A paradox in medical oncology has long existed that although the majority of human cancers have acquired a deficiency in apoptosis, certain chemotherapeutic agents such as DNA alkylating agents remain the most effective means of treating cancer patients by inducing cancer cell death. This suggests that alternative cell death pathways may be involved. These may include necrosis and autophagic cell death. One fundamental difference between cancer and normal cells is their biochemical metabolism. Tumor cells display an abnormal propensity for growth and proliferation, thus are in net need of energy source for biosynthesis. This may render cancer cells more susceptible to the perturbation of cell metabolism. Several oncoproteins, such as c- myc, Akt, and Ras, have been shown to promote cell growth by regulating cell metabolism, and thus may prime cells to cell death induced by bioenergetic failure. We propose to explore the hypothesis that targeting cellular metabolism can be a strategy to kill cancer cells that often have crippled apoptosis machinery. We will also study whether and how certain oncoproteins such as c-myc, Akt, and Ras may differentially affect cell metabolism and render cells susceptible to the perturbation of cell metabolism, and study how tumor cells may respond to metabolic stress by inducing autophagy. We will: 1) Study the hypothesis that cell death can be induced in apoptosis-deficient cells by metabolic perturbation resulting from DNA alkylating damage. Our preliminary data indicates that necrosis can be induced by DNA alkylating damage as a result of the inhibition of glycolysis, which is caused by the NAD depletion resulting from the activation of a nuclear enzyme PARP. We will further examine this theory in vitro and in vivo, and will study the pro-inflammatory response triggered by this non-apoptotic cell death. 2). Study the role of autophagy in cancer cells treated with chemotherapeutic agents. As an important cellular response to nutrient starvation and stress, autophagy has been shown to have opposite effects on cell survival and cell death. These opposing effects of autophagy may on one hand contribute to cancer cell death, on the other hand, to cancer cell resistance to therapy. We will study in this Aim whether and how DNA alkylating damage can induce autophagy, and how autophagy interplays with other forms of cell death. 3). Study the hypothesis that oncoproteins such as c-myc, Ras, and Akt can affect cell metabolism and prime cancer cells to die from bioenergetic failure. c-myc, Ras, and Akt oncoproteins are involved in cell growth, proliferation, and death. These proteins have been shown to regulate cell metabolism thus promoting cancer cell anabolic processes, however maybe through different mechanisms. We plan to express specific oncogenes in genetically defined murine cells as well as human cancer cells to study how they may differentially affect cellular metabolism, with respect to their ability to prime cancer cells to die of metabolic perturbation.
A major strategy for treating cancer is to selectively induce cancer cell death. Most human cancers evolved as a result of the loss of ability to die by apoptosis, and have acquired specific needs for cell metabolism. The overall goal of this project is to study how non-apoptotic cell death can be induced by chemotherapy, and by the inhibition of cell metabolism, thus targeting cell metabolism can be harnessed to treat cancer patients by inducing cancer cell specific death.
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