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Originally published online as doi:10.2353/ajpath.2009.080982 on July 16, 2009

Published online before print July 16, 2009
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(American Journal of Pathology. 2009;175:825-834.)
© 2009 American Society for Investigative Pathology
DOI: 10.2353/ajpath.2009.080982

IL-21 Contributes to JAK3/STAT3 Activation and Promotes Cell Growth in ALK-Positive Anaplastic Large Cell Lymphoma

Jennifer Dien Bard*, Pascal Gelebart*, Mona Anand*, Zoulika Zak*, Samar A. Hegazy*, Hesham M. Amin{dagger} and Raymond Lai*

From the Department of Laboratory Medicine and Pathology,* Cross Cancer Institute and University of Alberta, Edmonton, Canada; and the Department of Hematopathology,{dagger} the University of Texas M.D. Anderson Cancer Center, Houston, Texas

Interleukin (IL)-21 has been reported to both stimulate cell growth and promote survival in benign lymphoid cells and several types of hematopoietic neoplasms. It induces JAK3/STAT3 signaling, a biologically important cellular pathway activated in most cases of anaplastic lymphoma kinase (ALK)-expressing anaplastic large cell lymphoma (ALK+ALCL). Therefore, we hypothesize that IL-21 may contribute to JAK3/STAT3 activation and cell growth in ALK+ALCL. By reverse transcription-PCR, we found consistent expression of IL-21 receptor (IL-21R) in all ALK+ALCL cell lines and frozen tumors examined. IL-21 was also consistently expressed in ALK+ALCL tumors, although its mRNA was detectable in only one of three cell lines tested. By immunohistochemistry, we examined 10 paraffin-embedded ALK+ALCL tumors; all cases were positive for both IL-21 and IL-21R in these neoplastic cells. IL-21 signaling is biologically significant in ALK+ALCL since the addition of recombinant IL-21 enhanced the activation of JAK3/STAT3 and significantly increased cell growth in ALK+ALCL cell lines. However, small interfering RNA down-regulation of IL-21R significantly decreased both STAT3 activation and cell growth. IL-21R expression is not linked to nucleophosmin-ALK since forced expression of nucleophosmin-ALK and small interfering RNA down-regulation of nucleophosmin-ALK did not significantly change the expression of either IL-21R or IL-21. Our findings thus support the enhancement of JAK3/STAT3 activation and cell growth in ALK+ALCL via IL-21 signaling. These results further support the concept that constitutive activation of STAT3 in these tumors is multifactorial.




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[Abstract] [Full Text] [PDF]


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