TY - JOUR
T1 - ABCG2 is a direct transcriptional target of hedgehog signaling and involved in stroma-induced drug tolerance in diffuse large B-cell lymphoma
AU - Singh, R. R.
AU - Kunkalla, K.
AU - Qu, C.
AU - Schlette, E.
AU - Neelapu, S. S.
AU - Samaniego, F.
AU - Vega, F.
N1 - Funding Information:
We thank Dr Susan E Bates (NIH) for providing the ABCG2 promoter luciferase constructs. We also thank Professor Michael G Rosenblum, Department of Experimental Therapeutics, MD Anderson Cancer Center for providing OCI-LY3 and OCI-LY10 cell lines. The primary tumor samples were provided by the Hematopathology and Lymphoma Tissue Banks of the UT MD Anderson Cancer Center (supported by the NCI/NIH Grant CA16672). This research was supported by funds from The Translational Grant of The Leukemia and Lymphoma Society (to RRS and FV), K08 Physician-Scientist Award 1 K08 CA143151-01 (NIH) (to FV), SPORE Lymphoma Grant UT MD Anderson Cancer Center Lymphoma SPORE 1P50CA136411-01A1 (to FV) and Lauri Strauss Leukemia Foundation Grant award (to RRS and FV).
PY - 2011/12/8
Y1 - 2011/12/8
N2 - Successful treatment of diffuse large B-cell lymphoma (DLBCL) is frequently hindered by the development of resistance to conventional chemotherapy resulting in disease relapse and high mortality. High expression of antiapoptotic and/or drug transporter proteins induced by oncogenic signaling pathways has been implicated in the development of chemoresistance in cancer. Previously, our studies showed that high expression of adenosine triphosphate-binding cassette drug transporter ABCG2 in DLBCL correlated inversely with disease-and failure-free survival. In this study, we have implicated activated hedgehog (Hh) signaling pathway as a key factor behind high ABCG2 expression in DLBCL through direct upregulation of ABCG2 gene transcription. We have identified a single binding site for GLI transcription factors in the ABCG2 promoter and established its functionality using luciferase reporter, site-directed mutagenesis and chromatin-immunoprecipitation assays. Furthermore, in DLBCL tumor samples, significantly high ABCG2 and GLI1 levels were found in DLBCL tumors with lymph node involvement in comparison with DLBCL tumor cells collected from pleural and/or peritoneal effusions. This suggests a role for the stromal microenvironment in maintaining high levels of ABCG2 and GLI1. Accordingly, in vitro co-culture of DLBCL cells with HS-5 stromal cells increased ABCG2 mRNA and protein levels by paracrine activation of Hh signaling. In addition to ABCG2, co-culture of DLBCL cells with HS-5 cells also resulted in increase expression of the antiapoptotic proteins BCL2, BCL-xL and BCL2A1 and in induced chemotolerance to doxorubicin and methotrexate, drugs routinely used for the treatment of DLBCL. Similarly, activation of Hh signaling in DLBCL cell lines with recombinant Shh N-terminal peptide resulted in increased expression of BCL2 and ABCG2 associated with increased chemotolerance. Finally, functional inhibition of ABCG2 drug efflux activity with fumitremorgin C or inhibition of Hh signaling with cyclopamine-KAAD abrogated the stroma-induced chemotolerance suggesting that targeting ABCG2 and Hh signaling may have therapeutic value in overcoming chemoresistance in DLBCL.
AB - Successful treatment of diffuse large B-cell lymphoma (DLBCL) is frequently hindered by the development of resistance to conventional chemotherapy resulting in disease relapse and high mortality. High expression of antiapoptotic and/or drug transporter proteins induced by oncogenic signaling pathways has been implicated in the development of chemoresistance in cancer. Previously, our studies showed that high expression of adenosine triphosphate-binding cassette drug transporter ABCG2 in DLBCL correlated inversely with disease-and failure-free survival. In this study, we have implicated activated hedgehog (Hh) signaling pathway as a key factor behind high ABCG2 expression in DLBCL through direct upregulation of ABCG2 gene transcription. We have identified a single binding site for GLI transcription factors in the ABCG2 promoter and established its functionality using luciferase reporter, site-directed mutagenesis and chromatin-immunoprecipitation assays. Furthermore, in DLBCL tumor samples, significantly high ABCG2 and GLI1 levels were found in DLBCL tumors with lymph node involvement in comparison with DLBCL tumor cells collected from pleural and/or peritoneal effusions. This suggests a role for the stromal microenvironment in maintaining high levels of ABCG2 and GLI1. Accordingly, in vitro co-culture of DLBCL cells with HS-5 stromal cells increased ABCG2 mRNA and protein levels by paracrine activation of Hh signaling. In addition to ABCG2, co-culture of DLBCL cells with HS-5 cells also resulted in increase expression of the antiapoptotic proteins BCL2, BCL-xL and BCL2A1 and in induced chemotolerance to doxorubicin and methotrexate, drugs routinely used for the treatment of DLBCL. Similarly, activation of Hh signaling in DLBCL cell lines with recombinant Shh N-terminal peptide resulted in increased expression of BCL2 and ABCG2 associated with increased chemotolerance. Finally, functional inhibition of ABCG2 drug efflux activity with fumitremorgin C or inhibition of Hh signaling with cyclopamine-KAAD abrogated the stroma-induced chemotolerance suggesting that targeting ABCG2 and Hh signaling may have therapeutic value in overcoming chemoresistance in DLBCL.
KW - ABCG2
KW - ATP-binding cassettes
KW - GLI
KW - diffuse large B-cell lymphoma
KW - hedgehog pathway
UR - http://www.scopus.com/inward/record.url?scp=82955237344&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=82955237344&partnerID=8YFLogxK
U2 - 10.1038/onc.2011.195
DO - 10.1038/onc.2011.195
M3 - Article
C2 - 21625222
AN - SCOPUS:82955237344
SN - 0950-9232
VL - 30
SP - 4874
EP - 4886
JO - Oncogene
JF - Oncogene
IS - 49
ER -