Study of the biological effects of pectins extracted from different types of fruits in the treatment of cancer cells of the intestinal epithelium

Author(s)

Raissa Sansoni do Nascimento

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2020-07-07

Examining board members

João Paulo Fabi; Thomas Prates Ong; Marco Aurélio Silva Tiné

• Advisor: João Paulo Fabi

Abstract

Pectins are soluble dietary fibers that can show anti-tumor activity when they bind to the pro-metastatic protein galectin-3 (GAL-3) produced by cancer cells. This binding and the consequent inhibition of GAL-3 reduces the ability of cancer cells to communicate biochemically, leading to a decrease in cell proliferation. The purpose of this project was to establish the relationship between the chemical composition of unmodified and chemically modified chayote, papaya and passion fruit pectins with possible beneficial effects on the cultivation of colon epithelial cancer cells. During the execution of the project, experiments have been carried out to extract, purify and chemically characterize unmodified and modified water-soluble non-starch polysaccharides fractions of chayote, papaya and passion fruit. These fractions were tested for purity (presence of proteins and phenolic compounds) and for affinity with recombinant human GAL-3, in addition to tests on colorectal cancer cell cultures, evaluating the action of treatments on cell viability, in the cell cycle, apoptosis and gene expression. The study of the possible interaction of GAL-3 with certain ligands has been carried out through the hemagglutination test using commercially available rabbit red blood cells; the biological response in vitro in relation to the treatment of epithelial colon cancer cells has been carried out through the analysis of cell viability by the MTT assay. Flow cytometry showed that the modified pectins caused the cell cycle arrest in G1 and induced late apoptosis. The expression of genes related to apoptosis, regulation, migration, differentiation and cell proliferation was measured by qPCR and the results were different, depending on the type of pectic fraction and the cell line analyzed. The polysaccharide fractions that were chemically modified showed reduced average molecular size, resulting in a greater release of galacturonans and a greater inhibitory potential for GAL-3. It was also observed a lower maintenance of cell viability in colorectal epithelial tumor cells (cell lines HCT-116 and HT-29), in addition to the cytostatic effect of treatments on the cell cycle and induction of late apoptosis. These positive biological effects may be a consequence of the decrease in molecular weight and the presence of galactans, showing that chemical modification of non-starch polysaccharides from fruits can increase the biological activity in vitro in colon cancer cell cultures. (AU)

• FAPESP's process: 16/10895-3 - The biological effects of modified pectins extracted from different fruits on colon cancer cells
• Grantee: Raissa Sansoni Do Nascimento
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)