Inhibiting Nuclear Phospho-Progesterone Receptor Enhances Antitumor Activity of Onapristone in Uterine Cancer

Basket study of oral progesterone antagonist onapristone extended release in progesterone receptor-positive recurrent granulosa cell, low-grade serous ovarian cancer, or endometrioid endometrial cancer

OBJECTIVE

To determine the safety and efficacy of the oral progesterone antagonist onapristone extended release (onapristone-XR) in patients with recurrent progesterone receptor (PR)-positive adult-type granulosa cell tumor (aGCT), low-grade serous ovarian cancer (LGSOC), or endometrioid endometrial cancer (EEC).

METHODS

This single-institution phase II study included patients with PR-positive aGCT, LGSOC, or EEC who received ≥1 prior line of chemotherapy. Patients were enrolled from 5/2019-5/2020. PR status was evaluated via immunohistochemistry. Eligible patients had PR expression ≥1% on tissue collected within 3 years of enrollment. Patients received 50 mg of onapristone-XR twice daily until disease progression or treatment discontinuation. Adverse events were graded by Common Terminology Criteria for Adverse Events version 5.0. The primary endpoint was overall response rate (ORR) by Response Evaluation Criteria in Solid Tumors 1.1. Secondary endpoints were response duration, clinical benefit rate (CBR), and safety.

RESULTS

Five patients with LGSOC and 1 with EEC enrolled, but both cohorts closed early due to slow accrual. Fourteen patients with aGCT enrolled and completed stage 1 accrual. No responses were observed. Four patients with LGSOC were evaluable, with median PFS of 4.4 months (range, 1.8-NE) and CBR of 50% (range, 6.8%-93.2%). All 14 patients with aGCT were evaluable, with median PFS of 2.8 months (range, 1.6-4.9), 6-month PFS rate of 21.4% (range, 5.2%-44.8%), 12-month PFS rate of 14.3% (range, 2.3%-36.6%), and a CBR of 35.7% (range, 12.8%-64.9%).

CONCLUSIONS

The study did not meet its primary endpoint. While onapristone-XR was well tolerated in all 3 arms, no objective responses were observed.

Unexplored Functions of Sex Hormones in Glioblastoma Cancer Stem Cells

Biological sex impacts a wide array of molecular and cellular functions that impact organismal development and can influence disease trajectory in a variety of pathophysiological states. In nonreproductive cancers, epidemiological sex differences have been observed in a series of tumors, and recent work has identified previously unappreciated sex differences in molecular genetics and immune response. However, the extent of these sex differences in terms of drivers of tumor growth and therapeutic response is less clear. In glioblastoma (GBM), the most common primary malignant brain tumor, there is a male bias in incidence and outcome, and key genetic and epigenetic differences, as well as differences in immune response driven by immune-suppressive myeloid populations, have recently been revealed. GBM is a prototypic tumor in which cellular heterogeneity is driven by populations of therapeutically resistant cancer stem cells (CSCs) that underlie tumor growth and recurrence. There is emerging evidence that GBM CSCs may show a sex difference, with male tumor cells showing enhanced self-renewal, but how sex differences impact CSC function is not clear. In this mini-review, we focus on how sex hormones may impact CSCs in GBM and implications for other cancers with a pronounced CSC population. We also explore opportunities to leverage new models to better understand the contribution of sex hormones vs sex chromosomes to CSC function. With the rising interest in sex differences in cancer, there is an immediate need to understand the extent to which sex differences impact tumor growth, including effects on CSC function.

Involvement of the Estrogen and Progesterone Axis in Cancer Stemness: Elucidating Molecular Mechanisms and Clinical Significance

Estrogen and progesterone regulate the growth and development of human tissues, including the reproductive system and breasts, through estrogen and progesterone receptors, respectively. These receptors are also important indicators for the clinical prognosis of breast cancer and various reproductive cancers. Many studies have reported that cancer stem cells (CSCs) play a key role in tumor initiation, progression, metastasis, and recurrence. Although the role of estrogen and progesterone in human organs and various cancers has been studied, the molecular mechanisms underlying the action of these hormones on CSCs remain unclear. Therefore, further elucidation of the effects of estrogen and progesterone on CSCs should provide a new direction for developing pertinent therapies. In this review, we summarize the current knowledge on the estrogen and progesterone axis involved in cancer stemness and discuss potential therapeutic strategies to inhibit CSCs by targeting relevant pathways.