Modulation of colony stimulating factor release and apoptosis in human colon cancer cells by anticancer drugs

Abstract

Modulation of the immune response against tumour cells is emerging as a valuable approach for cancer treatment. Some experimental studies have shown that secretion of colony stimulating factors by cancer cells reduces their tumorigenicity and increases their immunogenicity probably by promoting the cytolitic and antigen presenting activities of leukocytes. We have observed that human colon cancer cells (HT-29) are able to secrete granulocyte-macrophage-colony stimulating factor, granulocyte-colony stimulating factor and macrophage-colony stimulating factor when stimulated with cytokines (IL-1beta and TNF-alpha). In this study we assessed, for the first time, the effects of several anticancer drugs on colony stimulating factor release or apoptosis in HT-29 cells. Cytokine-induced release of granulocyte-macrophage-colony stimulating factor, granulocyte-colony stimulating factor and macrophage-colony stimulating factor was significantly increased by cisplatin and 6-mercaptopurine. Taxol only increased macrophage-colony stimulating factor release while reduced that of granulocyte-colony stimulating factor. No changes in colony stimulating factor secretion were observed after treatment with methotrexate. Only cisplatin and taxol induced apoptosis in these cells. Secretion of colony stimulating factors by colon cancer cells may contribute to the immune host response against them. Anticancer drugs such as cisplatin and 6-mercaptopurine increase colony stimulating factor secretion by cytokine stimulated cancer cells probably through mechanisms different to those leading to cell apoptosis, an effect that may contribute to their anti-neoplasic action.

Figure 1

Release of GM-CSF, M-CSF and G-CSF by HT-29 cells in the presence or absence of IL-1β and TNF-α (both 10 ng ml⁻¹, 24 h). Results expressed as mean±s.e.m. (n=20 per group). ***P<0.001 vs respective control value (2-tailed Student's t-test).

Figure 2

Effects of 6-MP, cisplatin and taxol on the release of G-CSF, GM-CSF or M-CSF by cytokine stimulated HT-29 cells (IL-1β and TNF-α, both 10 ng ml⁻¹, 24 h). Results expressed as mean±s.e.m (n=5 per group). *P<0.05, **P<0.01 vs value in the respective vehicle-treated cells (ANOVA+Dunnet test).

Figure 3

Effects of cycloheximide (10⁻⁶ M) on the release of GM-CSF, M-CSF or G-CSF by cytokine stimulated HT-29 cells (IL-1β and TNF-α, both 10 ng ml⁻¹, 24 h). Cycloheximide was added to the medium at the same time or 6 h before cytokines. Results expressed as mean±s.e.m. of the number of experiments shown above each column. *P<0.05 and ***P<0.001 vs value in the respective vehicle-treated cells (2-tailed Student's t-test).

Figure 4

Effects of colchicine on (A) G-CSF, GM-CSF or M-CSF release by cytokine stimulated HT-29 cells (IL-1β and TNF-α, both 10 ng ml⁻¹, 24 h) and (B) HT-29 cell apoptosis in the presence or absence of these cytokines. Results expressed as mean±s.e.m. (n=3 per group). *P<0.05, **P<0.01, ⁺P<0.05, ⁺⁺P<0.01 and ^##P<0.01 vs value in the respective vehicle-treated cells; ^•P<0.05, ^••P<0.01 ^•••P<0.001 vs control vehicle-treated cells; °P<0.05 vs cytokine+vehicle-treated cells (ANOVA + Dunnet test).

Figure 5

Effects of cisplatin, taxol, 6-MP and methotrexate on HT-29 cell apoptosis in the presence or absence of IL-1β and TNF-α (both 10 ng ml⁻¹, 24 h). Results expressed as mean±s.e.m. (n=3 per group). *P<0.05, **P<0.01 and ***P<0.001 vs control conditions, ⁺P<0.05, ⁺⁺P<0.01 and ⁺⁺⁺P<0.001 vs cytokine treated cells, ^#P<0.05, ^##P<0.01 and ^###P<0.001 vs same drug concentration in non-cytokine treated cells (ANOVA+Tukey test).