Most cancer cells predominantly produce energy by glycolysis rather than oxidative phosphorylation via the tricarboxylic acid (TCA) cycle, even in the presence of an adequate oxygen supply (Warburg effect). However, little has been reported regarding the direct measurements of global metabolites in clinical tumor tissues. Here, we applied capillary electrophoresis time-of-flight mass spectrometry, which enables comprehensive and quantitative analysis of charged metabolites, to simultaneously measure their levels in tumor and grossly normal tissues obtained from 16 colon and 12 stomach cancer patients. Quantification of 94 metabolites in colon and 95 metabolites in stomach involved in glycolysis, the pentose phosphate pathway, the TCA and urea cycles, and amino acid and nucleotide metabolisms resulted in the identification of several cancer-specific metabolic traits. Extremely low glucose and high lactate and glycolytic intermediate concentrations were found in both colon and stomach tumor tissues, which indicated enhanced glycolysis and thus confirmed the Warburg effect. Significant accumulation of all amino acids except glutamine in the tumors implied autophagic degradation of proteins and active glutamine breakdown for energy production, i.e., glutaminolysis. In addition, significant organ-specific differences were found in the levels of TCA cycle intermediates, which reflected the dependency of each tissue on aerobic respiration according to oxygen availability. The results uncovered unexpectedly poor nutritional conditions in the actual tumor microenvironment and showed that capillary electrophoresis coupled to mass spectrometry-based metabolomics, which is capable of quantifying the levels of energy metabolites in tissues, could be a powerful tool for the development of novel anticancer agents that target cancerspecific metabolism. [Cancer Res 2009;69(11):4918-25]

BACKGROUND Head and neck squamous cell carcinoma typically is diagnosed at an advanced stage, and the prognosis for patients with this type of malignancy is poor. Detection of these lesions at an earlier stage (e.g., as carcinoma in situ) would be of clear benefit to patients. However, it has been extremely difficult to detect carcinoma in situ at head and neck mucosal sites during routine endoscopy, even after numerous passes of the endoscope through the oral cavity and the pharynx. METHODS The current clinical investigation was performed during routine endoscopic screening or surveillance procedures. The authors used a novel optical technique, known as narrowband imaging (NBI) that allows noninvasive visualization of the microvascular structure of an organ's surface using reflected light. RESULTS Between April 2002 and August 2003, 34 consecutive superficial lesions were found in 18 patients. Multifocal carcinoma was found in 5 patients (28%). The median age of the patients examined was 59.5 years (range, 43–71 years), and 83% of all patients were male. All lesions exhibited a microvascular proliferation pattern on magnified NBI. Thirteen patients with a combined total of 29 lesions underwent endoscopic resection under general anesthesia. The pyriform sinus was the most frequent primary site (66%; 19 of 29 lesions). The median tumor diameter was 20 mm (range, 1.3–40 mm). Twenty‐one lesions (72%) were histologically confirmed to be carcinoma in situ, and the remaining lesions showed evidence of microinvasion (0.05–1 mm) beneath the epithelium. Vascular invasion was observed in only one lesion. The median hospital stay was 10 days (range, 4–18 days). All patients were discharged without severe complications. After a median follow‐up period of 8 months (range, 1–16 months), there were no cases of local disease recurrence. CONCLUSION The authors stress the importance of endoscopic detection of superficial carcinoma at oropharyngeal and hypopharyngeal mucosal sites. NBI is a promising and potentially powerful tool for identifying carcinomas at an earlier stage during routine endoscopic examination. Cancer 2004. © 2004 American Cancer Society.

Tumor cells generally proliferate rapidly and the demand for essential nutrients as well as oxygen always exceeds the supply due to the unregulated growth and the insufficient and inappropriate vascular supply. However, cancer cells show an inherent ability to tolerate extreme conditions, such as that characterized by low nutrient and oxygen supply, by modulating their energy metabolism. Thus, targeting nutrientdeprived cancer cells may be a novel strategy in anticancer drug development. Based on that, we established a novel screening method to discover anticancer agents that preferentially inhibit cancer cell viability under the nutrientdeprived condition. After screening 500 medicinal plant extracts used in Japanese Kampo medicine, we found that a CH 2 Cl 2 -soluble extract of Arctium lappa exhibited 100% preferential cytotoxicity under the nutrient-deprived condition at a concentration of 50 Mg/mL with virtually no cytotoxicity under nutrient-rich condition. Further bioassayguided fractionation and isolation led to the isolation of arctigenin as the primary compound responsible for such preferential cytotoxicity; the compound exhibited 100% preferential cytotoxicity against nutrient-deprived cells at a concentration of 0.01 Mg/mL. Furthermore, arctigenin was also found to strongly suppress the PANC-1 tumor growth in nude mice, as well as the growth of several of the tested pancreatic cancer cell lines, suggesting the feasibility of this novel antiausterity approach in cancer therapy. Further investigation of the mechanism of action of arctigenin revealed that the compound blocked the activation of Akt induced by glucose starvation, which is a key process in the tolerance exhibited by cancer cells to glucose starvation.

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), which is produced during cooking and is mutagenic to bacteria and cultured mammalian cells, was found to induce high incidences of colon and mammary carcinomas in F344 rats when administered at a concentration of 400 p.p.m. in the diet for 52 weeks. Since PhIP is the most abundant of the mutagenic heterocyclic amines in cooked meat and fish, the compound might be related to malignancies of the colon and breast in humans.

Several types of cancer cells, including colorectal cancerderived cell lines, show austerity, the resistance to nutrient starvation, but exactly how cancer cells obtain energy sources under conditions in which their external nutrient supply is extremely limited remains to be clarified. Because autophagy is a catabolic process by which cells supply amino acids from self-digested organelles, cancer cells are likely to use autophagy to obtain amino acids as alternative energy sources. Amino acid deprivation-induced autophagy was assessed in DLD-1 and other colorectal cancer-derived cell lines. The autophagosome-incorporated LC3-II protein level increased after treatment with a combination of autolysosome inhibitors, which interferes with the consumption of autophagosomes. Autophagosome formation was also morphologically confirmed using ectopically expressed green fluorescent protein-LC3 fusion proteins in DLD-1 and SW480 cells. These data suggest that autophagosomes were actively produced and promptly consumed in colorectal cancer cells under nutrient starvation. Autolysosome inhibitors and 3-methyl adenine, which suppresses autophagosome formation, remarkably enhanced apoptosis under amino acid-deprived and glucosedeprived condition. Similar results were obtained in the cells with decreased ATG7 level by the RNA interference. These data suggest that autophagy is pivotal for the survival of colorectal cancer cells that have acquired austerity. Furthermore, autophagosome formation was seen only in the tumor cells but not in the adjacent noncancerous epithelial cells of colorectal cancer specimens. Taken together, autophagy is activated in colorectal cancers in vitro and in vivo, and autophagy may contribute to the survival of the cancer cells in their microenvironment. [Cancer Res 2007;67(20):9677-84]