developing certain cancers. Phase II enzymes such as glutathione-S-transferases (GST) and quinone reductase protect against developing chemically induced cancers by metabolizing reactive oxygen species. Phase II enzyme expression is regulated by a cis-acting DNA sequence, the antioxidant response element (ARE). It has previously been reported that several antiestrogens, but not 17beta-estradiol, could regulate ARE-mediated gene transcription. Our goal was to determine whether additional estrogenic compounds could regulate ARE-mediated gene expression both in vitro and in vivo. We discovered that physiological concentrations (10 nm) of 17beta-estradiol repressed GST Ya ARE-dependent gene expression in vitro. Treatment with other endogenous and anti-, xeno-, and phytoestrogens showed that estrogen receptor/ARE signaling is ligand, receptor subtype, and cell type specific. Additionally, GST and quinone reductase activities were significantly lowered in a dose-dependent manner after 17beta-estradiol exposure in the uteri of mice. In conclusion, we have shown that 17beta-estradiol, and other estrogens, down-regulate phase II enzyme activities. We propose estrogen-mediated repression of phase II enzyme activities may increase cellular oxidative DNA damage that ultimately can result in the formation of cancer in some estrogen-responsive tissues.

The HER2 proto-oncogene, a member of the epidermal growth factor receptor family, is overexpressed in 20-30% of breast cancers. Genistein, the main soy isoflavone, interacts with estrogen receptors (ER) and it is also a potent tyrosine kinase inhibitor. Previously, our laboratory found that genistein delayed mammary tumor onset in transgenic mice that overexpress HER2 gene. Our goal was to define the mechanism through which genistein affects mammary tumorigenesis in HER2 overexpressing mice. We hypothesized that genistein inhibits HER2 activation and expression through ER-dependent and ER-independent mechanisms. Genistein inhibited total HER2 protein expression and tyrosine phosphorylation in BT-474, an ERalpha (-) and ERbeta (+) human breast cancer cell line, however, E2 had no effect. Taken together, these data suggest that genistein has an ER-independent inhibitory effect, presumably, through tyrosine kinase inhibition activity. Genistein at 1.0 microM mimicked E2 and down-regulated HER2 protein phosphorylation when BT-474 was co-transfected with ERalpha, but not ERbeta. Although E2 and overexpression of HER2 can promote mammary tumorigenesis, an inverse relationship between ER expression and HER2 overexpression has been found in human breast cancer. We cloned a 500-bp promoter region upstream of the HER2 transcription initiation site. Co-transfection with ERalpha, but not with ERbeta, down-regulated HER2 promoter reporter in BT-474. At concentrations > or =1 microM, genistein inhibited HER2 promoter reporter in the absence of ERalpha. In conclusion, genistein at > or =1 microM inhibited HER2 protein expression, phosphorylation, and promoter activity through an ER-independent mechanism. In the presence of ERalpha, genistein mimicked E2 and inhibited HER2 protein phosphorylation. These data support genistein's chemo-prevention and potential chemo-therapeutic roles in breast cancer.

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