(P13-034-23) Peptides From Cowpea β-Vignin Exerted Anticancer Effect by Causing Apoptosis and Cell Cycle Arrest in Colon Cancer Cells

Objectives: To evaluate and compare the anticancer effect of β-vignin digest, VIPASY and AQQSY peptides from cowpea β-vignin protein in colon cancer cells.

Methods: Cowpea β-vignin protein was isolated and digested following the INFOGEST protocol with some modifications. In silico hydrolysis of β-vignin protein and screening of peptides interacting with palbociclib binding site on cyclin-dependent kinase 6 resulted in the selection of peptides Val-Ile-Pro-Ala-Ser-Tyr (VIPASY) and Ala-Gln-Gln-Ser-Tyr (AQQSY). Cell viability of colon cancer (HCT-116) and non-cancer (CCD-33Co) cells was assessed after 24h with oxaliplatin (OXA) (2.5 – 160 µM), β-vignin digest (VD) (12.5 – 800 µg/mL), palbociclib (PAL) and peptides (VIPASY, AQQSY) (12.5 – 400 µM). Selectivity index (SI) was calculated [IC₅₀ non-cancer cells/IC₅₀ cancer cells]. Apoptosis and cell cycle modulation was evaluated by flow cytometry in HCT-116 cells (IC₃₀, 24h).

Results: HCT-116 cell viability was affected by OXA (IC₅₀ = 160.50 ± 1.18 µM), however it was the least selective treatment for cancer cells (SI=0.15). VIPASY (IC₅₀ = 283.10 ± 1.21 µM) had a significant effect (p < 0.001) on HCT-116 cells with a higher SI (2.30) compared to PAL (IC₅₀ = 379.30 ± 1.02 µM; SI=0.44) and AQQSY (IC₅₀ = 656.30 ± 1.09 µM; SI=1.14). VD treatment (IC₅₀ = 42.30 ± 1.06 µg/mL) had the highest SI (3.33). Cell cycle arrest in G0/G1 phase was observed when HCT-116 cells were treated with PAL, OXA, VD, and AQQSY. Cells in G0/G1 phase increased from 39% for untreated cells to 88% when treated with PAL, 90% with OXA, 88% with AQQSY, 57% with VD, and 45% with VIPASY. Untreated cells had 3.5% of apoptotic cells, while treatment with OXA increased apoptotic cells to 55%, and VIPASY to 45%, followed by AQQSY, VD and PAL to 25%, 21% and 15%, respectively. Specific markers tested suggested that treatments affected the p16 and cyclin A pathways.

Conclusions: Peptides VIPASY, AQQSY and VD had anticancer effects affecting HCT-116 cell viability and were more selective than OXA and PAL. VD and AQQSY caused cell cycle arrest at G0/G1 phase and VIPASY presented a 12-fold increase in apoptotic cells compared to untreated cells. Both peptides synergistically interacted with PAL affecting HCT-116 cell viability.

Funding Sources: Funded by CAPES/Brazil - Finance Code 001, FAPESB/JCB/Brazil nº 0012/2016 and the US Department of Agriculture