Such differential effects have been previously reported, with Δ9-THC eliciting the proliferation of neural progenitors (Galve-Roperh et al., 2013) and of human breast carcinoma cell lines (Takeda et al., 2008) but suppressing the proliferation of activated CD4+ T cells (Yang et al., 2016) and of non-small cell lung cancer cells (Preet et al., 2008). The gene discussed is CD4; the disease is breast carcinoma.