title: Insulin growth factor-2 binding protein 3 (IGF2BP3) is a glioblastoma-specific marker that activates phosphatidylinositol 3-kinase/mitogen-activated protein kinase (PI3K/MAPK) pathways by modulating IGF-2.
abstract: Glioblastoma is the most common and malignant form of primary astrocytoma. Upon investigation of the insulin-like growth factor (IGF) pathway, we found the IGF2BP3/IMP3 transcript and protein to be up-regulated in GBMs but not in lower grade astrocytomas (p < 0.0001). IMP3 is an RNA binding protein known to bind to the 5'-untranslated region of IGF-2 mRNA, thereby activating its translation. Overexpression- and knockdown-based studies establish a role for IMP3 in promoting proliferation, anchorage-independent growth, invasion, and chemoresistance. IMP3 overexpressing B16F10 cells also showed increased tumor growth, angiogenesis, and metastasis, resulting in poor survival in a mouse model. Additionally, the infiltrating front, perivascular, and subpial regions in a majority of the GBMs stained positive for IMP3. Furthermore, two different murine glioma models were used to substantiate the above findings. In agreement with the translation activation functions of IMP3, we also found increased IGF-2 protein in the GBM tumor samples without a corresponding increase in its transcript levels. Also, in vitro IMP3 overexpression/knockdown modulated the IGF-2 protein levels without altering its transcript levels. Additionally, IGF-2 neutralization and supplementation studies established that the proproliferative effects of IMP3 were indeed mediated through IGF-2. Concordantly, PI3K and MAPK, the downstream effectors of IGF-2, are activated by IMP3 and are found to be essential for IMP3-induced cell proliferation. Thus, we have identified IMP3 as a GBM-specific proproliferative and proinvasive marker acting through IGF-2 resulting in the activation of oncogenic PI3K and MAPK pathways.
authors: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560 012, India.
authors: Ramaswamy
authors: R
authors: Suvasini
authors: Bhargava
authors: B
authors: Shruti
authors: Balaram
authors: B
authors: Thota
authors: Sridevi Vijay
authors: SV
authors: Shinde
authors: Dinorah
authors: D
authors: Friedmann-Morvinski
authors: Zahid
authors: Z
authors: Nawaz
authors: Krishnarao Venkatesh
authors: KV
authors: Prasanna
authors: Kandavel
authors: K
authors: Thennarasu
authors: Alangar Sathyaranjandas
authors: AS
authors: Hegde
authors: Arimappamagan
authors: A
authors: Arivazhagan
authors: Bangalore Ashwathnarayanarao
authors: BA
authors: Chandramouli
authors: Vani
authors: V
authors: Santosh
authors: Kumaravel
authors: K
authors: Somasundaram
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