ORCID

https://orcid.org/0000-0002-3416-8931

Date of Award

2025

Document Type

Dissertation

Degree Name

Pharmaceutical Sciences (Ph.D.)

Department

Pharmaceutical Sciences

First Advisor

Zhe-Sheng Chen

Second Advisor

Sandra Reznik

Third Advisor

John Wurpel

Abstract

Colorectal cancer (CRC) remains one of the most common causes of cancer-related mortality worldwide. Vincristine is frequently used to treat CRC, although the specific pathways leading to acquired resistance are still not fully understood. In this study, we established two novel vincristine-resistant human colon cell lines (S1/V1 and S1/V4) to explore the mechanisms underlying vincristine resistance, with a particular emphasis on the overexpression of ATP-binding cassette (ABC) transporters. The S1/V1 and S1/V4 sublines were derived by continuously exposing human S1 colon cancer cells to vincristine. An MTT cytotoxicity assay revealed that S1/V1 cells exhibit about 39-fold greater resistance to vincristine than the parental S1 cells; while the S1/V4 cells exhibit about 35-fold greater resistance to vincristine than the parental S1 cells, alongside cross-resistance to other ABCB1 substrates. RT-qPCR and Western blot analysis indicated a substantial increase in ABCB1 mRNA and protein levels in S1/V1 cells, and a substantial increase in ABCC1 mRNA and protein levels in S1/V4 cells. Immunofluorescence studies demonstrated that this elevated ABCB1 and ABCC1 is localized at the cell membrane in S1/V1 and S1/V4 cells respectively, suggesting an active efflux function. Further reversal experiments showed that inhibiting the efflux function of the respective overexpressed transporters completely eradicated the resistance to vincristine S1/V1 and S1/V4 cells. In conclusion, this research provides an in vitro CRC model of vincristine resistance and identifies ABCB1 and ABCC1 overexpression as a key contributor to acquired drug resistance. The newly developed cell lines may serve as a valuable tool for investigating strategies to overcome drug resistance and enhance CRC treatment outcomes.

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