Neurotrophin receptors expression and JNK pathway activation in human astrocytomas

<p>Abstract</p> <p>Background</p> <p>Neurotrophins are growth factors that regulate cell growth, differentiation and apoptosis in the nervous system. Their diverse actions are mediated through two different transmembrane – receptor signaling systems: Trk receptor tyrosine kinases (TrkA, TrkB, TrkC) and p75^NTRneurotrophin receptor. Trk receptors promote cell survival and differentiation while p75^NTRinduces, in most cases, the activity of JNK-p53-Bax apoptosis pathway or suppresses intracellular survival signaling cascades. Robust Trk activation blocks p75^NTR-induced apoptosis by suppressing the JNK-p53-Bax pathway. The aim of this exploratory study was to investigate the expression levels of neurotrophin receptors, Trks and p75^NTR, and the activation of JNK pathway in human astrocytomas and in adjacent non-neoplastic brain tissue.</p> <p>Methods</p> <p>Formalin-fixed paraffin-embedded serial sections from 33 supratentorial astrocytomas (5 diffuse fibrillary astrocytomas, WHO grade II; 6 anaplastic astrocytomas, WHO grade III; 22 glioblastomas multiforme, WHO grade IV) were immunostained following microwave pretreatment. Polyclonal antibodies against TrkA, TrkB, TrkC and monoclonal antibodies against p75^NTRand phosphorylated forms of JNK (pJNK) and c-Jun (pc-Jun) were used. The labeling index (LI), defined as the percentage of positive (labeled) cells out of the total number of tumor cells counted, was determined.</p> <p>Results</p> <p>Moderate to strong, granular cytoplasmic immunoreactivity for TrkA, TrkB and TrkC receptors was detected in greater than or equal to 10% of tumor cells in the majority of tumors independently of grade; on the contrary, p75^NTRreceptor expression was found in a small percentage of tumor cells (~1%) in some tumors. The endothelium of tumor capillaries showed conspicuous immunoreactivity for TrkB receptor. Trk immunoreactivity seemed to be localized in some neurons and astrocytes in non-neoplastic tissue. Phosphorylated forms of JNK (pJNK) and c-Jun (pc-Jun) were significantly co-expressed in a tumor grade-dependent manner (p < 0.05). Interestingly, a statistically significant (p < 0.05) reverse relationship between Trk receptors LIs and pc-Jun/pJNK LIs was noted in some glioblastomas multiforme.</p> <p>Conclusion</p> <p>In the context of astrocytomas, Trk receptors (TrkA, TrkB, TrkC) expression may promote tumor growth independently of grade. Furthermore, activation of JNK pathway may contribute to progression towards malignancy. Considering the fact that regional tumor heterogeneity may be a limiting factor for immunohistochemical studies, the significance of the reverse relationship between Trk receptors and pc-Jun/pJNK LIs with respect to biological behavior of human astrocytomas requires further evaluation.</p

Survivin overexpression in HCC and liver cirrhosis differentially correlates with p-STAT3 and E-cadherin

Survivin, a member of the family of inhibitorof apoptosis proteins, functions as a key regulator ofapoptosis and cell proliferation. Overexpression ofsurvivin has been implicated in several human cancers,including human hepatocellular carcinoma (HCC).Although several factors have been shown in vitrotoupregulate survivin expression in cancer cells, the invivoregulators of survivin in human hepato-carcinogenesis are largely unknown. We studied byimmunohistochemistry the protein expression ofsurvivin in relation to cyclin D1, phosphorylated signaltransducer and activator of transcription 3 (p-STAT3), ß-catenin, E-cadherin and phosphorylated-Akt (p-Akt) in69 cases of HCC and adjacent liver cirrhosis. Survivinwas expressed in 63/69 (91.3%) cases of HCC and in40/47 (85.1%) cases of liver cirrhosis. Survivinlocalization in HCC was exclusively nuclear, whileintense cytoplasmic and low nuclear expression ofsurvivin was observed in cases of cirrhosis. Survivinexpression in HCC correlated significantly with lowgrade tumors, expression of cyclin D1 and p-STAT3.Expression of survivin in liver cirrhosis correlated withdownregulation of E-cadherin expression. There was nosignificant correlation of survivin with ß-catenin or p-Akt in HCC or liver cirrhosis. In conclusion, we showedan association of nuclear survivin with welldifferentiated HCC, as well as with the expression of thecell cycle regulator cyclin D1. Activation of STAT3 andloss of E-cadherin but not ß-catenin or Akt pathwaysseem to be implicated in survivin upregulation in HCCand liver cirrhosis

Strong TrkA granular cytoplasmic immunostaining in giant cells of glioblastoma multiforme (grade IV), ×400

<p><b>Copyright information:</b></p><p>Taken from "Neurotrophin receptors expression and JNK pathway activation in human astrocytomas"</p><p>http://www.biomedcentral.com/1471-2407/7/202</p><p>BMC Cancer 2007;7():202-202.</p><p>Published online 31 Oct 2007</p><p>PMCID:PMC2180182.</p><p></p

Grade IV tumor (glioblastoma multiforme) exhibiting strong nuclear (arrows) and cytoplasmic immunostaining of pJNK and strong cytoplasmic immunostaining of TrkB (b) and TrkC (c) neurotrophin receptors, ×400

<p><b>Copyright information:</b></p><p>Taken from "Neurotrophin receptors expression and JNK pathway activation in human astrocytomas"</p><p>http://www.biomedcentral.com/1471-2407/7/202</p><p>BMC Cancer 2007;7():202-202.</p><p>Published online 31 Oct 2007</p><p>PMCID:PMC2180182.</p><p></p