Background: Aberrant lipid metabolism is associated with poor prognosis in colorectal cancer (CRC). Fatty acid synthase (FASN), a key enzyme of lipogenesis, is overexpressed and a therapeutic target in CRC. Overexpression of CD36, a fatty acid translocase, plays a pro-tumorigenic role in CRC. BRAFV600E is the mutation occurring in about 10-15% of CRC cases. BRAF-targeted therapy is effective, but quickly developed resistance is an issue. Our preliminary data show that development of resistance to BRAF-targeted therapy is associated with an increase in expression of FASN, CD36, accumulation of triglycerides (TGs), and mitochondrial respiration. Therefore, our central hypothesis is that inhibition of lipid metabolism will sensitize CRC cells to BRAF inhibitors and overcome acquired resistance. Methods: We established HT29 cells and primary PT130 and PT2449pt cells resistant to PLX8394, a novel BRAF inhibitor. IC50 curves, PrestoBlue viability, CytoSelect™ 24-Well Cell Invasion, and Triglyceride Assays, Seahorse XF analysis, western blot, and confocal microscopy were used to evaluate differences between parental and resistant cells. RNA-seq and lipid analysis were used to evaluate changes in gene expression and lipids levels. Combination of PLX8394 and TVB3664 (FASN inhibitor) was tested on cell viability in parental and resistant cells. Results: PLX8394 resistant cells have a higher IC50, an increased proliferation, and invasion compared to parental cells. An increase in invasion of resistant cells is associated with a decrease in E-cadherin. RNA sequencing shows a significant increase in FASN expression. Western blot on resistant cells confirms upregulation of FASN, CD36, and other lipogenic markers. Consistently, resistant cells have an increase in levels of triglycerides as compared to parental cells. Seahorse XF Cell Mito Stress Test shows that resistant cells forgo the Warburg effect and instead rely more heavily on oxidative phosphorylation. To further support our hypothesis, FASN shRNA knockdown of FASN in parental HT29 cells is more susceptible to PLX8394 treatment compared to control. We also observed the synergetic effect of PLX8394 and TVB3664 treatment on cell viability in parental cells, but not in resistant cells. Conclusion: Our study demonstrates that resistance to BRAF inhibitors is associated with a significant increase in proliferation, metastasis, and upregulation of lipid metabolism. We show that combination of FASN and BRAF inhibitors has a combinational effect on inhibiting cell viability in parental but not resistant cells, suggesting that the addition of FASN inhibitor to the standard regimen for BRAFV600E mutation positive patients can improve efficacy of these therapies. Additional screening of lipid metabolism-targeted therapies in combination with standard BRAF regimens are needed to develop novel and more efficacious strategies for CRC patients with BRAF mutations. Citation Format: Mariah E. Geisen, Dang he, Chi Wang, Jill M. Kolesar, Yekaterina Zaytseva. Targeting lipid metabolism to improve efficacy of braf-targeted therapy in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 414.
Prostate cancer (PCa) is the most diagnosed worldwide. PCa development and progression require androgen receptor (AR) signaling, which stimulates its downstream gene expressions and cancer progression. While second-generation anti-androgen drugs plus androgen deprivation therapy (ADT) remains the first-line treatment for advanced prostate cancer patients, around one-third of patients will relapse in a short period. Advanced prostate cancer results in more mortalities than primary PCa patients. Evidence shows that the recurrence is caused by AR overexpression, AR variants, AR mutations, and signaling crosstalk. Thus, it is urgently needed to discover a novel therapeutic strategy for treating advanced prostate cancer. The heat shock protein family (HSP), including HSP90 and HSP70, play important roles in refolding aggregated protein for cancer cell proteomic equilibrium. HSP is induced primarily by heat shock factor (HSF1). As AR’s chaperone protein, HSP70 and HSP90 increase AR transcription activity. Inhibiting HSP70 and HSP90 promotes STUB1, an E3 ligase, binding to AR and AR - V7, and ubiquitination. Artesunate (ART) is a semi-synthetic ingredient from Artemisia annua and is the most common treatment for malaria throughout the world. It was approved for medical use by the FDA (Food and Drug Administration) (Food and Drug Administration). Recently ART has been unveiled for its anticancer properties. However, the efficacy of ART treatment in advanced prostate cancer and the direct target of ART have not been investigated yet. Herein, we have examined the efficacy of combining Enzalutamide (Enza) and ART in advanced prostate cancer cell lines. We also performed unbiased bioinformatics analysis using RNA seq results in enzalutamide-resistant cell line C4-2R cells and 22RV1 cells to investigate the cell response toward ART treatment. We identified ART could downregulate of AR signaling pathway. Moreover, we determined that ART treatment induces AR degradation in proteasome dependent manner. Interestingly, we found HSP70 and HSP90 are also decreased in RNA seq results. Taking these together suggests that ART may target HSF1 directly. Our results suggest ART induced AR degradation could be a promising clinical strategy for advanced prostate cancer. Citation Format: Xinyi Wang, Fengyi Mao, Jinghui Liu, Yifan Kong, Dang he, Chi Wang, Zhiguo Li, Xiaoqi Liu. Artesunate increases enzalutamide efficacy in advanced prostate cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5508.
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