Overcoming colorectal cancer resistance to 5-fluorouracil by targeting rac1

OTTERSTEDT, KATIA; MALIZIA, FLORENCIA; ZANOTTI, LUCIA; MAMBERTO, MACARENA; CESATTI LALUCE, NAHUEL; ÁVILA, AYLEN; ANSELMINO, LUICANO; MENACHO-MÁRQUEZ, MAURICIO

Congreso; Reunión Conjunta SAIC. SAB. AAFE. AACYTAL; 2023

Colorectal cancer (CRC) is the third most commonly diagnosedtype of cancer worldwide. 5-fluorouracil (5-FU) is a chemotherapy drug used in CRC treatment; however, half of CRCs are resistant to5-FU-based therapies. Rac1 is a key member of the Rho GTPasesfamily. Rac1 modulates cell adhesion and movement, and is highlyexpressed in tumors. Increasingly studies are reporting the role ofRac1 as a potential target for tumor therapy. The aim of this workwas to evaluate the impact of Rac1 in CRC resistance to therapy.In previous work, we identified genes and pathways associated withrecurrence after 5-FU-based therapies suggesting that Rac1 inhibi-tion could be of benefit to overcome resistance. As approximately30–40% of CRCs carry a KRAS mutation, we began evaluating therelevance of RAC1 expression in KRAS wild-type/mutated CRCs.For this, we downloaded the TCGA-COAD dataset and separatedpatients according to RAC1 expression levels, determined using the“Survminer” package. In turn, we added an additional filter separat-ing patients according to KRAS gene status. We found that high ex-pression of RAC1 was associated with poor prognosis when KRASis mutated (p<0.05). We extended this evaluation for Rac1 GEFs.To continue characterizing the role of Rac1 in CRC resistance, weevaluated parameters associated to Rac1 activity like cell and nu-clear sizes and actin arrangement in 5-FU-resistant CRC cells. Con-trol and resistant cells (generated by overexposure to 5-FU) wereplated, treated with Rac1 inhibitors or vehicle, fixed and stained withphalloidin-rhodamine and DAPI to visualize actin cytoskeleton andnuclei. Measurements were performed by Image J. We noted thatRac1 inhibition was enough to overt morphological changes asso-ciated to resistance, and re-sensitize cells to 5-FU (p<0.01). All ourdata allowed us to postulate that targeting Rac1 represents a prom-ising avenue for the development of new therapies for patients withCRC resistant to 5-FU-based therapies