High-throughput drug screening using a library of antibiotics targeting cancer cell lines that are resistant and sensitive to gemcitabine.

Gemcitabine is a nucleoside analog widely used as an anticancer agent against several types of cancer. Although gemcitabine sometimes shows excellent effectiveness, cancer cells are often poorly responsive to or resistant to the drug. Recently, specific strains or dysbiosis of the human microbiome were correlated with drug reactivity and resistance acquisition. Therefore, we aimed to identify antibiotic compounds that can modulate the microbiome to enhance the responsiveness to gemcitabine. To achieve this, we confirmed the gemcitabine responsiveness based on public data and conducted drug screening on a set of 250 antibiotics compounds. Subsequently, we performed experiments to investigate whether the selected compounds could enhance the responsiveness to gemcitabine. First, we grouped a total of seven tumor cell lines into resistant and sensitive group based on the IC50 value (1 μM) of gemcitabine obtained from the public data. Second, we performed high-throughput screening with compound treatments, identifying seven compounds from the resistant group and five from the sensitive group based on dose dependency. Finally, the combination of the selected compound, puromycin dihydrochloride, with gemcitabine in gemcitabine-resistant cell lines resulted in extensive cell death and a significant increase in cytotoxic efficacy. Additionally, mRNA levels associated with cell viability and stemness were reduced. Through this study, we screened antibiotics to further improve the efficacy of existing anticancer drugs and overcome resistance. By combining existing anticancer agents and antibiotic substances, we hope to establish various drug combination therapies and ultimately improve cancer treatment efficacy.