Extracellular matrix (ECM) macromolecules are major components of the tumor microenvironment and are involved in cancer progression-related processes including integrin mediated permissive proliferative co-signals. Unexpectedly, preliminary data in our laboratory indicate that the basement membrane ECM macromolecule, Laminin-332 (Ln-332), has an anti-proliferative effect on cancer cells. On further examination, growth inhibition by Ln-332 appears to be secondary to an integrin mediated process that shifts cancer cells out of Warburg-like- metabolism, itself required for fast proliferation. Thus, the carcinoma cell line 804G which secretes its own Ln-332 substrate, forms small tumors in kidney capsule xenografts. Knockdown (804G-kd) of either of two Ln-332 subunits leads to greatly decreased Ln-332 secretion. Injected in the subrenal capsule of athymic mice, 804G-kd cells form tumors >50 fold larger than 804G parental, in which markers of both increased proliferation (Ki-67) and glucose uptake (GLUT-1 surface expression) are detectable. To account for this drastic proliferative increase, we compared metabolic parameters. In 804G-kd we detected a shift toward aerobic glycolysis (Warburg---like metabolism) characterized by increased GLUT1 surface expression, increased NADPH/NADP ratio, increased glucose uptake and lactate production, all aerobic glycolysis landmarks. The aerobic glycolysis shift is reversed if 804G-kd cells are plated on exogenous Ln-332 substrates. Moreover, the shift is phenocopied in 804G cells by antibody-based inhibition of ?1but not by knockdown of ?4 integrin, suggesting that, of the two Ln-332 integrin receptors, ?3?1 but not ?6?4mediates Ln-332 metabolic effects. Taken together, these data support the concept that Ln-332 negatively regulates proliferation by metabolic reprogramming that prevents aerobic glycolysis. In this application, we focus on investigating molecular mechanisms that connect ECM-initiated signaling with metabolic enzyme networks, hoping to break new ground for new directions in cancer research.
In Aim 1, we will test the hypothesis that ?1 integrins negatively regulate proliferation by inhibiting Warburg-like metabolism.
In Aim 2, we will identify the molecular mechanism by which integrin ?3?1 downstream signaling negatively regulates aerobic glycolysis. If successful, this project will deepen existing knowledge of tumor growth regulation by the microenvironment, with the potential to create exciting opportunities for currently unforeseen cancer treatment strategies.
Cancer cells implement aerobic glycolysis metabolism (the Warburg effect) to support fast proliferation. Blocking Warburg metabolism is a logical target for cancer treatment, but avenues to this end are not obvious. This proposal will identify novel avenues for blocking Warburg, based on our novel observations that cancer cell adhesion to the ECM macromolecule, Ln-332, naturally inhibits Warburg.