Morphological and immunological observations on the effects of hexadecylphosphocholine (HPC) in nude mice bearing MT-1 breast cancer xenografts.

Hexadecylphosphocholine (HPC) is active against experimental and clinical breast cancer in vivo but the precise mechanisms involved are not fully understood. Studies in this and other laboratories have demonstrated that HPC has very significant activity against MT-1 human mammary xenografts in nude mice and preliminary studies have indicated immunomodulatory effects. The aims of this study were to investigate the influence of HPC on immune cell populations in nude mice bearing MT-1 xenografts and the effects of HPC on MT-1 xenograft vascularisation. After treatment, significant increases in the number of cells were observed in the spleen paracortex and cortex and the follicles were more developed compared with lymph nodes from untreated mice. Immune cell populations in spleens from untreated MT-1 tumour bearing nude mice were compared with those from HPC treated mice. After HPC treatment, increases in the macrophage and T cell populations as well as T cell subsets were observed in spleens. Histological examination of treated tumours showed the presence of giant cells and large lytic areas. Immunostaining revealed increases in endothelial cells (p < 0.005) associated with massive infiltration of M phi, T cells and B cells. The results suggest that HPC affects the development of immune cells in the secondary immune tissues of nude mice. An increase in tumour vasculature appears to be accompanied by infiltration of immune cells into the tumour.