Biology subjects

Buckhaults, P. J.

Publications and source records attributed to Buckhaults, P. J..

4 recordsLinked to original sources

bioRxiv2025

Overcoming Cisplatin Resistance in TP53-null Colon Cancer Organoids

Cisplatin chemotherapy of colorectal cancer (CRC) is associated with dose-limiting side effects and the development of drug resistance, resulting in reduced therapeutic effectiveness. The resistant phenotype in colon cancer is primarily due to changes in p53-regulated DNA damage signaling and /or defects in the cellular mismatch-repair pathway. Therefore, enhancing the efficacy of cisplatin chemotherapy remains a significant challenge. In this study, we used a TP53-KO patient-derived colon tumor organoid model to perform a genome-wide CRISPR KO screen in the absence and presence of cisplatin and identified gene knockouts that re-sensitize cisplatin-resistant TP53-KO colon cancer organoids to cisplatin treatment. Knockout of genes in the DNA Repair pathways, including Fanconi Anemia (FA cause re-sensitization of TP53-KO colon cancer cells to cisplatin. Inhibition of genes ERCC6, FANCL, and BRIP1 enhances cisplatin-induced cell death in TP53-KO colon cancer organoids. These findings suggest that targeting these pathways could be an effective approach to overcome chemoresistance of TP53-muatnt colon cancer cells to cisplatin.

molecular biology↗

bioRxiv2025

StarTrace: A Multiplex Organoid Avatar Drug Testing Platform for Personalized Medicine

The goal of precision medicine is to improve clinical outcomes of cancer patients by choosing treatments most likely to work. One idea is to match tumor response to cancer-causing somatic mutations, but this strategy still faces limitations in colorectal cancer due to poorly understood genetic influences on drug resistance. We describe here a simple direct drug sensitivity assay platform applied to mixtures of patient-derived organoid avatars as a practical solution for choosing therapy, sidestepping the need for exhaustive knowledge of drug-genetic interactions. This approach rank orders individual patient organoid avatars responses to various drugs to be used to guide treatment choices. The platform multiplexes organoids using a clonal barcoding method, called StarTrace, which simultaneously tests pools of multiple patients organoid avatars for sensitivity or resistance to small molecule inhibitors. We utilized both quantitative real-time PCR-based and single-molecule sequencing assays to track the relative Darwinian fitness of each barcoded organoid within the pool. StarTrace offers a rapid, cost effective and sensitive testing platform that could be useful for either preclinical drug development or tailoring personalized therapy.

molecular biology↗

bioRxiv2022

TP53 knockout in MCF7 breast cancer cells induces sensitivity to fluoropyrimidine drugs.

TP53 mutations are present in all molecular subtypes of breast cancer and often correlate with decreased survival; however, few therapeutic options exist for patients with TP53-mutant breast cancers. To discover therapeutic strategies for these patients, we investigated the sensitivity of 129 FDA-approved chemotherapies to TP53-KO and TP53-WT MCF7 breast adenocarcinoma cells and found p53 loss to confer sensitivity to 5-fluorouracil (5-FU). We then treated the p53-null cells and isogenic controls with F10, a second-generation polymeric fluoropyrimidine, and found this preferential cytotoxicity of TP53-KO cells to be significantly magnified. F10 killing could only minimally be rescued by addition of exogenous uridine, whereas it was completely abrogated by addition of exogenous thymidine, suggesting DNA incorporation to be central to the cytotoxic mechanism of action. Furthermore, F10 killing of p53-null cells was persistent even in heterogeneous cellular mixtures more reflective of natural tumor evolution. Together, our results suggest F10 may widen the therapeutic window for TP53-mutant breast cancer by enhancing genotoxicity in cells resistant to apoptosis.

cancer biology↗

bioRxiv2020

Store Independent Ca2+ Entry Regulates the DNA Damage Response in Breast Cancer Cells

Although the mainstay of treatment for hormone responsive breast tumors is targeted endocrine therapy, many patients develop de novo or acquired resistance and are treated with chemotherapeutic drugs. The vast majority (80%) of estrogen receptor positive tumors also express wild type p53 protein that is a major determinant of the DNA damage response. Tumors that are ER+ and p53WT respond poorly to chemotherapy, although the underlying mechanisms are not completely understood. We describe a novel link between store independent Ca2+ entry (SICE) and resistance to DNA damaging drugs, mediated by the secretory pathway Ca2+-ATPase, SPCA2. In luminal ER+/PR+ breast cancer subtypes, SPCA2 levels are high and correlate with poor survival prognosis. Independent of ion pump activity, SPCA2 elevates baseline Ca2+ levels through SICE and drives cell proliferation. Attenuation of SPCA2 or depletion of extracellular Ca2+ increased mitochondrial ROS production, DNA damage and activation of the ATM/ATR-p53 axis leading to G0/G1 phase cell cycle arrest and apoptosis. Consistent with these findings, SPCA2 knockdown confers chemosensitivity to DNA damaging agents including doxorubicin, cisplatin and ionizing radiation. We conclude that elevated SPCA2 expression in ER+ p53WT breast tumors drives pro-survival and chemotherapy resistance by suppressing the DNA damage response. Drugs that target storeindependent Ca2+ entry pathways may have therapeutic potential in treating receptor positive breast cancer.

cancer biology↗