Human Leukemia Growth Inhibition by a Novel Retinoid

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DESCRIPTION (provided by applicant): 6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalene carboxylic acid (AHPN/CD437) belongs to a class of adamantyl retinoids (AR) that induce apoptosis through as yet undefined mechanism(s). We have now identified an AHPN analog 4-[3-(1-adamanyly)-4-hydroxyphenyl]-3-chlorocinnamic acid (3-CI-AHPC), which binds to, but does not activate, the retinoic acid nuclear receptors. 3-C1-AHPC displays decreased toxicity compared to AHPN but continues to display high efficacy in inhibiting human acute myelogenous leukemia (AML) cell growth in vitro and mouse AML cells in vivo. In addition, we have found that 3-C1-AHPC induces the expression of a novel protein termed CARP-1. We recently identified CARP-1 as an important regulator of apoptosis by the ARs. Hypothesis: In this proposal we hypothesize that 3-C1-AHPC and newly synthesized analogs are highly active in inhibiting the growth of human primary AML cells in NOD-SCID mice and thus represent potential therapeutic agents in the treatment of AML. In addition, we also hypothesize that 3-CL-AHPC/analog apoptosis signaling is through its activation of the important transcriptional regulator, NFkB, and CARP-l-mediated pathways. Our hypothesis is based on the following observations. 1) 3-CI-AHPC inhibits the growth of AML cells in a syngeneic mouse model, patient derived AML cells, and human AML cell lines. 2) Inhibition of NFkB activation or inhibition of CARP-1 expression blocks 3-C1-AHPC-mediated apoptosis. We will confirm our hypothesis by conducting the following specific aims. Aim 1: Synthesize new analogs of 3-C1-AHPC. Aim 2: Demonstrate that 3-C1-AHPC and its analogs inhibit in vivo growth of human primary AML cells in NOD-SCID mice and display reduced toxicity. Aim 3: Delineate the mechanism(s) by which 3-CI-AHPC enhances CARP-1 expression and CARP-l-dependent reduced topoisomerase lIa levels. Aim 4: Delineate the pathway by which 3-C1-AHPC activates NFkB and its role in apoptosis induction.