Therapeutic efficacy of cancer stem cell-based vaccine in colorectal murine model: reduced tumor growth and prolonged survival

Various forms of cancer immunotherapy are promising in overcoming the obstacles posed by resistance to conventional chemo- and radiotherapy. Cancer vaccines could serve as beneficial adjuncts to conventional therapies, offering the potential for fine-tuning to reduce relapse and related mortality. Continuing prior investigations, a therapeutic colorectal cancer stem cell (CSC)-based vaccine was developed to explore whether this vaccination could inhibit the formation and prolong survival rates in a mouse model of colorectal cancer. CSCs were enriched from the CT-26 cell line using sphere formation assay and characterized by real-time q-PCR for stemness genes (Oct4, Sox2, and Nanog) and tumorigenesis assay in syngeneic BALB/c mice. Different groups of mice were intraperitoneally immunized with the CSC lysate-based vaccine, the parental cell lysate-based vaccine, and control groups following subcutaneous challenge with CT-26 cells. Beyond analyzing tumor growth and survival rates, histological analysis of tumor tissues was conducted using comprehensive hematoxylin and eosin (H&E) staining, and antibody responses in vaccinated mice were evaluated by flow cytometry and immunofluorescence. Immunization of tumor-bearing mice with the CT-26 CSC lysate-based vaccine caused delayed tumor formation, reduced tumor growth rate, and enhanced survival rate compared to the control groups. The histological responses observed in the lysate vaccination subgroups indicated a potent immune response. Furthermore, flow cytometry and immunofluorescence analyses demonstrated the production of anti-CSC and anti-parental cell antibodies in mice immunized with CT-26 CSC and parental cell lysates. These findings suggest that targeting CSCs using a CSC lysate-based vaccine can stimulate cellular and humoral immunity and represent a novel therapeutic approach to complement conventional antitumor therapies.