The present invention addresses the problem of providing a proliferation inhibitor which can act on a cancer stem cell exhibiting resistance to existing anti-cancer agent therapy methods through the inhibition of proliferation of the cell or the apoptosis of the cell. A cancer stem cell proliferation inhibitor which contains a retinoid agonist, preferably tamibarotene, as a sole active ingredient or both the retinoid agonist and a rexinoid agonist, preferably bexarotene, as active ingredients, and which can enhance the effects of various anti-cancer agents when used in combination with each of the anti-cancer agents.本發明課題為提供一種增殖抑制劑，其係抑制現存抗癌劑治療法中表現出抵抗性的癌幹細胞之增殖，透過細胞凋亡來發揮作用。本發明為一種癌幹細胞之增殖抑制劑，其係以類視色素促效劑(宜為他米巴羅汀)單劑或其與類視色素合成物促效劑(宜為蓓薩羅丁)兩劑作為有效成分之癌幹細胞之增殖抑制劑，而且藉由併用各種抗癌劑來增強抗癌劑的效果。
