A positive feedback loop involving the Wnt/β-catenin/MYC/Sox2 axis defines a highly tumorigenic cell subpopulation in ALK-positive anaplastic large cell lymphoma.
We have previously described the existence of two phenotypically distinct cell subsets in ALK-positive anaplastic large cell lymphoma (ALK + ALCL) based on their differential responsiveness to a Sox2 reporter (SRR2), with reporter-responsive (RR) cells being more tumorigenic and chemoresistant than reporter-unresponsive (RU) cells. However, the regulator(s) of RU/RR dichotomy are not identified. In this study, we aim to delineate the key regulator(s) of RU/RR dichotomy.



JASPER motif match analysis was used to identify the putative factors binding to SRR2 sequence. SRR2 probe pull-down assay and quantitate real-time PCR were performed to analyze the regulation of Sox2 transcriptional activity by MYC. Methylcellulose colony formation assay, chemoresistance to doxorubicin and mouse xenograft study were performed to investigate the biological functions of MYC. PCR array and western blotting were executed to study related signaling pathways that regulate MYC expression. Immunofluorescence and immunohistochemistry assay were initiated to evaluate the expression of MYC and its correlation with its regulator by chi-square test analysis in human primary tumor cells.



We identified MYC as a potential regulator of RU/RR dichotomy. In support of its role, MYC was highly expressed in RR cells compared to RU cells, and inhibition of MYC substantially decreased the Sox2/SRR2 binding, Sox2 transcriptional activity, chemoresistance, and methylcellulose colony formation. In contrast, enforced expression of MYC in RU cells conferred the RR phenotype. The Wnt/β-catenin pathway, a positive regulator of MYC, was highly active in RR but not RU cells. While inhibition of this pathway in RR cells substantially decreased MYC expression and SRR2 reporter activity, experimental activation of this pathway led to the opposite effects in RU cells. Collectively, our results support a model in which a positive feedback loop involving Wnt/β-catenin/MYC and Sox2 contributes to the RR phenotype. In a mouse xenograft model, RU cells stably transfected with MYC showed upregulation of the Wnt/β-catenin/MYC/Sox2 axis and increased tumorigenecity. Correlating with these findings, there was a significant correlation between the expression of active β-catenin and MYC in ALK + ALCL primary tumor cells.



A positive feedback loop involving the Wnt/β-catenin/MYC/Sox2 axis defines a highly tumorigenic cell subset in ALK + ALCL.
Department of Laboratory Medicine and Pathology, 5142J Katz Group Centre for Pharmacy and Health Research, University of Alberta, Edmonton, Alberta, T6G 1Z2, Canada.
Chengsheng
C
Wu
Department of Laboratory Medicine and Pathology, 5142J Katz Group Centre for Pharmacy and Health Research, University of Alberta, Edmonton, Alberta, T6G 1Z2, Canada.|Department of Biochemistry and Molecular Biology, Shantou University Medical College, Shantou, China.
Hai-Feng
HF
Zhang
Department of Laboratory Medicine and Pathology, 5142J Katz Group Centre for Pharmacy and Health Research, University of Alberta, Edmonton, Alberta, T6G 1Z2, Canada.
Nidhi
N
Gupta
Department of Laboratory Medicine and Pathology, 5142J Katz Group Centre for Pharmacy and Health Research, University of Alberta, Edmonton, Alberta, T6G 1Z2, Canada.
Abdulraheem
A
Alshareef
Department of Laboratory Medicine and Pathology, 5142J Katz Group Centre for Pharmacy and Health Research, University of Alberta, Edmonton, Alberta, T6G 1Z2, Canada.
Qian
Q
Wang
Department of Laboratory Medicine and Pathology, 5142J Katz Group Centre for Pharmacy and Health Research, University of Alberta, Edmonton, Alberta, T6G 1Z2, Canada.
Yung-Hsing
YH
Huang
Department of Surgery, University of Alberta, Edmonton, Alberta, Canada.
Jamie T
JT
Lewis
Department of Surgery, University of Alberta, Edmonton, Alberta, Canada.
Donna N
DN
Douglas
Department of Surgery, University of Alberta, Edmonton, Alberta, Canada.
Norman M
NM
Kneteman
Department of Laboratory Medicine and Pathology, 5142J Katz Group Centre for Pharmacy and Health Research, University of Alberta, Edmonton, Alberta, T6G 1Z2, Canada. rlai@ualberta.ca.|Department of Oncology, University of Alberta, Edmonton, Alberta, Canada. rlai@ualberta.ca.|DynaLIFEDX Medical Laboratories, Edmonton, Alberta, Canada. rlai@ualberta.ca.
Raymond
R
Lai
D000077548:Anaplastic Lymphoma Kinase; D000818:Animals; D063646:Carcinogenesis; D025461:Feedback, Physiological; D015972:Gene Expression Regulation, Neoplastic; D064593:Heterografts; D006801:Humans; D017728:Lymphoma, Large-Cell, Anaplastic / Q000378:metabolism* / Q000473:pathology*; D051379:Mice; D016271:Proto-Oncogene Proteins c-myc / Q000032:analysis / Q000378:metabolism / Q000502:physiology; D020794:Receptor Protein-Tyrosine Kinases; D055748:SOXB1 Transcription Factors / Q000378:metabolism; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D060449:Wnt Signaling Pathway / Q000502:physiology*; D051176:beta Catenin / Q000378:metabolism
C489427:MYC protein, human; D016271:Proto-Oncogene Proteins c-myc; C527782:SOX2 protein, human; D055748:SOXB1 Transcription Factors; D051176:beta Catenin; C000626173:ALK protein, human; C000626174:Alk protein, mouse; D000077548:Anaplastic Lymphoma Kinase; D020794:Receptor Protein-Tyrosine Kinases
ALK-positive anaplastic large cell lymphoma; Cancer stemness; Intra-tumoral heterogeneity; MYC; Sox2; Wnt/β-catenin