Rejection of cytotoxic T lymphocyte-resistant Meth A tumor cells by immunotherapy

Abstract

One implication of the varied responses of tumor cells to chemotherapy and other treatment modalities is that the successful eradication of disseminated tumor cells will have to be highly selective and circumvent the problems of biologic heterogeneity of neoplasms. In the past, it has been assumed that cytotoxic T lymphocyte (CTL) is the major effector cells responsible for the rejection. In the present study, we examined the growth of CTL-resistant Meth A tumor cells transplanted intraperitoneally (i.p.) or intradermally (i.d.) into a syngeneic strain (BALB/c) of mice. Intraperitoneally injected Meth A tumor cells continued to grow in BALB/c mice, and the mice died around 2 weeks after injection, as expected. Unexpectedly, however, i.d. injected Meth A tumor cells grew transiently in the same strain of mice with a peak on days 8-12, and were rejected around 3 weeks after injection. When we i.p. injected Meth A tumor cells into i.d. immunized mice, the i.p. injected tumor cells were rejected after a several-days growth of tumor. The peritoneal exudate cells harvested on day 6 exhibited a high cytotoxic activity against Meth A tumor cells. These results suggest that the effector cells responsible for the rejection of i.d. injected tumor cells from BALB/c mice or for the rejection of i.p. injected ones from the i.d. immunized mice may be non-T cells and that the effector mechanism can be memorized. [J Physiol Sci. 2006;56 Suppl:S240]