Abstract A62: Thymic aplasia and decreased immunologic function: Possible factors behind cancer development
Authors: Xu Jie , Xu Ze , zhu Shiping , Qio Shaoming , Mohamed Mona , Wu Bin 
Published: August 2014

Objective: The objective of this work was to investigate the relation of the immune system and the development of cancer.

Method: Over a 7-year period, 680 Kunming mice, age 8-10 weeks were included in this study. They were divided into 4 groups: 1) 140 controls, 2) 105 Mice had tumor cell inoculation in the armpit, 3) 105 Mice had tumor cell inoculation in their armpits and received 10 ml steroid injection (for 30 days) to lower the immune function, and 4) 330 Mice had tumor cell inoculation in the armpit after excision of their thymus.In group 4, the mice were anesthetized and their skin and muscles was incised along the second, third and fourth ribs to expose the thymus which was gently separated and was excised. Each mouse was then put in a separate cage and the mice were taken care of very carefully. We used H22 cells to make a unicell suspending liquid. After dyeing the cancer cells with lichenin and counting them (averaging 1x106/ml), we made the hypodermic inoculation of cancer cells with 0.2 ml normal saline which was then injected to the mice at the left side of their anterior armpit skin. We weighed the mouse every 3 days and measured the diameter of the tumor under their skin with Vernier caliper. We reserved the whole blood of each mouse (using heparin) to do lymphocyte conversion. The mice were then euthanized and the thymuses, spleen were then excised, weighed and their size and volumes were recorded.

Results: Group 3 and 4 showed cancer-bearing signs seven days after removing their thymus, and after receiving steroid injections. Cancer development was monitored and assessed by observing the injection site for tumor growth by monitoring the tumor sizes. Furthermore, the group of mice which received steroids showed progressive atrophy of the thymus on histology and advanced cancer The thymuses of the control group did not show progressive atrophy. The numbers of metastatic nodules in the liver in the group which received steroid injections were 35% more than the ones in the non-steroid injection mice group as compared to group 2 which received no steroid injections.In thymus- reserved group receiving steroids, the spleen showed initial increase in its size on the 7th day, but then decreased in its size on the 14th day.

Discussion: Thymus is the central immune organ in which T cells mature and develop and have a critical role in immune regulation. The occurrence and metastasis of the tumor have close connection with the thymus functions and spleen functions such as the thymus progressively atrophy during the tumors growth (1, 2, 3). Hiroshi et al (4) found that the IPSCs cells then generated fully active, cancer-specific T lymphocytes. It is well established that immune cells called T cells are naturally capable of destroying cancer cells and that this ability can be suppressed by the tumor (5). In addition, the tumor possibly secrets the immune inhibiting factors which function on the thymus and made it shrink which consequently caused loss of its function (6). The spleen was initially enlarged suggesting its reaction and response to inhibit the growth of the tumor in its early stage, however, at a later stage, the spleen regressed 50% .

Conclusion: Thymus resection and post steroid had lowered the immunologic function of the mice and are the main possible factors of cancer development. The occurrence and metastasis of cancer has an obvious relation with the immune function of the immune organs such as thymus, spleen.

Citation Format: Jie Xu, Ze Xu, Shiping zhu, Shaoming Qio, Mona Mohamed, Bin Wu. Thymic aplasia and decreased immunologic function: Possible factors behind cancer development. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr A62.