CD44 Expression Level and Isoform Contributes to Pancreatic Cancer Cell Plasticity, Invasiveness, and Response to Therapy.
OBJECTIVE
A subpopulation of pancreatic ductal adenocarcinoma (PDAC) cells is thought to be inherently resistant to chemotherapy or to give rise to tumor cells that become resistant during treatment. Here we determined the role of CD44 expression and its isoforms as a marker and potential target for tumor cells that give rise to invasive and gemcitabine-resistant tumors.


METHODS
RT-PCR, Western blotting, and DNA sequencing was used to determine CD44 isoform and expression levels. Flow cytometry was used to sort cells on the basis of their CD44 expression level. CD44 expression was knocked down using shRNA. Tumorigenic properties were determined by clonogenic and Matrigel assays, IHC, tumor growth in vivo using luciferase imaging and by tumor weight.


RESULTS
We identified an invasive cell population that gives rise to gemcitabine-resistant tumors. These cancer cells express a high level of CD44 standard isoform and have an EMT phenotype (CD44s/EMT). In vivo, CD44s/EMT engraft and expand rapidly and give rise to tumors that express high levels of CD44 isoforms that contain multiple exon variants. CD44low-expressing cells show continued sensitivity to gemcitabine in vivo and knockdown of CD44 in CD44s/EMT cells increases sensitivity to gemcitabine and decreases invasiveness.


CONCLUSIONS
PDAC cells expressing high levels of CD44s with a mesenchymal-like phenotype were highly invasive and developed gemcitabine resistance in vivo Thus, initial targeting CD44 or reversing the CD44highphenotype may improve therapeutic response. Clin Cancer Res; 22(22); 5592-604. ©2016 AACR.
Department of Medicine, Division of Medical Oncology, University of Texas Health Science Center at San Antonio, San Antonio, Texas.
Shujie
S
Zhao
Department of Medicine, Division of Medical Oncology, University of Texas Health Science Center at San Antonio, San Antonio, Texas.
Chen
C
Chen
Department of Medicine, Division of Medical Oncology, University of Texas Health Science Center at San Antonio, San Antonio, Texas.|Experimental and Developmental Therapeutics Program, Cancer Therapy and Research Center, San Antonio, Texas.
Katherine
K
Chang
Department of Medicine, Division of Medical Oncology, University of Texas Health Science Center at San Antonio, San Antonio, Texas.|Experimental and Developmental Therapeutics Program, Cancer Therapy and Research Center, San Antonio, Texas.
Anand
A
Karnad
Department of Pathology, University of Texas Health Science Center at San Antonio, San Antonio, Texas.
Jaishree
J
Jagirdar
Department of Urology, University of Texas Health Science Center at San Antonio, San Antonio, Texas.|Research and Development, Audie Murphy Veterans Administration Hospital, San Antonio, Texas.
Addanki P
AP
Kumar
Department of Medicine, Division of Medical Oncology, University of Texas Health Science Center at San Antonio, San Antonio, Texas. freemanjw@uthscsa.edu.|Experimental and Developmental Therapeutics Program, Cancer Therapy and Research Center, San Antonio, Texas.|Research and Development, Audie Murphy Veterans Administration Hospital, San Antonio, Texas.
James W
JW
Freeman
D021441:Carcinoma, Pancreatic Ductal / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology*; D003841:Deoxycytidine / Q000031:analogs & derivatives / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000502:physiology; D006801:Humans; D018960:Hyaluronan Receptors / Q000378:metabolism*; D010190:Pancreatic Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology*; D020033:Protein Isoforms / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D000093542:Gemcitabine
C497483:CD44 protein, human; D018960:Hyaluronan Receptors; D020033:Protein Isoforms; D034741:RNA, Small Interfering; D003841:Deoxycytidine; D000093542:Gemcitabine