Current cancer chemotherapies are invasive, show multiple side effects and often patients became refractory to treatment. Therefore, the continuous search for new anti-tumor agents remains crucial. Quinoxalines have been reported as new anti-neoplastic agents against a variety of human cancer cell lines, with some of these molecules under clinical trial. They are heterocyclic compounds with simple synthesis methods rarely found in nature but presenting multiple biological activities. In this work we investigate the effects of the new synthetic low-weight quinoxaline PJOV56 on colon cancer cells (HCT-116).
A 48h treatment of HCT116 cells with 1.5 and 3μM of PJOV56 resulted in a significative decrease in cell growth, although this phenotype was partially reverted after treatment discontinuation. The proliferation of quinoxaline-treated cells at 6 μM was completely inhibited even upon compound withdrawal. PJOV56 also promoted changes in cell cycle, increasing subpopulation in the S and G0/G1 phases at concentrations of 3.0 and 6.0 μM, respectively. Morphological analysis revealed that the treatment caused augmented cell volume and extensive cytoplasmic vacuolization, both characteristics of autophagic phenotypes, that remained after quinoxaline removal from the cell culture. Other known autophagy markers, like Acridine Orange-stained vesicles and increased expression SA-β-galactosidase were also observed before and after quinoxaline withdrawal. Western blot analysis indicated a slight increase in Beclin-1 and a gradual elevation in LC3-II expression levels in PJOV56-treated cells in a dose-dependent manner.
We demonstrated that PJOV56 has an antiproliferative effect at the treatment conditions tested on HCT-116 cells through an autophagy-dependent mechanism. Autophagy may act as a clearance mechanism of cancer arrested cells. These results suggest PJOV56 as a new anticancer prototype compound.