Abstract: The present disclosure provides methods and composition for treating multi-drug resistant cancers, in particular, breast cancers, via administration to a subject the composition including a peptide having a sequence complementary to a highly conserved motif present in substantially all integrins responsible for an integrin-mediated attachment-independent chemoresistance to one or more chemotherapeutic agents. The binding of the sequence of the peptide to the highly conserved motif will enhance accumulation of the chemotherapeutic agents in the tumor-initiating cells and in turn restores the function of the chemotherapeutic agents in the tumor-initiating cells.

Abstract: The present disclosure provides methods and composition for treating multi-drug resistant cancers, in particular, breast cancers, via administration to a subject the composition including a peptide having a sequence complementary to a highly conserved motif present in substantially all integrins responsible for an integrin-mediated attachment-independent chemoresistance to one or more chemotherapeutic agents. The binding of the sequence of the peptide to the highly conserved motif will enhance accumulation of the chemotherapeutic agents in the tumor-initiating cells and in turn restores the function of the chemotherapeutic agents in the tumor-initiating cells.

Abstract: (?)-EGCG, the most abundant catechin, was found to be chemopreventive and anticancer agent. However, (?)-EGCG has at least one limitation: it gives poor bioavailability. This invention provides compounds of generally formula 10, wherein R1 is selected from the group of —H and C1 to C6 acyl group; R2, R3, and R4 are each independently selected from the group of —H, —OH, and C1 to C6 acyloxyl group; and at least one of R2, R3, or R4 is —H. The derivatives of (?)-EGCG that is at least as potent as (?)-EGCG. The carboxylate protected forms of (?)-EGCG and its derivatives are found to be more stable than the unprotected forms, which can be used as proteasome inhibitors to reduce tumor cell growth.