CNR1 and neoplasm: Conversely, a recent study has demonstrated that the CB1 agonist arachidonyl-2’-chloroethylamide (ACEA), the selective CB2 agonist HU308 and THC promoted rather than inhibited the progression of human papillomavirus-positive squamous cell carcinomas of the head and neck, with THC-treated tumour xenografts growing faster than controls [55].