This technology includes the utility of the novel small molecule inhibitors of ALDH1A1 (RALDH1) in combination with immunotherapy for the treatment of hepatocellular carcinoma (HCC). Recently it was shown that the ALDH1A1 catalyzed production of retinoic acid (RA) in tumor cells promotes their differentiation into immunosuppressive antigen-presenting cells. Therefore, blocking RA production by tumor cells and/or blocking RA signaling in monocytes using our ALDH1A1 inhibitors can alleviate immunosuppression and engender anti-tumor immune responses.