Cancer stem-like cells (CSCs) and tumor-initiating cells (
TICs) are a small population of
cancer cells that share three properties:
tumor initiating ability, self-renewal, and differentiation. These properties suggest that CSCs/
TICs are essential for
tumor maintenance, recurrence, and distant
metastasis. Here, we show that cytotoxic T lymphocytes (CTLs) specific for the
tumor-associated
antigen CEP55 can efficiently recognize colon CSCs/
TICs both in vitro and in vivo. Using
Hoechst 33342 dye staining, we isolated CSCs/
TICs as side population (SP) cells from
colon cancer cell lines SW480, HT29, and HCT15. The SP cells expressed high levels of the stem cell markers SOX2, POU5F1, LGR5, and ALDH1A1 and showed resistance to chemotherapeutic agents such as
irinotecan or
etoposide.To evaluate the susceptibility of SP cells to CTLs, we used CTL clone 41, which is specific for the CEP55-derived antigenic
peptide Cep55/c10orf3_193 (10) (VYVKGLLAKI). The SP cells expressed HLA class I and CEP55 at the same level as the main population cells. The SP cells were susceptible to CTL clone 41 at the same level as main population cells. Furthermore, adoptive transfer of CTL clone 41 inhibited
tumor growth of SW480 SP cells in vivo. These observations suggest that Cep55/c10orf3_193(10)
peptide-based
cancer vaccine therapy or adoptive cell transfer of the CTL clone is a possible approach for targeting
chemotherapy-resistant colon CSCs/
TICs.