Polymerase Ѳ inhibitors combinations with approved and investigational agents in patient-derived tumor multi-cell type (mct) spheroids

Beverly A Teicher; Thomas S Dexheimer; Li Chen; Thomas Silvers; Eric M Jones; Nathan P Coussens; J Paul Eder; James H Doroshow

doi:10.1016/j.yexmp.2025.104978

Polymerase Ѳ inhibitors combinations with approved and investigational agents in patient-derived tumor multi-cell type (mct) spheroids

Exp Mol Pathol. 2025 Jun 27:143:104978. doi: 10.1016/j.yexmp.2025.104978. Online ahead of print.

Authors

Beverly A Teicher¹, Thomas S Dexheimer², Li Chen², Thomas Silvers², Eric M Jones², Nathan P Coussens², J Paul Eder³, James H Doroshow⁴

Affiliations

¹ Division of Cancer Treatment and Diagnosis, National Cancer Institute, Bethesda, MD 20892, United States of America. Electronic address: Beverly.Teicher@nih.gov.
² Applied and Developmental Research Directorate, Frederick National Laboratory for Cancer Research, Frederick, MD 21702, United States of America.
³ Yale University School of Medicine, New Haven, CT 06510, United States of America.
⁴ Division of Cancer Treatment and Diagnosis, National Cancer Institute, Bethesda, MD 20892, United States of America.

PMID: 40580893
DOI: 10.1016/j.yexmp.2025.104978

Abstract

The potential of novobiocin, recently identified to be a DNA POLѲ inhibitor, to augment cancer chemotherapy was explored in the late 1980s and early 1990s in tumor cells, tumor-bearing mice and in Phase 1 clinical trial in combination with cyclophosphamide or cisplatin. Genetic alterations which may increase or decrease POLѲ inhibitor effects have been elucidated. Thirty patient-derived tumor cell lines with known BRCA, ATM, ATR, POLѲ, XRCC1, PALB2, PARP1, LIG3 alterations as well as know gLOH% and MSI status were screened in a mct-spheroid assay (tumor cells, endothelial cells, mesenchymal stem cells) with a POLѲ inhibitor, novobiocin, ART-558, and RP6685, alone or in simultaneous combination with a FDA-approved or investigational anticancer small molecule with a 7-day exposure and a CellTiter-Glo 3D luminescence endpoint. As single agents, the POLѲ inhibitors had little or no cytotoxicity. In simultaneous combination with ART-558, talazoparib produced greater-than-additive cytotoxicity at the highest concentrations of the POLѲ inhibitors in the 922,993-354-T-J3-PDC endometrial serous carcinoma mct-spheroids. Activity of the Chk1/2 inhibitor prexasertib was potentiated by either ART-558 or RP6685 in the 922,993-354-T-J3 mct-spheroids. The combination of POLѲ inhibitors ART-558 and RP6685, and the Chk1/2 inhibitor prexasertib produced up to 1 log increase in cytotoxicity in the 922,993-354-T-J3 mct-spheroids. Regions of potentiation were evident in the 922,993-354-T-J3-PDC endometrial carcinoma survival surface plots at the highest concentration of paclitaxel tested, while regions of potentiation were evident in the paclitaxel mid-concentrations of the 299,254-011-R-J1-PDC melanoma mct-spheroids survival surface plots as determined by the Bliss independence calculation. DNA POLѲ is recruited to DNA double-strand breaks as a component of repair. POLѲ allosteric inhibitors, novobiocin, ART558 and RP-6685, have entered clinical trial. The current study explores the cytotoxicity of POLѲ inhibitors in combination with anticancer drugs and investigational agents in patient-derived cell lines grown as mct-spheroids.

Keywords: 3D culture model; Combination screening; DNA polymerase inhibitors; Spheroids.