Adoptive immunotherapy using lymphokine-activated killer cells and recombinant interleukin-2 in preventing and treating spontaneous pulmonary metastases of syngeneic Dunning rat prostate tumor

Therapeutic effect of lymphokine-activated killer cells treated with low-dose ionizing radiation on osteosarcoma

The aim of the present study was to investigate the effect of lymphokine-activated killer (LAK) cells, which received low-dose ionizing radiation, on the treatment of osteosarcoma in rats. The cultured UMR-106 cells were inoculated under the anterior chest skin of 24 rats to establish an osteosarcoma model. In addition, the LAK cells from 24 mice were exposed to doses of 0 (control group), 0.65 or 3.25 mGy X-ray radiation. The tritiated thymidine (³H-TdR) release method and Winn assay were performed to determine the antitumor effects of the LAK cells. The proliferation of the mouse LAK cells treated with 3.25 mGy radiation was significantly higher than that for those treated with 0 or 0.65 mGy radiation, which suggested that low-dose ionizing radiation stimulates the proliferation of LAK cells. The tumor-bearing rats were divided into three groups and injected with LAK cells that had already received 0, 0.65 or 3.25 mGy radiation. The mean survival time of the 3.25-mGy group was longer than that of the 0- and 0.65-mGy groups. After 30 days, tumors with weights of ~6.25 and 2.0 g were identified in the rats of the 0- and 0.65-mGy groups, respectively. However, tumor proliferation was not detectable in the rats of the 3.25-mGy radiation group. Therefore, low-dose ionizing radiation effectively kills osteosarcoma cells in rats by stimulating the proliferation and enhancing the cytotoxicity of LAK cells.

Exogenous antigen targeted to FcgammaRI on myeloid cells is presented in association with MHC class I

Vaccine therapy is attractive for prostate cancer patients because the tumor is slow growing (allowing time to augment host responses) and occurs in an older population less likely to tolerate more toxic treatments. We have constructed an expression vector based on a monoclonal antibody (mAb) that targets the high affinity receptor for IgG (FcgammaRI, CD64) which is exclusively expressed on myeloid cells including dendritic cells (DC). The heavy chain of mAb H22 CH2 and CH3 domains were removed and replaced with the gene for prostate specific antigen (PSA). Using that vector, we have constructed and purified FPH22.PSA, a fusion protein that targets PSA to FcgammaRI on antigen presenting cells (APC). This fusion protein has an apparent molecular mass of 80-83 kDa, binds to FcgammaRI with high affinity and expresses PSA. We demonstrate that FPH22.PSA targeted PSA was internalized and processed by the human myeloid THP-1 cell line resulting in presentation of MHC class I-associated PSA peptides and lysis of THP-1 by PSA-specific human CTL. Moreover, pretreatment of THP-1 cells with antibodies to block either FcgammaRI or MHC class I, blocked lysis indicating that targeting to FcgammaRI results in presentation of exogenous antigen on MHC class I molecules. These data demonstrate that FPH22.PSA was processed in such a manner by the myeloid cell line to allow for presentation of immunodominant peptides in MHC class I molecules and suggests that uptake of antigen via FcgammaRI results in cross-priming.

Progress in active specific immunotherapy of prostate cancer

Treatments available for metastatic prostate cancer have failed to demonstrate significant curative potential. Current efforts are now directed towards developments of novel strategies for the treatment of metastatic prostate cancer. Cancer immunotherapeutic strategies utilize patient immune system components to kill cancer cells. This review discusses progress in active specific immunotherapeutic approaches as potential alternative methods in the treatment of metastatic prostate cancer. Various methods of augmenting the immune response against prostate cancer are discussed including systemic cytokine adjuvant therapy, cytokine gene transduced tumor vaccines, non-antigen specific immunization, DNA and peptide vaccines plus adjuvants, as well as dendritic cell-based cancer vaccines.

The effects of growth factors associated with osteoblasts on prostate carcinoma proliferation and chemotaxis: implications for the development of metastatic disease

The extensive mortality and morbidity associated with prostate cancer is caused by the high prevalence of metastatic disease at the time of diagnosis. The area most frequently involved in metastatic prostate cancer is the skeleton. Unlike other cancers, which metastasize to bone and destroy the bone matrix, prostate cancer is unique in that it is osteogenic, resulting in the formation of dense, sclerotic bone with high levels of osteoblastic activity. We proposed that factors produced by bone cells may be responsible for the development of prostate carcinoma metastasis. We studied the effects of these growth factors on prostate cell proliferation by [3H]thymidine incorporation and chemotaxis by the double-filter chamber method. Three prostate carcinoma cell lines were studied, LNCaP (androgen responsive) and PC-3 and DU-145 (androgen unresponsive). The bone-associated growth factors tested were: insulin-like growth factors I and II (IGF-I, IGF-II), transforming growth factor beta, interleukin (IL)-1 beta, IL-6, and tumor necrosis factor alpha (TNF-alpha), IGF-I and IGF-II significantly increased proliferation in all three cell lines, whereas IL-6, TNF-alpha, and IL-1 beta significantly decreased proliferation. Transforming growth factor beta induced a biphasic response in proliferation in DU-145 and PC-3 cells and produced no response on LNCaP cells. Increased cell chemotaxis occurred in the presence of IGF-I and IGF-II, and decreased cell chemotaxis occurred with the addition of TNF-alpha and IL-1 beta. These data indicate that growth factors produced by bone cells alter prostate carcinoma cell proliferation and chemotaxis and suggest that modulations of the production of these factors may be a potential therapeutic intervention in deterring the metastasis of prostate carcinoma to bone.

Possible biological mechanisms for a relationship between vasectomy and prostatic cancer

Four hypotheses have been reviewed, each of which might serve as a hypothetical biological explanation for a relationship between vasectomy and prostate cancer. The endocrine hypothesis is the only one of these with any firm data to support it, although the majority of the available data does not lend credibility to that theory. The other hypotheses are purely speculative with no hard data to support them. In conclusion, it seems highly unlikely, but not impossible, that there is a biological mechanism supporting a relationship between vasectomy and prostate cancer.