Conversely, reduction of glucose uptake in malignant cells promoted the formation of organized and growth-arrested structures with basal polarity, and suppressed oncogenic pathways. differences between normal and malignant phenotypes could not be explained by HIF-1/2, AMPK, or mTOR pathways. Loss of epithelial integrity involved activation of RAP1 via exchange protein directly activated by cAMP (EPAC), involving also O-linked N-acetylglucosamine modification downstream of the hexosamine biosynthetic pathway. The former, in turn, was mediated by pyruvate kinase M2 (PKM2) interaction with soluble adenylyl cyclase. Our findings show that increased glucose uptake activates known oncogenic pathways to induce malignant phenotype, and provide possible targets for diagnosis and therapeutics. == Introduction == Traditionally, glucose intermediary metabolism was referred to as a housekeeping function (reviewed EML 425 in ref.1). However, the EML 425 role of aerobic glycolysis, referred to as the Warburg effect, is creating much excitement again in the field of cancer research. Warburg hypothesized that irreversible mitochondrial dysfunction is the underlying reason behind the metabolic shift to aerobic glycolysis, which results in transformation of the cells (2). But mitochondrial dysfunction need not always be present in transformed cells when there is increased aerobic glycolysis (35). Still, much of the current literature views the metabolic alterations as resulting from the pleiotropic response to oncogenic signaling (reviewed in refs.68). Furthermore, the most frequently mentioned reasons for increased glucose metabolism are contributions to the tumors proliferation and survival: the glycolytic pathway provides ATP independently of oxygen when tumors confront a hypoxic microenvironment (9). Numerous intermediary glucose metabolites are used for diverse biosynthetic processes (7), and NADPH, a reducing equivalent generated by glucose metabolism, sequesters ROS and thus confers resistance to cell death (10,11). Yet although Warburg had theorized that the metabolic shift to glycolysis is the origin of cancer cells (2), the demonstration of causative effects of the increased glucose uptake and metabolism on oncogenesis has eluded the field so far (3,12). In contrast, the idea that glucose level itself can trigger intra- and intercellular signaling is accepted and studied widely in the EML 425 fields of endocrinology and diabetes. Glucose signaling is known to be linked to physiological and pathological events, such as regulation of hormone secretion and insulin resistance (1214). Given the demonstration of the effect of the microenvironment, including tissue architecture (15) and the composition of the media (1), on gene expression, and the integration of signaling events observed in 3D laminin-rich ECM (lrECM) gel assays (reviewed in ref.16), we reasoned that glucose uptake and metabolism should also be essential components of the tissues integration plan that is, if uptake and metabolism of glucose were hyperactivated, the canonical oncogenic pathways should also be activated reciprocally. Here, we directly addressed this important possibility in cancer promotion using 3D lrECM cultures, in which both malignant and nonmalignant breast epithelial cells behave phenotypically analogous to their corresponding architecture in vivo (17). Our observations showed that inhibition EML 425 of glucose uptake and metabolism suppressed known oncogenic pathways and resulted in phenotypic reversion (16) in a number of breast EML 425 cancer cells in the 3D assays. Importantly, forced increases in glucose uptake and metabolism activated a number of such signaling pathways involved in oncogenesis, leading to a malignant-like phenotype in nonmalignant breast cells. We showed that both the glycolytic pathway and the hexosamine biosynthetic pathway (HBP) were involved in the reciprocal regulation but, importantly, only in a 3D structure, not on tissue culture plastic (i.e., 2D). These findings strongly suggest that increased glucose uptake and metabolism in nonmalignant/premalignant cells could indeed be an oncogenic event analogous to activation of EGFR, 1 integrin (encoded byITGB1), PI3K-AKT, Flrt2 or MEK-ERK. We also unraveled the mechanisms of the intricate and hitherto unknown reciprocal activation by which glucose metabolism and other oncogenic pathways integrate in 3D. == Results == == Increased glucose metabolism activates pathways involved in oncogenesis. == To test whether increased glucose metabolism itself is required for oncogenic signaling, we used 3D lrECM cultures of HMT-3522, a breast cancer progression series that includes nonmalignant (S1) and malignant (T4-2) human breast epithelial cells from the same reduction mammoplasty (18). We previously used this assay to describe the involvement and reciprocity among a number of oncogenic signaling pathways and cellular contexts (16,1926). We have also described how suppressing activated signaling in any one such pathway in the 3D assay adjusts all the others, leading to phenotypic reversion, in which cancer cells perceive microenvironmental cues that lead to the formation of acinus-like structures, as seen in primary nonmalignant cells (16,1926). In the present study, we used phenotypic reversion of cancer cells as an assay with which to test our hypothesis that the signaling integration plan of the breast-like acini involves reciprocal regulation of glucose metabolism as well (Figure1A and Supplemental Figure.