ACVR1C/SMAD2 signaling promotes invasion and growth in retinoblastoma

Abstract

Retinoblastoma is the most common intraocular cancer in children. While the primary tumor can often be treated by local or systemic chemotherapy, metastatic dissemination is generally resistant to therapy and remains a leading cause of pediatric cancer death in much of the world. In order to identify new therapeutic targets in aggressive tumors, we sequenced RNA transcripts in five snap frozen retinoblastomas which invaded the optic nerve and five which did not. A three-fold increase was noted in mRNA levels of ACVR1C/ALK7, a type I receptor of the TGF-β family, in invasive retinoblastomas, while downregulation of DACT2 and LEFTY2, negative modulators of the ACVR1C signaling, was observed in most invasive tumors. A two- to three-fold increase in ACVR1C mRNA was also found in invasive WERI Rb1 and Y79 cells as compared to non-invasive cells in vitro. Transcripts of ACVR1C receptor and its ligands (Nodal, Activin A/B, and GDF3) were expressed in six retinoblastoma lines, and evidence of downstream SMAD2 signaling was present in all these lines. Pharmacological inhibition of ACVR1C signaling using SB505124, or genetic downregulation of the receptor using shRNA potently suppressed invasion, growth, survival, and reduced the protein levels of the mesenchymal markers ZEB1 and Snail. The inhibitory effects on invasion, growth, and proliferation were recapitulated by knocking down SMAD2, but not SMAD3. Finally, in an orthotopic zebrafish model of retinoblastoma, a 55% decrease in tumor spread was noted (p=0.0026) when larvae were treated with 3 μM of SB505124, as compared to DMSO. Similarly, knockdown of ACVR1C in injected tumor cells using shRNA also resulted in a 54% reduction in tumor dissemination in the zebrafish eye as compared to scrambled shRNA control (p=0.0005). Our data support a role for the ACVR1C/SMAD2 pathway in promoting invasion and growth of retinoblastoma.

Genome-wide analysis reveals genetic diversity, linkage disequilibrium, and selection for milk traits in Chinese buffalo breeds

“…HYAL4 and its paralog gene SPAM1 has demonstrated to be similar in structure to hyaluronidases that were one of the major glycosaminoglycans of the extracellular matrix involved in cell proliferation, migration, and differentiation [53–55]. ACVR1C is a type I receptor for the TGFB family of signaling molecules that plays a role in cell differentiation, growth arrest, and apoptosis [56]. Numerous studies have demonstrated that DEPTOR is the negative regulator of the mTORC1 and mTORC2 signaling pathways, which play a vital role in cell growth, metabolism, and disease [57, 58].…”

History and Genetics of Retinoblastoma

“…A three-fold increase was noted in mRNA levels of ACVR1C/ ALK7 in retinoblastomas invading the optic nerve. This suggests that ACVR1C/ SMAD2 pathway has a function in promoting invasion and growth of RB [60].…”

Modeling Cancer Using Zebrafish Xenografts: Drawbacks for Mimicking the Human Microenvironment

“…In the most recent studies, the authors injected retinoblastoma cells intravitreally and observed how the cancer cells were able to disseminate outside the eye, and how spread was reduced when fish were treated with different inhibitors to block transcriptional pathways, potentially related to the development of the disease. These results may have translational value, opening the door to the discovery of new therapies for retinoblastoma [ 138 , 139 ]. Additionally, a novel orthotopic xenograft model for conjunctival melanoma has been recently established by retro-orbital injection, to mimic primary tumor spread and to test the possible repurposing of the anti-tumor ruthenium-based photosensitizer TLD1433 for retinoblastoma [ 124 ].…”