Human lung carcinomas synthesize immunoregulatory glucocorticoids.

The need for new options in lung cancer treatment inevitably leads back to basic research. The tumor itself and the tumor environment especially the interaction with the immune system need to be better understood to develop targeted therapies. In the context of lung cancer glucocorticoids (GC) are mainly known as a combination drug to attenuate side-effects of chemotherapies. However, endogenous extra-adrenal GC have been shown to substantially regulate local immune responses within various tissues, including the lung. In this study we investigated whether primary lung tumors have maintained the capacity to synthesize GC and may thereby regulate anti-tumor immune responses. We show that several non-small cell lung carcinoma (NSCLC) and small cell lung carcinoma (SCLC) cell lines express key steroidogenic enzymes and synthesize bioactive GC under steady state conditions. We also show that tumor-derived GC can inhibit splenic T cell activation, thus demonstrating their immunoregulatory potential. Moreover, steroidogenic enzymes were detected by quantitative RT-PCR and immunohistochemistry in tissue sections of different human lung tumors, further strengthening the idea that human lung carcinomas regulate their microenvironment by releasing immunoregulatory GC, which potentially contributes to immune evasion and treatment resistance.