Chemoprevention of lung cancer with mitochondria-targeted honokiol

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Project Summary: Non-small-cell lung cancers (NSCLCs) are the most common lung cancers, accounting for 85% of all lung cancer cases in the United States. Cigarette smoking is the predominant cause of this disease and former smokers remain at elevated risk. About 40% of NSCLCs are adenocarcinomas (LUAD). The number of LUAD cases in former smokers is expected to rise. Chemoprevention of LUAD development in at-risk populations such as former smokers is an important strategy to reduce NSCLCs mortality. Furthermore, metastasis of LUAD to the brain is one of the leading causes of mortality. Thus, discovering new strategies to prevent primary and metastatic LUAD is critically important. Because patients who will receive preventive treatment do not have overt disease, such treatments must not only be effective but also have a very low risk of side effects. Honokiol (HNK), a natural compound present in magnolia bark extracts, has a favorable safety profile and has been shown to prevent the development of several types of cancer in animal models. We have recently demonstrated potent efficacy of HNK in the chemoprevention of lung tumorigenesis in mice. Analysis of HNK’s mechanism of action suggests that its effect is primarily mediated by inducing apoptosis through a mitochondria-dependent mechanism. This provides a supportive rationale for conjugating HNK to a targeting agent that drives it into mitochondria in order to dramatically increase its chemopreventive efficacy. Preliminary data demonstrate that mitochondria-targeted HNK (Mito-HNK) is also a significantly more potent chemopreventive agent of LUAD brain metastasis (a common clinical feature of the disease) than HNK. We hypothesize that Mito-HNK is a novel, potent chemopreventive agent of LUAD progression and metastasis and acts primarily through novel mitochondrial mechanisms. This hypothesis will be tested in three specific aims. Aim 1 will evaluate the chemopreventive potential and mechanisms of action of Mito-HNK in vitro. Aim 2 will determine the chemopreventive efficacy of Mito-HNK on lung tumor progression in A/J mice. Aim 3 will determine the chemopreventive efficacy of Mito-HNK on LUAD brain metastasis. We will use state-of-the-art small animal imaging technology to monitor the growth of primary tumors (magnetic resonance imaging) and engraftment of metastatic cells as well as innovative approaches for in vivo monitoring of the changes in cancer cell bioenergetics and cellular oxidant production (bioluminescent imaging). This will enable precise and accurate monitoring of the efficacy of Mito-HNK in distinct stages of tumorigenesis. The clinical impact of developing a novel, potent agent for LUAD chemoprevention will be highly significant. The knowledge generated from this proposal could be used to direct the course of future clinical trials and may guide the development of an entirely new class of agents for LUAD chemoprevention.