INVESTIGATING THE COMBINED EFFECTS OF JADOMYCIN B AND CELECOXIB AGAINST TRIPLE-NEGATIVE BREAST CANCER XENOGRAFTS IN ZEBRAFISH LARVAE

Abstract

Breast cancer affects 1 in 8 Canadian women over their lifetime, with triple-negative breast cancer (TNBC) making up 10-20% of all advanced stage breast cancers. TNBCs lack receptors making treatment with hormone targeted therapies much more difficult, requiring cytotoxic chemotherapies. However, prolonged chemotherapy exposure can lead to multi-drug resistance (MDR), resulting in treatment failure. Jadomycin B, a natural product of Streptomyces venezuelae, has shown cytotoxic effects towards MDR TNBCs. This effect has shown to be enhanced when combined with selective COX-2 inhibitor, celecoxib, towards TNBC cells in vitro, suggesting jadomycin B’s possible interaction within the COX-2 signaling pathway. With promising in vitro data, it is important to transition to in vivo models for drug development. Zebrafish larval xenografts provide a reliable platform for cancer modeling and drug screening. This study aimed to develop a human TNBC zebrafish xenograft model to examine the effects of jadomycin B in combination with celecoxib in vivo. Using zebrafish larvae as a platform for drug toxicity, a maximum tolerated dose (MTD) was determined to be 20 uM for jadomycin B and 5 uM for celecoxib when administered alone or in combination. Stable fluorescent human TNBC MDA-MB-231 cell lines (231-EGFP, 231-mCherry) were generated using CRISPR/Cas9 technology and characterized through PCR, DNA sequencing, and MTT assays. Zebrafish embryos were then xenotransplanted with 231-EGFP cells and treated with the maximum tolerated doses (MTD) of jadomycin B and celecoxib alone or in combination. The combination of 20 uM of jadomycin B and 5 uM of celecoxib resulted in a 75% reduction in 231-EGFP cell fluorescence intensity, that was significantly greater compared to a 39% and 15% reduction for 20 uM of jadomycin B and 5 uM of celecoxib alone, respectively (p <0.05). This work successfully developed a zebrafish larval xenograft model of human EGFP-expressing TNBC. Using this model, it was demonstrated that the combination of jadomycin B and celecoxib showed favourable safety profiles and enhanced the anticancer effects of jadomycin B, similar to the effects previously determined in vitro.