Abstract 299P
Background
Triple-negative breast cancer (TNBC) accounts for 10-20% of all breast cancer (BC) cases. The high rate of aggressiveness, relapse and mortality require the search for new therapeutic targets. ACSL4 (Acyl-CoA Long Chain Family Member 4), a key enzyme in the fatty acids’ metabolism, has been related to modulation of drug resistance. The hypothesis of this work is that microRNAs-449 family (miRs-449) directly regulates ACSL4, and therefore, could modulate the response to doxorubicin (DOX).
Methods
The expression of miRs-449 and ACSL4 mRNA among BC subtypes was analyzed in GEO (Gene Expression Omnibus) databases. ACSL4 mRNA and miRs-449 expression was evaluated in a cohort of TN primary BC patients (n=36) and compared with healthy breast tissues (n=23) from Hospital Clínico de Valencia. Prognostic value of ACSL4 and miRs-449 was obtained by Kaplan-Meier Plotter software. TNBC cell lines, including a DOX-resistant clone (XC1), were used for in vitro validation. Luciferase assay was performed to asses miRs-449/ACSL4 direct interaction. Gene gain/loss of function by miRs-449 mimics/inhibitors and ACSL4 siRNA was performed. Gene and protein modulation of ACSL4 and its downstream pathways were analyzed by qRT-PCR, WB and functional assays.
Results
The expression of ACSL4 is higher in breast cancer than healthy tissues being more significant in TNBC. In addition, ACSL4 overexpression is observed in XC1 and patients who relapse after doxorubicin-containing chemotherapy treatment (p<0.01). Moreover, ACSL4 overexpression is correlated with lower DFS (p<0.05). Inversely, miRs-449 are downregulated in parental TNBC cell line and patients, and its high expression is associated with better OS (p<0.05). Luciferase assay shows that ACSL4 is a direct target of miR-449a and b. Both, ACSL4 silencing and miRs-449 gain of function, inhibit cell proliferation, colony formation, migration, invasion and sensitizes XC1 to DOX through mTOR inactivation and ABCG2 downregulation.
Conclusions
This study suggests a possible role of miRs-449 family in DOX response through direct ACSL4 repression and mTOR/ABCG2 axis modulation in TNBC.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
Biomedical Research Institute INCLIVA; Centro de Investigación Biomédica en Red de Cáncer (CIBERONC).
Funding
Biomedical Research Institute INCLIVA Centro de Investigación Biomédica en Red de Cáncer (CIBERONC).
Disclosure
All authors have declared no conflicts of interest.