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Downregulation of IGFBP2 is associated with resistance to IGF1R therapy in rhabdomyosarcoma.

ABSTRACT: Agents targeting the insulin-like growth factor-1 receptor (IGF1R) are in clinical development, but, despite some initial success of single agents in sarcoma, response rates are low with brief durations. Thus, it is important to identify markers predictive of response, to understand mechanisms of resistance, and to explore combination therapies. In this study, we found that, although associated with PAX3-FKHR translocation, increased IGF1R level is an independent prognostic marker for worse overall survival, particularly in patients with PAX3-FKHR-positive rhabdomyosarcoma (RMS). IGF1R antibody-resistant RMS cells were generated using an in vivo model. Expression analysis indicated that IGFBP2 is both the most affected gene in the insulin-like growth factor (IGF) signaling pathway and the most significantly downregulated gene in the resistant lines, indicating that there is a strong selection to repress IGFBP2 expression in tumor cells resistant to IGF1R antibody. IGFBP2 is inhibitory to IGF1R phosphorylation and its signaling. Similar to antibodies to IGF1/2 or IGF2, the addition of exogenous IGFBP2 potentiates the activity of IGF1R antibody against the RMS cells, and it reverses the resistance to IGF1R antibody. In contrast to IGF1R, lower expression of IGFBP2 is associated with poorer overall survival, consistent with its inhibitory activity found in this study. Finally, blocking downstream Protein kinase B (AKT) activation with Phosphatidylinositide 3-kinases (PI3K)- or mammalian target of rapamycin (mTOR)-specific inhibitors significantly sensitized the resistant cells to the IGF1R antibody. These findings show that constitutive IGFBP2 downregulation may represent a novel mechanism for acquired resistance to IGF1R therapeutic antibody in vivo and suggest various drug combinations to enhance antibody activity and to overcome resistance.

SUBMITTER: Kang Z

PROVIDER: S-EPMC7667493 | biostudies-literature | 2014 Dec

REPOSITORIES: biostudies-literature

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Downregulation of IGFBP2 is associated with resistance to IGF1R therapy in rhabdomyosarcoma.

Kang Z Z Yu Y Y Zhu Y J YJ Davis S S Walker R R Meltzer P S PS Helman L J LJ Cao L L

Oncogene 20131202 50

Agents targeting the insulin-like growth factor-1 receptor (IGF1R) are in clinical development, but, despite some initial success of single agents in sarcoma, response rates are low with brief durations. Thus, it is important to identify markers predictive of response, to understand mechanisms of resistance, and to explore combination therapies. In this study, we found that, although associated with PAX3-FKHR translocation, increased IGF1R level is an independent prognostic marker for worse over ...[more]

PMID: 24292683

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Project description:Rhabdomyosarcoma (RMS) is the most common childhood sarcoma and is identified as either the embryonal or alveolar (ARMS) subtype. In approximately 75% of cases, ARMSs are characterized by specific chromosomal translocations that involve PAX and FKHR genes. ARMS gene expression signatures vary, depending on the presence or absence of the translocations. Insulin-like growth factor-binding protein 2 (IGFBP2) is strongly overexpressed in translocation-negative RMS. Because IGFBP2 is associated with tumorigenesis, we investigated its functional role in RMS. An analysis of IGFBP2 distribution in RMS cell lines revealed a strong accumulation in the Golgi complex, in which morphological characteristics appeared peculiarly modified. After silencing IGFBP2 expression, our microarray analysis revealed mostly cell cycle and actin cytoskeleton gene modulations. In parallel, IGFBP2-silenced cells showed reduced cell cycle and rates of invasion and decreased seeding in the lungs after tail vein injections in immunodeficient mice. An analysis of IGFBP2 mRNA and protein localization in human tumors showed abnormal protein accumulation in the Golgi complex, mostly in PAX/FKHR-negative RMS. Moreover, an analysis of patients with RMS revealed the presence of conspicuous circulating levels of IGFBP2 proteins in children with highly aggressive RMS tumors. Taken together, our data provide evidence that IGFBP2 contributes to tumor progression and that it could be used as a marker to better classify clinical and biological risks in RMS. Three independent silencing experiments on RH36, an embryonal rhabdomyosarcoma cell line, were performed to study the role of IGFBP2 oncogene in this childhood tumor. Each of 3 biological replicates has its own control which is represented by cell culture treated with a non-targeting siRNA (siCONTROL). 3 controls were used to produce a M-bM-^@M-^\control poolM-bM-^@M-^] that has been used as reference in all microarray experiments. Each microarray experiment consists of a competitive hybridization between test and reference RNA (e.g. silenced cells vs. control), labelled with Cy3 or Cy5. Two microarray experiments were performed for each of three silencing experiment (technical replicate). Each slide was scanned and the data was normalized and analyzed.

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Downregulation of IGFBP2 is associated with resistance to IGF1R therapy in rhabdomyosarcoma.

Publications

Downregulation of IGFBP2 is associated with resistance to IGF1R therapy in rhabdomyosarcoma.

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