Immortalized epidermal keratinocytes (HaCaT cells), tumorigenic epidermal keratinocytes (Ras-transformed HaCaT), an epidermoid vulva carcinoma-derived cell line previously reported to contain nicotinic acid receptors (A-431), and a human squamous cell carcinoma cell line (SCC-25) express mRNA for both receptors (Fig. 3A). Here, HCAR2 is linked to squamous cell carcinoma.