Investigation of tumourigenic and metastasising CD44 properties in vitro and in vivo
Final Report Abstract
Osteosarcoma is the most common type of pediatric bone tumor. Despite great advances in chemotherapy during the past decades, the survival rates of osteosarcoma patients remain unsatisfactory. Drug resistance and formation of metastases are the main reasons, leading to treatment failure and poor prognosis. Merlin is a versatile tumor suppressor protein, encoded by neurofibromatosis type 2 (NF2) gene, implicated in osteosarcoma. Several lines of evidence suggest that Merlin exerts its tumor suppressor activity, at least in part, by forming an inhibitory complex with adhesion molecule CD44. Consistently, numerous NF2 mutations in cancer patients are predicted to perturb the interaction of Merlin with CD44. We hypothesized that disruption of the Merlin-CD44 complex through loss of Merlin, unleashes putative tumor- or metastasis-promoting functions of CD44. In this study we evaluated the role of CD44 in tumor development, progression and chemoresistance using Nf2-mutant mice as a model for metastatic osteosarcoma. To dissect the molecular alterations induced by deletion of Cd44, RNA sequencing was performed on Cd44-positive and Cd44-negative primary osteosarcoma tissues isolated from Nf2-mutant mice. Moreover, osteosarcoma cells were isolated from Nf2-mutant mice and subjected to extensive molecular and functional assays to investigate CD44- dependent processes. Our results demonstrate that the absence of the Cd44 gene has no effect on the frequency of primary osteosarcoma development, but it strongly diminishes osteosarcoma metastasis formation in the heterozygous Nf2-mutant mice. CD44 facilitates transendothelial migration of osteosarcoma cells, by upregulating levels of integrin β1. The passage through the endothelial cells appears to be critical in vivo, as CD44 significantly promoted formation of lung metastasis upon intravenous injection of osteosarcoma cells into immunocompromised mice. Our results also indicate that CD44 increases the resistance of osteosarcoma cells to doxorubicin by up-regulating the levels of multidrug resistance (MDR) 1 protein expression. Moreover, high throughput sequencing analysis identified differential regulation of several apoptosis-related genes in Cd44-positive and Cd44-negative primary osteosarcomas, including p53 apoptosis effector related to PMP-22 (Perp). Deletion of Cd44 in osteosarcoma cells led to doxorubicin-dependent p53 activation and a profound increase in Perp mRNA expression. Overall, our results suggest that CD44 contributes to drug resistance and promotes metastasis formation of osteosarcoma. Thus targeting CD44 may sensitize osteosarcoma to standard chemotherapy and inhibit metastatic spreading of osteosarcoma.
Publications
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Cluster of differentiation 44 promotes osteosarcoma progression in mice lacking the tumor suppressor Merlin. International Journal of Cancer, 147(9), 2564-2577.
Ma, Junzhi; Klemm, Janina; Gerardo‐Ramírez, Monserrat; Frappart, Lucien; Castven, Darko; Becker, Diana; Zoch, Ansgar; Parent, Romain; Bartosch, Birke; Minnich, Kerstin; Giovannini, Marco; Danckwardt, Sven; Hartmann, Nils; Morrison, Helen; Herrlich, Peter; Marquardt, Jens U. & Hartmann, Monika
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CD44 Contributes to the Regulation of MDR1 Protein and Doxorubicin Chemoresistance in Osteosarcoma. International Journal of Molecular Sciences, 23(15), 8616.
Gerardo-Ramírez, Monserrat; Keggenhoff, Friederike L.; Giam, Vanessa; Becker, Diana; Groth, Marco; Hartmann, Nils; Straub, Beate K.; Morrison, Helen; Galle, Peter R.; Marquardt, Jens U.; Herrlich, Peter & Hartmann, Monika
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Deletion of Cd44 Inhibits Metastasis Formation of Liver Cancer in Nf2-Mutant Mice. Cells, 12(9), 1257.
Gerardo-Ramírez, Monserrat; Giam, Vanessa; Becker, Diana; Groth, Marco; Hartmann, Nils; Morrison, Helen; May-Simera, Helen L.; Radsak, Markus P.; Marquardt, Jens U.; Galle, Peter R.; Herrlich, Peter; Straub, Beate K. & Hartmann, Monika
