Levamisole effects on major histocompatibility complex and adhesion molecule expression and on myeloid cell adhesion...

The drug levamisole has been successfully used in combination with fluorouracil to increase the disease-free interval and survival of patients who have undergone surgical resection of Dukes' stage C colon cancer. Levamisole is thought to affect the host immune response. Several recent studies have examined its effect on the expression of major histocompatibility complex (MHC) class I molecules, but the results have been inconsistent. An equally important requirement for a host cellular immune response is the adhesion of leukocytes to tumor cells. The latter may be required for cell-mediated antitumor cytotoxic responses.

We evaluated the ability of levamisole to affect the expression of MHC class I molecules and cell-adhesion molecules and determined whether levamisole could affect leukocyte adhesion to tumor cells that had been treated with the drug.

A panel of four human colon tumor cell lines (HT-29, SW-620, HCT-15, and LoVo), A-375 human melanoma cells, and human umbilical vein endothelial cells (HUVEC) were cultured in the presence of levamisole and examined by solid-phase enzyme immunoassay to determine the level of expression of MHC class I, intercellular adhesion molecule 1 (ICAM-1), vascular cell-adhesion molecule-1 (VCAM-1), leukocyte integrin VLA-4, and lymphocyte-functional antigen (LFA-1) molecules. Adhesion of HL-60 and THP-1 myeloid cells to tumor cells was also evaluated. Tumor necrosis factor (TNF) at 10 ng/mL was used as a positive control for increasing adhesion molecule expression and cell-cell adhesion. The statistical significance of differences in cell surface molecule expression and functional adhesion between treated and control cells were tested by use of analysis of variance and the two-tailed Dunnett's test.

Treatment with levamisole (0.1 and 1 micrograms/mL) caused the levels of MHC class I expression to increase approximately threefold above control levels on HCT-15 and LoVo colon tumor cells (P < .05 in each case) compared with untreated cells, caused minimal increases on HT-29 cells (to 1.5 times control levels), but caused no significant increases on SW-620 colon tumor or A-375 melanoma cells. The HCT-15 and LoVo colon tumor cells had very low basal MHC expression Levamisole (1 micrograms/mL) increased VCAM-1 expression on HT-29 and SW-620 colon tumor cells to 4.3 and 2.4 times (P < .05 in each case) control levels, respectively, doubled ICAM-1 expression on HT-29 cells (P < .05), and increased LFA-1 expression on HT-29, LoVo, and A-375 cells to 2.1, 3.2, and 1.8 (P < .05 in each case) times control levels, respectively. TNF (10 ng/mL) was used as a positive control and yielded increased expression of MHC class I molecules on the HT-29, LoVo, SW-620, and HCT-15 cells (2.5, 7.8, 1.9, and 4.8 times control levels, respectively; P < .05 in each case). TNF increased VCAM-1 expression to 4.2 times the vehicle-treated control levels (P < .05) on HT-29 cells and increased ICAM-1 expression on HT-29, LoVo, and SW-620 cells (8.4, 1.8, and 1.9 times vehicle control levels, respectively; P < .05 in each case). THP-1 and HL-60 cells demonstrated increased adhesion to levamisole-treated HT-29 colon tumor cells. HL-60 cells also exhibited increased levamisole-mediated adherence to LoVo and HCT-15 cells. Adherence by THP-1 was significantly improved after levamisole treatment of the HUVEC, SW-620, and A-375 cells (P < .05 in each case).

Levamisole can directly affect the expression and function of molecules that are engaged in cell-cell recognition and signaling on the surfaces of some tumor cell lines. However, no consistent pattern between cell-adhesion molecule expression, cell-cell adhesion, or levamisole concentration could be discerned.