Background: rTBL-1, a recombinant lectin from
Phaseolus acutifolius, exhibit proapoptotic activity on colon cancer cells and inhibitory properties on colon tumorigenesis in vivo. Apoptosis has been associated with a phospho-EGFR/phospho-p38/phospho-p53 mechanistic axis. Immunogenicity data have been observed in treated animals, but
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Background: rTBL-1, a recombinant lectin from
Phaseolus acutifolius, exhibit proapoptotic activity on colon cancer cells and inhibitory properties on colon tumorigenesis in vivo. Apoptosis has been associated with a phospho-EGFR/phospho-p38/phospho-p53 mechanistic axis. Immunogenicity data have been observed in treated animals, but its possible involvement in the antitumor response remained unexplored.
Objective: We investigated whether the cytotoxic activity of
rTBL-1 depends on EGFR and its capacity to produce antitumor responses on syngeneic colon cancer in mice, with and without T cells, in order to explore its possible involvement in the process.
Results: rTBL-1 exhibited cytotoxic effects in a concentration-dependent manner in both EGFR
+ (MC-38) and EGFR
− (CT-26) colon cancer cells with LC
50 values of 23.50 and 30.01 µg/mL, respectively (
p =
0.063). Apoptotic effects were slower and longer-lasting in MC-38 than in CT-26 cells. Significant increases in caspase-3 proteolytic activation and PARP1 cleavage were detected in both cell types, despite PARP1 rheostasis in CT-26 cells. Intralesional treatment with
rTBL-1 inhibited the growth of established tumors in immunocompetent BALB/c mice in 27.81% (
p =
0.0008) with a benefit in survival (
p =
0.022), but not in immunodeficient BALB/c nude mice.
Conclusions: rTBL-1 induces apoptosis in colon cancer cells by EGFR independent mechanisms, although its presence could be related to deeper responses. Unresponsiveness in nude mice indicated that
rTBL-1 antitumor effect is the synergistic result of apoptosis induction and T cell-mediated cytotoxicity in the tumor. Future studies will focus on the immunogenic effects triggered by the antitumor activity of
rTBL-1 in colon cancer.
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