The Influence of Hyaluronan-CD44 Interaction on Topoisomerase II Activity and Etoposide Cytotoxicity in Head and Neck Cancer

Abstract

Objective: To investigate the downstream molecular targets of hyaluronan (HA)-CD44 and phospholipase C (PLC)-mediated calcium ion (Ca 2ϩ ) signaling in head and neck squamous cell carcinoma (HNSCC). Hyaluronan is a ligand for the CD44 receptor, which interacts with multiple signaling pathways to influence cellular behavior. We recently determined that HA-CD44 interaction promotes PLC-mediated Ca 2ϩ signaling and cisplatin resistance in HNSCC.Design: Proliferation of HNSCC tumor cells and topoisomerase (Topo) II enzymatic activity, including DNAcleavable complex formation and DNA decatenation, were analyzed in the presence or absence of HA, the Topo II poison etoposide (VP-16), and various inhibitors of PLC and Ca 2ϩ -calmodulin kinase II (CaMKII) signaling.Results: Treatment with HA promoted Topo II phosphorylation, suggesting that HA can modulate Topo II activity. Topoisomerase II-mediated DNA cleavable com-plex formation was increased by VP-16, and this increase was significantly enhanced by noncytotoxic doses of the PLC inhibitor U73122 and the CaMKII inhibitor KN-62, implicating PLC and CaMKII in Topo II regulation. However, the drug-and inhibitor-mediated increase in DNA cleavable complex formation was reduced with HA pretreatment. Inhibitors of PLC and CaMKII also enhanced VP-16 inhibition of Topo II-mediated DNA decatenation. Treatment with HA reduced VP-16 cytotoxic activity. On the other hand, U73122 and KN-62 enhanced VP-16 cytotoxic activity and reduced the ability of HA to promote VP-16 resistance. Conclusion:Our results suggest that HA, PLC, and CaMKII are upstream regulators of Topo II-mediated DNA metabolism in HNSCC and that this signaling pathway could be a promising target for the development of novel therapies against HNSCC.

Role of Hyaluronan-Mediated CD44 Signaling in Head and Neck Squamous Cell Carcinoma Progression and Chemoresistance

“…RhoA/Ca 2ϩ Signaling-Regulated Chemoresistance HA/CD44 interaction has been shown to promote resistance to multiple chemotherapeutic agents in HNSCC, including cisplatin, methotrexate, doxorubicin (Adriamycin), and etoposide. 38,40,49 Several cell signaling mechanisms appear to promote CD44-mediated chemoresistance in HNSCC, including EGFR-related signaling pathways (as already described here). 38 Recent work by our groupsuggests that regulation of Ca 2ϩ may also affect chemoresistance (unpublished data).…”

Reduction of Hyaluronan-CD44–Mediated Growth, Migration, and Cisplatin Resistance in Head and Neck Cancer Due to Inhibition of Rho Kinase and PI-3 Kinase Signaling

“…In addition, HA and CD44 have been linked to chemotherapy resistance in several tumor models. We previously reported expression of CD44 in a panel of HNSCC cell lines and demonstrated that HA-CD44 signaling promotes tumor progression behaviors in several HNSCC cell lines, including HSC-3, HOC313, SCC-4, and MDA1483 4–7,10. In the present investigation, we studied HA-CD44 interaction to upregulate Rho kinase– and PI-3 kinase–mediated signaling pathways, thereby contributing to tumor progression.…”

“…Interaction of HA and CD44 with various signaling pathways is being increasingly examined as a possible mechanism mediating chemoresistance. A previous report from our group indicated that HA-CD44 interaction with EGFR signaling and phospholipase C-mediated Ca 2+ signaling promoted resistance to cisplatin, methotrexate, and adriamycin in HNSCC 4,5,7. There are likely multiple downstream signaling pathways through which HA-CD44—mediated chemoresistance occurs.…”

CD44 induced enhancement of phosphatase activity and calcium influx: Modifications of EGR-1 expression and cell proliferation

“…To determine if E6.1 Jurkat cells were utilizing Ca 2+ release activated calcium channels (CRAC) for their calcium influx we cultured cells with the inhibitor, Ni 2+ [20] , [21] , [22] . While both CD44 expressing and vector control E6.1 Jurkat cells were both inhibited by Ni 2+ the vector control cells proliferated twice as much as the CD44 expressing cells.…”