The synthesis and in vitro and in vivo anti-breast and anti-prostate cancers activities of novel C-4 heteroaryl 13-cis retinamides that modulate Mnk-eIF4E and AR signaling are discussed. In both breast and prostate cancer cell lines, these compounds induce Mnk1/2 degradation to substantially suppress eIF4E phosphorylation. In prostate cancer cells, the compounds induce degradation of both full-length androgen receptor (fAR) and splice variant AR (AR-V7) to inhibit AR transcriptional activity. The consequences of these multiple activities resulted in inhibition of cell growth and migration and induction of apoptosis. Finally and importantly, the compounds demonstrate strong in vitro and in vivo anti-breast and anti-prostate cancer activities, with no apparent host toxicities.