CysLTs contribute to cancer progression and several observations support a pro-tumorigenic effect of LTD4 via CysLT1 in colorectal cancer.307 Montelukast is a CysLT1 receptor antagonist already used in asthma treatment.308 Interestingly, asthma patients treated with montelukast have a considerably lower risk to develop cancer.309 In animal studies, montelukast increased survival rates in a spontaneous metastasis model of Lewis lung carcinoma (LLC) and delayed tumor growth.308,310. This evidence concerns the gene CYSLTR1 and cancer.