TY - JOUR
T1 - Targeted Axl inhibition primes chronic lymphocytic leukemia B cells to apoptosis and shows synergistic/additive effects in combination with BTK inhibitors
AU - Sinha, Sutapa
AU - Boysen, Justin
AU - Nelson, Michael
AU - Secreto, Charla
AU - Warner, Steven L.
AU - Bearss, David J.
AU - Lesnick, Connie
AU - Shanafelt, Tait D.
AU - Kay, Neil E.
AU - Ghosh, Asish K.
N1 - Publisher Copyright:
© 2015 American Association for Cancer Research.
PY - 2015/5/1
Y1 - 2015/5/1
N2 - Purpose: B-cell chronic lymphocytic leukemia (CLL) is an incurable disease despite aggressive therapeutic approaches. We previously found that Axl receptor tyrosine kinase (RTK) plays a critical role in CLL B-cell survival. Here, we explored the possibility of using a high-affinity Axl inhibitor as a single agent or in combination with Bruton's tyrosine kinase (BTK) inhibitors for future clinical trial to treat patients with CLL. Experimental Design: Expression/activation status of other members of the TAM (e.g., Tyro3, Axl, and MER) family of RTKs in CLL B cells was evaluated. Cells were treated with a high-affinity orally bioavailable Axl inhibitor TP-0903 with or without the presence of CLL bone marrow stromal cells (BMSCs). Inhibitory effects of TP-0903 on the Axl signaling pathway were also evaluated in CLL B cells. Finally, cells were exposed to TP-0903 in combination with BTK inhibitors to determine any synergistic/additive effects of the combination. Results: CLL B cells overexpress Tyro3, but not MER. Of interest, Tyro3 remains as constitutively phosphorylated and forms a complex with Axl in CLL B cells. TP-0903 induces massive apoptosis in CLL B cells with LD50 values of nanomolar ranges. Importantly, CLL BMSCs could not protect the leukemic B cells from TP-0903-induced apoptosis. A marked reduction of the antiapoptotic proteins Mcl-1, Bcl-2, and XIAP and upregulation of the proapoptotic protein BIM in CLL B cells was detected as a result of Axl inhibition. Finally, combination of TP-0903 with BTK inhibitors augments CLL B-cell apoptosis. Conclusions: Administration of TP-0903 either as a single agent or in combination with BTK inhibitors may be effective in treating patients with CLL.
AB - Purpose: B-cell chronic lymphocytic leukemia (CLL) is an incurable disease despite aggressive therapeutic approaches. We previously found that Axl receptor tyrosine kinase (RTK) plays a critical role in CLL B-cell survival. Here, we explored the possibility of using a high-affinity Axl inhibitor as a single agent or in combination with Bruton's tyrosine kinase (BTK) inhibitors for future clinical trial to treat patients with CLL. Experimental Design: Expression/activation status of other members of the TAM (e.g., Tyro3, Axl, and MER) family of RTKs in CLL B cells was evaluated. Cells were treated with a high-affinity orally bioavailable Axl inhibitor TP-0903 with or without the presence of CLL bone marrow stromal cells (BMSCs). Inhibitory effects of TP-0903 on the Axl signaling pathway were also evaluated in CLL B cells. Finally, cells were exposed to TP-0903 in combination with BTK inhibitors to determine any synergistic/additive effects of the combination. Results: CLL B cells overexpress Tyro3, but not MER. Of interest, Tyro3 remains as constitutively phosphorylated and forms a complex with Axl in CLL B cells. TP-0903 induces massive apoptosis in CLL B cells with LD50 values of nanomolar ranges. Importantly, CLL BMSCs could not protect the leukemic B cells from TP-0903-induced apoptosis. A marked reduction of the antiapoptotic proteins Mcl-1, Bcl-2, and XIAP and upregulation of the proapoptotic protein BIM in CLL B cells was detected as a result of Axl inhibition. Finally, combination of TP-0903 with BTK inhibitors augments CLL B-cell apoptosis. Conclusions: Administration of TP-0903 either as a single agent or in combination with BTK inhibitors may be effective in treating patients with CLL.
UR - http://www.scopus.com/inward/record.url?scp=84941945167&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84941945167&partnerID=8YFLogxK
U2 - 10.1158/1078-0432.CCR-14-1892
DO - 10.1158/1078-0432.CCR-14-1892
M3 - Article
C2 - 25673699
AN - SCOPUS:84941945167
SN - 1078-0432
VL - 21
SP - 2115
EP - 2126
JO - Clinical Cancer Research
JF - Clinical Cancer Research
IS - 9
ER -