Figure 4.

Possible mechanism of choriocarcinoma chemotherapy and chemosensitization role of thyroid hormone in breast cancer. Choriocarcinoma has better chemotherapeutic efficacy, the possible cause may be related with high HCG releasing when most choriocarcinoma cells (CC) are killed by chemotherapy, besides those stay in low metabolism level, which permits them from cytotoxicity effect on some level. As HCG has TSH like effect, thyroid hormone increases and promotes CC retardant in G0 phase stepping into cell division cycle, which makes CC more sensitive to chemotherapy. However, in breast cancer, thyroid hormone decreasing occurs in most breast cancer patients when chemotherapy is applied, but there is no spontaneous complement of thyroid hormone in microenviroment of breast cancer cells (BC). The absence or lack of thyroid hormone may induce G0 arrest, which makes residual BC insensitive to subsequent chemotherapy. So, inexistence of thyroid hormone decreasing in choriocarcinoma, even thyroid hormone increasing during chemotherapy, inspires us to imitate this thyroid hormone changing model in breast cancer. As we expect, the chemosensitivity can be enhanced by adding thyroid hormone before and / or during chemotherapy, which is elaborately illustrated in our cell based experiment.