Some authors supposed the relevance of environment in minimizing cancer growth and reported that α-pinene has no inhibitory effect on melanoma cell proliferation in vitro, but indicated activation in the hypothalamus/sympathetic nerve/leptin axis tumor growth (decreased plasma leptin concentration) and in the immune system (increased the numbers of B cells, CD4+ T cells, CD8+ T cells, and NK cells) as possible mechanisms through which exposure to a fragrant environment containing α-pinene suppressed B16 tumor growth in C57BL/6 mice [205,206]. Here, CD4 is linked to neoplasm.