1. Ferlay J, Soerjomataram I, Dikshit R, Eser S, Mathers C, Rebelo M, et al. Cancer incidence and mortality worldwide: sources, methods and major patterns in GLOBOCAN 2012. Int J Cancer. 2015;136:E359–E386.
2. Al-Hajj M, Wicha MS, Benito-Hernandez A, Morrison SJ, Clarke MF. Prospective identification of tumorigenic breast cancer cells. Proc Natl Acad Sci USA. 2003;100:3983 –3988.
3. Singh SK, Hawkins C, Clarke ID, Squire JA, Bayani J, Hide T, et al. Identification of human brain tumour initiating cells. Nature. 2004;432:396–401.
4. Collins AT, Berry PA, Hyde C, Stower MJ, Maitland NJ. Prospective identification of tumorigenic prostate cancer stem cells. Cancer Res. 2005;65:10946–10951.
5. Dalerba P, Dylla SJ, Park IK, Liu R, Wang X, Cho RW, et al. Phenotypic characterization of human colorectal cancer stem cells. Proc Natl Acad Sci USA. 2007;104:10158–10163.
6. Ishimoto T, Nagano O, Yae T, Tamada M, Motohara T, Oshima H, et al. CD44 variant regulates redox status in cancer cells by stabilizing the xCT subunit of system xc(-) and thereby promotes tumor growth. Cancer Cell. 2011;19:387–400.
7. Brigelius-Flohé R, Maiorino M. Glutathione peroxidases. Biochim Biophys Acta. 2013;1830:3289–3303.
8. Gorrini C, Harris IS, Mak TW Modulation of oxidative stress as an anticancer strategy. Nat Rev Drug Discov. 2013;2:931–947.
9. Tsuchihashi K, Okazaki S, Ohmura M, Ishikawa M, Sampetrean O, Onishi N, et al. The EGF receptor promotes the malignant potential of glioma by regulating amino acid transport system xc(-). Cancer Res. 2016;76:2954–2963.
10. Yasui W, Kudo Y, Naka K, Fujimoto J, Ue T, Yokozaki H, et al. Expression of CD44 containing variant exon 9 (CD44v9) in gastric adenomas and adenocarcinomas: relation to the proliferation and progression. Int J Oncol. 1998;12:1253–1258.
11. Hirata K, Suzuki H, Imaeda H, Matsuzaki J, Tsugawa H, Nagano O, et al. CD44 variant 9 expression in primary early gastric cancer as a predictive marker for recurrence. Br J Cancer. 2013;109:379–386.
12. Go SI, Ko GH, Lee WS, Kim RB, Lee JH, Jeong SH, et al. CD44 variant 9 serves as a poor prognostic marker in early gastric cancer, but not in advanced gastric cancer. Cancer Res Treat. 2016;48:142–152.
13. Japanese Gastric Cancer Association. Japanese classification of gastric carcinoma: 3rd English edition. Gastric Cancer. 2011;14:101–112.
14. Aso T, Matsuo M, Kiyohara H, Taguchi K, Rikimaru F, Shimokawa M, et al. Induction of CD44 variant 9-expressing cancer stem cells might attenuate the efficacy of chemoradioselection and worsens the prognosis of patients with advanced head and neck cancer. PLoS One. 2015;10:e0116596.
15. Lei Z, Tian D, Zhang C, Zhao S, Su M. Clinicopathological and prognostic significance of GPX2 protein expression in esophageal squamous cell carcinoma. BMC Cancer. 2016;16:410.
16. Kimura Y, Goi T, Nakazawa T, Hirono Y, Katayama K, Urano T, et al. CD44 variant exon 9 plays an important role in colon cancer initiating cells. Oncotarget. 2013;4:785–791.
17. Kobayashi K, Matsumoto H, Matsuyama H, Fujii N, Inoue R, Yamamoto Y, et al. Clinical significance of CD44 variant 9 expression as a prognostic indicator in bladder. Oncol Rep. 2016;36:2852 –2860.
18. Trachootham D, Alexandre J, Huang P. Targeting cancer cells by ROS-mediated mechanisms: a radical therapeutic approach? Nat Rev Drug Discov. 2009;8:579–591.
19. Nagano O, Okazaki S, Saya H. Redox regulation in stem-like cancer cells by CD44 variant isoforms. Oncogene. 2013;32:5191–5198.
20. Aruffo A, Stamenkovic I, Melnick M, Underhill CB, Seed B. CD44 is the principal cell surface receptor for hyaluronate. Cell. 1990;61:1303–1313.
21. Ponta H, Sherman L, Herrlich PA. CD44: from adhesion molecules to signalling regulators. Nat Rev Mol Cell Biol. 2003;4:33–45.
22. Zöller M. CD44: can a cancer-initiating cell profit from an abundantly expressed molecule? Nat Rev Cancer. 2011;11:254–267.
23. Tanabe KK, Ellis LM, Saya H. Expression of CD44R1 adhesion molecule in colon carcinomas and metastases. Lancet. 1993;341:725–726.
24. Rall CJ, Rustgi AK. CD44 isoform expression in primary and metastatic pancreatic adenocarcinoma. Cancer Res. 1995;55:1831–1835.
25. Muramaki M, Miyake H, Kamidono S, Hara I. Over expression of CD44V8-10 in human bladder cancer cells decreases their interaction with hyaluronic acid and potentiates their malignant progression. J Urol. 2004;171:426–430.
26. Taniguchi D, Saeki H, Nakashima Y, Kudou K, Nakanishi R, Kubo N, et al. CD44v9 is associated with epithelial-mesenchymal transition and poor outcomes in esophageal squamous cell carcinoma. Cancer Med. 2018;7:6258-6268.
27. Yamakawa Y, Kusuhara M, Terashima M, Kinugasa Y, Sugino T, Abe M, et al. CD44 variant 9 expression as a predictor for gastric cancer recurrence: immunohistochemical and metabolomic analysis of surgically resected tissues. Biomed Res. 2017;38:41-52.
28. Warzecha CC, Sato TK, Nabet B, Hogenesch JB, Carstens RP. ESRP1 and ESRP2 are epithelial cell-type-specific regulators of FGFR2 splicing. Mol Cell. 2009;33:591–601.
29. Yae T, Tsuchihashi K, Ishimoto T, Motohara T, Yoshikawa M, Yoshida GJ, et al. Alternative splicing of CD44 mRNA by ESRP1 enhances lung colonization of metastatic cancer cell. Nat Commun. 2013;3:883.
30. Longley DB, Harkin DP, Johnston PG. 5-fluorouracil: mechanisms of action and clinical strategies. Nat Rev Cancer. 2003;3:330–338.
31. Chen RS, Song YM, Zhou ZY, Tong T, Li Y, Fu M, et al. Disruption of xCT inhibits cancer cell metastasis via the caveolin-1/beta-catenin pathway. Oncogene. 2009;28:599–609.
32. Shitara K, Doi T, Nagano O, Imamura CK, Ozeki T, Ishii Y, et al. Dose-escalation study for the targeting of CD44v+ cancer stem cells by sulfasalazine in patients with advanced gastric cancer (EPOC1205). Gastric Cancer. 2017;20:341–349.
33. Shitara K, Doi T, Nagano O, Fukutani M, Hasegawa H, Nomura S, et al. Phase 1 study of sulfasalazine and cisplatin for patients with CD44v-positive gastric cancer refractory to cisplatin (EPOC1407). Gastric Cancer. 2017;20:1004–1009.
34. Otsubo K, Nosaki K, Imamura CK, Ogata H, Fujita A, Sakata S, et al. Phase I study of salazosulfapyridine in combination with cisplatin and pemetrexed for advanced non-small-cell lung cancer. Cancer Sci. 2017;108:1843–1849.
35. Kodama H, Murata S, Ishida M, Yamamoto H, Yamaguchi T, Kaida S, et al. Prognostic impact of CD44-positive cancer stem-like cells at the invasive front of gastric cancer. Br J Cancer. 2017;116:186–194.