ERBB2 and breast carcinoma: When incubated in the absence of serum, THCA-A exhibited good efficacy and potency at reducing PCC viability in the 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assay.14 This agrees with previous results by the same group, where THCA-A was also efficacious at inhibiting proliferation of two different human breast carcinoma (HBC) cells, triple-negative MDA-MB-231 and HER2-negative MCF-7.13 Although activation of CB1 receptors inhibits tumor growth and metastasis of breast cancer,46 the mechanism underlying the antineoplastic actions of THCA-A remains unknown.