Abstract
Despite significant advances in cancer treatment and management, more than 60% of patients with neuroblastoma present with very poor prognosis in the form of metastatic and aggressive disease. Solid tumors including neuroblastoma are thought to be heterogeneous with a sub-population of stem-like cells that are treatment-evasive with highly malignant characteristics. We previously identified a phenomenon of reversible adaptive plasticity (RAP) between anchorage dependent (AD) cells and anchorage independent (AI) tumorspheres in neuroblastoma cell cultures. To expand our molecular characterization of the AI tumorspheres, we sought to define the comprehensive proteomic profile of murine AD and AI neuroblastoma cells. The proteomic profiles of the two phenotypic cell populations were compared to each other to determine the differential protein expression and molecular pathways of interest. We report exclusive or significant up-regulation of tumorigenic pathways expressed by the AI tumorspheres compared to the AD cancer cells. These pathways govern metastatic potential, enhanced malignancy and epithelial to mesenchymal transition. Furthermore, radio-therapy induced significant up-regulation of specific tumorigenic and proliferative proteins, namely survivin, CDC2 and the enzyme Poly [ADP-ribose] polymerase 1. Bio-functional characteristics of the AI tumorspheres were resistant to sutent inhibition of receptor tyrosine kinases (RTKs) as well as to 2.5 Gy radio-therapy as assessed by cell survival, proliferation, apoptosis and migration. Interestingly, PDGF-BB stimulation of the PDGFRβ led to transactivation of EGFR and VEGFR in AI tumorspheres more potently than in AD cells. Sutent inhibition of PDGFRβ abrogated this transactivation in both cell types. In addition, 48 h sutent treatment significantly down-regulated the protein expression of PDGFRβ, MYCN, SOX2 and Survivin in the AI tumorspheres and inhibited tumorsphere self-renewal. Radio-sensitivity in AI tumorspheres was enhanced when sutent treatment was combined with survivin knock-down. We conclude that AI tumorspheres have a differential protein expression compared to AD cancer cells that contribute to their malignant phenotype and radio-resistance. Specific targeting of both cellular phenotypes is needed to improve outcomes in neuroblastoma patients.
Highlights
Despite continuous advancement in cancer therapy approaches, neuroblastoma (NB) recurrence with metastatic disease remains a major concern with poor prognostic outcomes [1]
Functional analysis of differentially expressed proteins indicated specific upregulation in proteins involved in small molecule biochemistry, RNA post translational modification, and energy metabolism in anchorage independent (AI) cells compared to anchorage dependent (AD) cells (Fig 1A)
Among the significantly-higher expressed proteins in the NB AI tumorspheres that we validated using Western blot analysis, was the Poly (ADP-ribose) polymerase 1 (PARP1), melanoma inhibitory activity 3 (MIA3), RhoA and hepatoma derived growth factor-related protein (HDGFR), which are associated with increased metastases, stemness, invasion and malignancy [9, 10, 11, 12]
Summary
Despite continuous advancement in cancer therapy approaches, neuroblastoma (NB) recurrence with metastatic disease remains a major concern with poor prognostic outcomes [1]. High-risk cases present with a very aggressive form of the disease with treatment-evasive properties and malignant recurrence that is usually fatal. It is considered that a sub-population of malignant, treatment-resistant cells reside within the bulk of many solid and hematologic tumors [3]. These cells do not undergo apoptosis with therapeutic intervention, but rather remain dormant for a period of time, ranging from months to years, after which they repopulate themselves giving rise to the original tumor with a highly aggressive phenotype and malignant properties including treatment-resistance [4]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
