iNOS-Produced Nitric Oxide from Cancer Cells as an Intermediate of Stemness Regulation by PARP-1 in Colorectal Cancer Moral Martínez, María del Sánchez-Uceta, Paula Clemente González, Rubén San Juan, Sara Moreno Puentes Pardo, José David Khaldy, Huda López Pérez, David Arnedo Fernández, Francisco Javier Casado, Jorge Martínez Heredia, Luis Carazo, Ángel León, Josefa Colorectal cancer (CRC) PARP1 iNOS This work was supported by a research grant from the Instituto de Salud Carlos III-FEDER (PI21/01378) and the Consejería de Salud from the Junta de Andalucía (PI-067/2013). J.L. was supported by the Nicolás Monardes Program from the Andalusian Health Service (C-0033-2015). P.S.-U. is funded by a predoctoral fellowship (FI23/00234) from the Instituto de Salud Carlos III (Spain). PARP-1 has been linked to the progression of several types of cancer. We have recently reported that PARP-1 influences tumor progression in CRC through the regulation of CSCs in a p53-dependent manner. In this study, we propose that nitric oxide (NO) produced by inducible nitric oxide synthase (iNOS) could act as a mediator. We evaluated the expression of iNOS in a cohort of patients previously used to analyze the effects of PARP-1 on CRC in relation to p53 status. We also developed an in vitro model in which PARP-1 was stably overexpressed. In CRC patients, iNOS expression correlated with the differentiation grade, and with a high expression of CSC markers, although only in wild-type p53 tumors, as previously found for PARP-1. In vitro, overexpression of PARP-1 induced increased growth and stemness in wild-type p53 cells, while exerting the opposite effect on mutated ones, as expected. Treatment with 1400 W, a selective inhibitor of iNOS, or gene silencing of the gene counteracted the effects of PARP-1 in both p53 wild-type and p53 mutated cells. Given that the development of resistance has been demonstrated after treatment with PARP-1 inhibitors, iNOS could be considered a new therapeutic target in CRC, although only in patients with wild-type p53 tumors. 2026-02-23T11:59:10Z 2026-02-23T11:59:10Z 2025-01-14 journal article del Moral-Martinez, M.; Sánchez-Uceta, P.; Clemente-Gonzalez, R.; Moreno-SanJuan, S.; PuentesPardo, J.D.; Khaldy, H.; Lopez-Perez, D.; Arnedo, J.; Casado, J.; MartínezHeredia, L.; et al. iNOS-Produced Nitric Oxide from Cancer Cells as an Intermediate of Stemness Regulation by PARP-1 in Colorectal Cancer. Biomolecules 2025, 15, 125. https://doi.org/10.3390/ biom15010125 2218-273X https://hdl.handle.net/10481/111391 10.3390/biom15010125 eng open access MDPI