The CD44 isoform containing variant exon v6 (CD44v6) plays an important role in the progression, metastasis, and prognosis of colorectal cancer (CRC). Recently, it was found that CD44v6 is involved in acquired drug resistance. This study aimed to investigate the molecular mechanism of CD44v6 in the resistance of CRC cells to chemotherapy. A stable CD44v6 overexpression model in SW480 cells was established via lentiviral transduction. The chemosensitivity of cells to 5-fluorouracil (5-FU) and oxaliplatin (L-OHP) was determined by cell counting kit (CCK)-8, lactate dehydrogenase (LDH) release, and colony formation assays. Immunohistochemical staining of CD44v6 was performed in human CRC tissues. The key components in cell apoptosis, drug efflux and metabolism, mismatch repair, autophagy, epithelial–mesenchymal transition (EMT), and the PI3K–Akt and MAPK–Ras–Erk1/2 pathways were assessed using flow cytometry, quantitative real-time polymerase chain reaction (PCR), and western blot assays. The CD44v6 overexpression cells showed a higher viability, a lower LDH release rate, and an increased clonogenicity than the control cells under drug treatment. Moreover, overexpression of CD44v6 resulted in enhanced autophagy flux, EMT, and phosphorylation of Akt and Erk in the presence of drugs. Furthermore, high CD44v6 expression in the primary tumor was closely associated with an early recurrence in CRC patients who underwent curative surgery and adjuvant chemotherapy. In conclusion, overexpression of CD44v6 contributes to chemoresistance in SW480 cells under cytotoxic stress via the modulation of autophagy, EMT, and activation of the PI3K–Akt and MAPK–Ras–Erk pathways.
CD44v6 Colorectal cancer Chemoresistance Autophagy
This is a preview of subscription content, log in to check access.
This work was supported by the Science Foundation from the Health Bureau of Wenzhou City of Zhejiang, China (Y20140713) and by the Incubation Program from The First Affiliated Hospital of Wenzhou Medical University (FHY2014013).
McCubrey JA, Steelman LS, Kempf CR, Chappell WH, Abrams SL, Stivala F, et al. Therapeutic resistance resulting from mutations in Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR signaling pathways. J Cell Physiol. 2011;226(11):2762–81. doi:10.1002/jcp.22647.CrossRefPubMedGoogle Scholar
Sui H, Zhu L, Deng WL, Li Q. Epithelial-mesenchymal transition and drug resistance: role, molecular mechanisms, and therapeutic strategies. Oncol Res Treat. 2014;37(10):584–9. doi:10.1159/000367802.CrossRefPubMedGoogle Scholar
Todaro M, Gaggianesi M, Catalano V, Benfante A, Iovino F, Biffoni M, et al. CD44v6 is a marker of constitutive and reprogrammed cancer stem cells driving colon cancer metastasis. Cell Stem Cell. 2014;14(3):342–56. doi:10.1016/j.stem.2014.01.009.CrossRefPubMedGoogle Scholar
Klionsky DJ, Abdalla FC, Abeliovich H, Abraham RT, Acevedo-Arozena A, Adeli K, et al. Guidelines for the use and interpretation of assays for monitoring autophagy. Autophagy. 2012;8(4):445–544.CrossRefPubMedPubMedCentralGoogle Scholar
Yanamoto S, Yamada S, Takahashi H, Naruse T, Matsushita Y, Ikeda H, et al. Expression of the cancer stem cell markers CD44v6 and ABCG2 in tongue cancer: effect of neoadjuvant chemotherapy on local recurrence. Int J Oncol. 2014;44(4):1153–62. doi:10.3892/ijo.2014.2289.PubMedGoogle Scholar
Costa S, Terzano P, Bovicelli A, Martoni A, Angelelli B, Santini D, et al. CD44 isoform 6 (CD44v6) is a prognostic indicator of the response to neoadjuvant chemotherapy in cervical carcinoma. Gynecol Oncol. 2001;80(1):67–73. doi:10.1006/gyno.2000.6016.CrossRefPubMedGoogle Scholar
Bendardaf R, Lamlum H, Ristamaki R, Pyrhonen S. CD44 variant 6 expression predicts response to treatment in advanced colorectal cancer. Oncol Rep. 2004;11(1):41–5.PubMedGoogle Scholar
Niu RF, Zhang J, Huang JY. Expression of CD44v6 before and after chemotherapy in patients with breast cancer and its significance. Ai Zheng. 2002;21(1):71–4.PubMedGoogle Scholar
Recio JA, Merlino G. Hepatocyte growth factor/scatter factor induces feedback up-regulation of CD44v6 in melanoma cells through Egr-1. Cancer Res. 2003;63(7):1576–82.PubMedGoogle Scholar
Quinones A, Dobberstein KU, Rainov NG. The egr-1 gene is induced by DNA-damaging agents and non-genotoxic drugs in both normal and neoplastic human cells. Life Sci. 2003;72(26):2975–92.CrossRefPubMedGoogle Scholar
Hebbard L, Steffen A, Zawadzki V, Fieber C, Howells N, Moll J, et al. CD44 expression and regulation during mammary gland development and function. J Cell Sci. 2000;113(Pt 14):2619–30.PubMedGoogle Scholar
Misra S, Ghatak S, Toole BP. Regulation of MDR1 expression and drug resistance by a positive feedback loop involving hyaluronan, phosphoinositide 3-kinase, and ErbB2. J Biol Chem. 2005;280(21):20310–5. doi:10.1074/jbc.M500737200.CrossRefPubMedGoogle Scholar
Park JM, Huang S, Wu TT, Foster NR, Sinicrope FA. Prognostic impact of Beclin 1, p62/sequestosome 1 and LC3 protein expression in colon carcinomas from patients receiving 5-fluorouracil as adjuvant chemotherapy. Cancer Biol Ther. 2013;14(2):100–7. doi:10.4161/cbt.22954.CrossRefPubMedPubMedCentralGoogle Scholar
Zaanan A, Park JM, Tougeron D, Huang S, Wu TT, Foster NR, et al. Association of beclin 1 expression with response to neoadjuvant chemoradiation therapy in patients with locally advanced rectal carcinoma. Int J Cancer. 2015;137(6):1498–502. doi:10.1002/ijc.29496.CrossRefPubMedPubMedCentralGoogle Scholar
Ogier-Denis E, Pattingre S, El Benna J, Codogno P. Erk1/2-dependent phosphorylation of Galpha-interacting protein stimulates its GTPase accelerating activity and autophagy in human colon cancer cells. J Biol Chem. 2000;275(50):39090–5. doi:10.1074/jbc.M006198200.CrossRefPubMedGoogle Scholar
Klingbeil P, Marhaba R, Jung T, Kirmse R, Ludwig T, Zoller M. CD44 variant isoforms promote metastasis formation by a tumor cell-matrix cross-talk that supports adhesion and apoptosis resistance. Mol Cancer Res. 2009;7(2):168–79. doi:10.1158/1541-7786.MCR-08-0207.CrossRefPubMedGoogle Scholar