TDO2 and squamous cell carcinoma: In a preclinical study, Tsai-Der Chuang et al. found that treatment with 680C91 in immunodeficient mice bearing human fibrosarcoma xenografts reduced the weight of uterine fibroid xenografts by 30% [109] S. Hu et al. discovered that in a squamous cell carcinoma mouse model, the TDO2 inhibitor LM10 alleviated T cell suppression, restored T cell anti-tumor responses, and blocked the malignant progression of squamous cell carcinoma [110].