Immunization using male germ cells and gametes as rich sources of cancer/testis antigens for inhibition of 4T1 breast tumors' growth and metastasis in BALB/c mice.

Recently cancer/testis antigens (CTA) have gained lots of attention as targets of immune therapy. However, the therapeutic efficacy of the CTAs single-antigen vaccines is not satisfying due to tumor heterogenicity. Therefore, many studies have focused on the enhancement of their efficacy by utilizing rich sources of tumor-associated antigens for anti-cancer vaccination. In the present study, the testicular germ cells and sperm cells as well-known sources of cancer/testis antigens were investigated for anti-4T1 breast cancer vaccination in BALB/c mice. The testicular germ cells (TGCs) and sperm cells were isolated from male BALB/c mice. The definite number of cells were homogenized and mixed with Bacillus Calmette-Guerin (BCG) for vaccination of female BALB/c mice. The treatment groups underwent 3 times of immunizations with one-week intervals and one week after the last injection, all groups were injected with 4T1 cancer cells. The TGCs + BCG (259.7 ± 39 mm) and Sperm + BCG (426 ± 52 mm) groups exhibited a significant decrease in the tumors' volume in comparison with BCG (641.3 ± 102 mm) and no-treatment (788.1 ± 117 mm) groups. Therefore, the TGCs + BCG immunized mice had the smallest tumors in comparison with all groups (P < 0.05). Also, the vital organs of TGCs + BCG (lungs: 6.8 ± 2, liver: 10.1 ± 2) immunized mice exhibited lowest metastatic burden in comparison with the Sperm + BCG (lungs: 13.5 ± 3, liver: 21.1 ± 4), BCG (lungs: 24.3 ± 4, liver: 33 ± 4), and no-treatment (lungs: 26.5 ± 6, liver: 37.3 ± 3) groups. These observations were inconsistent with the tumor-bearing mice survival evaluations as the TGCs + BCG group had longer mean survival time (79.6 ± 12 days) in comparison with other groups (no-treatment: 49.8 ± 8, BCG: 50.5 ± 10, BCG + Sperm: 64.6 ± 7 days). Therefore, TGCs can be a potential source of antigens for the anti-breast cancer immunization and more investigations are necessary.