Onvansertib Induces Preclinical Anti-Tumorigenic Effects in Endometrioid Endometrial Cancer

Nikita Sinha, MD

The targeting agent onvansertib exhibited anti-tumorigenic and anti-proliferative effects in endometrioid endometrial cancer, according to data from a preclinical investigation presented at the 2024 SGO Winter Meeting.

In endometrial cancer cell lines that were exposed to onvansertib at varying concentrations via various assays, the investigative agent, which has elicited beneficial data in other disease histologies, impeded cellular proliferation, thereby prompting cell cycle arrest and apoptosis, elevating cellular stress, and hindering cellular adhesion.

“Our results are exciting and show potential benefit from using onvansertib in endometrioid endometrial cancer,” Nikita Sinha, MD, explained in an interview with OncLive®. “We’re seeing in this cellular work a significant anti-tumorigenic and anti-proliferative effect from how [onvansertib] inhibits cellular proliferation; induces cell cycle arrest and apoptosis; and increases cellular stress and impaired cellular adhesion.”

In the interview, Sinha discussed the effects of onvansertib on cellular proliferation, adhesion, apoptosis, and stress in endometrial cancer cells that were derived from preclinical models of endometrioid endometrial cancer, highlighting the potential future uses of the agent in this patient population. Sinha is a gynecologic oncology fellow in the Department of Obstetrics at the University of North Carolina (UNC) at UNC Chapel Hill, UNC School of Medicine.

OncLive: What served as the objective for launching research on the use of onvansertib in endometrial cancer?

Sinha: Endometrial cancer is the fourth most common cancer among women in the United States, and it continues to increase in frequency and mortality due to the obesity epidemic, which emphasizes the need for us to develop novel treatments for patients with endometrial cancer.

Plk1 is known to play an integral role in cell division, and it’s overexpressed in many different cancers including endometrial cancer. Plk1 is a downstream target in the AKT/mTOR pathway, which is frequently altered in endometrial cancer. What we’ve seen in other cancer types is that targeting Plk1 leads to mitotic cell cycle arrest, causes apoptosis, and reduces tumor growth in preclinical models of ovarian cancer and breast cancer. [The Plk1 inhibitor onvansertib is] being evaluated in phase 1 and 2 trials for breast and lung cancer, but there are no data with it in endometrial cancer.

Therefore, our objective was to investigate the effects of onvansertib and targeting Plk1 on cell proliferation, apoptosis, cellular stress, adhesion, and invasion in endometrial cancer cells.

What methods were used to conduct this study?

We studied onvansertib in human endometrioid endometrial cancer cell lines, which included KLE and EC-023. We exposed these cells to onvansertib at varying concentrations and assessed its activity via a few different assays. We evaluated cell proliferation by the MTT and colony count assays; we investigated apoptosis by the Cleaved Caspase-3 assay; and we assessed cellular stress by a reactive oxygen species and JC-1 assays.

We evaluated the impact of onvansertib on cellular adhesion using laminins, evaluated cellular migration using a wound healing assay, and used Western immunoblotting to assess onvansertib’s effects on downstream targets related to cellular stress, apoptosis, cellular invasion, cell cycle control, and DNA damage.

What findings from this research were presented at the 2024 SGO Winter Meeting?

We found that onvansertib has anti-tumorigenic effects on endometrioid endometrial cancer cell lines. Onvansertib inhibited cellular proliferation in a dose-dependent manner in both the KLE and EC-023 cell lines. The colony count was also reduced with increasing doses of onvansertib in both cell lines.

When we treated cells with onvansertib for 12 hours, [the agent] significantly increased Cleaved Caspase-3 activity in both cell lines, indicating that there was increased apoptosis of both types of cells. Onvansertib [treatment] correlated with the downregulated expression of anti-apoptotic proteins, such as MCL1 and BCL-2, as well as upregulated, pro-apoptotic proteins, such as BAX.

When we evaluated cellular stress, treatment of the cells with increasing doses of onvansertib significantly increased reactive oxygen species production by between 12% and 16% in the KLE and EC-023 cells and decreased mitochondrial membrane potential in a dose-dependent manner, between 15% and 18% for both cell lines.

On the protein level, onvansertib increased [the prevalence of] cellular stress proteins, such as BIP, Calnexin, and ATF-4, corresponding with the effect we saw in the assays evaluating cellular stress. When we investigated cellular migration, onvansertib effectively reduced the adhesive ability of both endometrioid endometrial cancer cell lines and inhibited the capacity of cell migration. We also saw that onvansertib downregulated proteins that are important for cellular adhesion and migration, such as N-cadherin and B-catenin, and upregulated E-cadherin.

Diving into the mechanism of how onvansertib was working, cell cycle assays [revealed] that onvansertib resulted in a G2 phase arrest in both cell lines, so the cells found in the G2 phase increased significantly. Corresponding with that, [with onvansertib treatment], we saw downregulated expression of important cell cycle proteins, such as CDK4, c-myc, and CDK2.

Lastly, similar to what’s been done in other cancer cell lines, we studied a combination treatment using both onvansertib and paclitaxel, finding that both agents used together increased cellular stress in a synergistic fashion. All those results were promising in showing the anti-tumorigenic and anti-proliferative effects in these endometrioid endometrial cancer cell lines.

How did these results compare with the preclinical and clinical data that have been seen with the agent in other tumor types?

We hypothesized that we would see the [observed] effect of onvansertib in endometrioid endometrial cancer given the targeted pathways that Plk1 is involved in. We’ve been impressed by the promising degree of response seen on the cellular level. Interestingly, the synergistic response we saw with [onvansertib and] paclitaxel was similar to [that with the combination in] other cancer types.

What are the next steps for this research?

We’re already starting to use onvansertib in a mouse model of endometrioid endometrial cancer to see whether treatment with this drug reduces tumor growth size in mice. If we continue to see promising preclinical results in mice, the next step would be moving toward a phase 1 clinical trial using this agent either alone or in combination with other chemotherapeutic agents in patients with endometrioid endometrial cancer.

What would you like your colleagues to take away from this research?

Given these promising initial preclinical results, my colleagues should watch out for this agent in the future, because as further studies evaluate the clinical translatability of this agent, it could have a lot of benefit for our patients with endometrioid endometrial cancer.

Reference

Sinha N, Shen X, Haag J, et al. Onvansertib exhibits anti-tumorigenic effects in pre-clinical models of endometrioid endometrial cancer. Presented at: SGO Winter Meeting; January 25-27, 2024; Olympic Valley, CA. Poster 492352.