The effect of high dose vitamin A on the morphology and proliferative activity of xenograft lung and head and neck cancer.

In vitro studies have suggested that vitamin A lowers invasive potential of squamous cell carcinoma. Epidemiological data have also indicated that high dose vitamin A may improve survival in patients with previously resected lung carcinoma. To our knowledge, no studies have attempted to test the in vivo effect of vitamin A on the morphology and growth rate of lung and head and neck cancer. Freshly resected tumor cell suspensions were obtained by ex vivo fine needle aspiration and injected subcutaneously in duplicate in athymic male nude mice. Two to six weeks post-engraftment tests and controls were separated for each xenograft. Mice with test xenografts were given water soluble vitamin A (Aquasol ATM, Astra pharmaceutical, Westborough, MA, U.S.A) at a dose of 10,000 U/Kg/day intraperitoneally for 6 to 10 weeks (median 8 weeks). One to two hours prior to sacrifice bromodexouridine (BrdU) was injected intraperitoneally to assess the S-phase fraction in both test and control xenografts. Blood vitamin A levels in test and control animals were measured after sacrifice using high performance liquid chromatography (HPLC). Sections of test and control xenografts were routinely stained to assess morphologic differentiation and mitotic counts. Unstained sections of xenografts were immunostained by the antibody to BrdU to test for BrdU labeling index (BLI) reflecting S-phase fraction (SPF) and also by the MIB-1 antibody to assess proliferative activity. Eighteen tumors were studied. These included 9 squamous cell carcinomas of the lung, 5 squamous cell carcinomas of the head and neck, and 4 adenocarcinomas of the lung. Blood levels of vitamin A in test animals were 7 to 23 times those of the control animals (median 13 times). Neovascularization of the xenografts was seen in all cases. The morphology and mitotic activity of the test and control xenografts showed no significant difference. SPF and proliferative activity measured by BrdU and MIB-1 immunolabelling respectively showed no significant difference between test and control xenografts. Our study suggests that there is no significant in vivo effect of high dose vitamin A on the morphology and growth rate of xenografted non small cell carcinoma of the lung or squamous cell carcinoma of the head and neck.