Abstract
BackgroundOsteosarcoma (OSA) is the most common bone cancer in canines. Both transforming growth factor beta (TGFβ) and Hippo pathway mediators have important roles in bone development, stemness, and cancer progression. The role of Hippo signalling effectors TAZ and YAP has never been addressed in canine OSA. Further, the cooperative role of TGFβ and Hippo signalling has yet to be explored in osteosarcoma. To address these gaps, this study investigated the prognostic value of TAZ and YAP alone and in combination with pSmad2 (a marker of active TGFβ signalling), as well as the involvement of a TGFβ-Hippo signalling crosstalk in tumourigenic properties of OSA cells in vitro. An in-house trial tissue microarray (TMA) which contained 16 canine appendicular OSA cases undergoing standard care and accompanying follow-up was used to explore the prognostic role of TAZ, YAP and pSmad2. Published datasets were used to test associations between TAZ and YAP mRNA levels, metastasis, and disease recurrence. Small interfering RNAs specific to TAZ and YAP were utilized in vitro alone or in combination with TGFβ treatment to determine their role in OSA viability, proliferation and migration.ResultsPatients with low levels of both YAP and pSmad2 when evaluated in combination had a significantly longer time to metastasis (log-rank test, p = 0.0058) and a longer overall survival (log rank test, p = 0.0002). No similar associations were found for TAZ and YAP mRNA levels. In vitro, TAZ knockdown significantly decreased cell viability, proliferation, and migration in metastatic cell lines, while YAP knockdown significantly decreased viability in three cell lines, and migration in two cell lines, derived from either primary tumours or their metastases. The impact of TGFβ signaling activation on these effects was cell line-dependent.ConclusionsYAP and pSmad2 have potential prognostic value in canine appendicular osteosarcoma. Inhibiting YAP and TAZ function could lead to a decrease in viability, proliferation, and migratory capacity of canine OSA cells. Assessment of YAP and pSmad2 in larger patient cohorts in future studies are needed to further elucidate the role of TGFβ-Hippo signalling crosstalk in canine OSA progression.
Highlights
Osteosarcoma (OSA) is the most common bone cancer in canines
Cell-line dependent effects of Transcriptional co-activator with a PDZ binding motif (TAZ) and Yes associated protein (YAP) depletion on cell proliferation Since a reduction in cell viability caused by YAP or TAZ knockdown in various OSA cell lines could result from an effect on cell survival, cell proliferation, or both, we focused on assessing the role of TAZ, YAP, and Transforming growth factor beta (TGFβ) signalling on cell proliferation exclusively
The potential association between YAP, metastasis and survival appears to be limited to protein levels, as we did not observe any associations with metastasis, survival or recurrence when we looked at mRNA levels of TAZ/WWTR1 or YAP1 alone or in combination with a TGFβ signature, using published datasets (Figs. 3 and 4, and data not shown)
Summary
Osteosarcoma (OSA) is the most common bone cancer in canines. Both transforming growth factor beta (TGFβ) and Hippo pathway mediators have important roles in bone development, stemness, and cancer progression. The cooperative role of TGFβ and Hippo signalling has yet to be explored in osteosarcoma To address these gaps, this study investigated the prognostic value of TAZ and YAP alone and in combination with pSmad (a marker of active TGFβ signalling), as well as the involvement of a TGFβ-Hippo signalling crosstalk in tumourigenic properties of OSA cells in vitro. The standard of care (SOC) for canine osteosarcoma (OSA) currently consists of limb amputation or limb-sparing surgery and chemotherapy With this treatment, the median survival time is 8–12 months and metastasis to the lungs is primarily responsible for patient’s mortality [2, 3]. The three TGFβ isoforms classically signal via the Smad pathway, involving Smad2/3 and Smad4 This is initiated by TGFβ binding to a TGFβ receptor type II (TβRII) homodimer, which facilitates the formation of a complex with a TGFβ receptor type I (TβRI) homodimer. The R-Smads and co-Smad complex translocates to the nucleus to modulate gene expression through cooperation with other transcription factors, co-activators, and co-repressors (reviewed in [6])
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.
