β‐Catenin transcriptional activity is minimal in canine osteosarcoma and its targeted inhibition results in minimal changes to cell line behaviour

Abstract

Canine osteosarcoma (OS) is an aggressive malignancy associated with poor outcomes. Therapeutic improvements are likely to develop from an improved understanding of signaling pathways contributing to osteosarcoma development and progression. The Wnt signaling pathway is of interest for its role in osteoblast differentiation, its dysregulation in numerous cancer types, and the relative frequency of cytoplasmic accumulation of β-catenin in canine OS. This study aimed to determine the biological impact of inhibiting canonical Wnt signaling in canine OS, by utilizing either β-catenin siRNA or a dominant-negative TCF construct. There were no consistent, significant changes in cell line behavior with either method compared to parental cell lines. Interestingly, β-catenin transcriptional activity was 3-fold higher in normal canine primary osteoblasts compared to canine osteosarcoma cell lines. These results suggest canonical Wnt signaling is minimally active in canine osteosarcoma and its targeted inhibition is not a relevant therapeutic strategy.

Transition between canonical to non-canonical Wnt signaling during interactions between mesenchymal stem cells and osteosarcomas

“…Therefore, the canonical Wnt/-catenin pathway probably did not contribute to the enhancement of OS aggressiveness caused by MSCs and it may occur via secretion of array of chemokine and cytokine and signaling ques that are known to interact with cancer cells. Those results are consistent with previous studies on OS, which indicated the absence of -catenin in the nucleus and pointed to an inactivation of the canonical Wnt pathway [41][42][43][44][45][46]. However, opposite trends of -catenin and c-Myc expression were identifi ed in MSCs cultures in comparison with OS and co-cultures, which may indicate that -catenin was involved in transcription of other target genes besides cMyc.…”

Aberrant activation of Wnt/β-catenin signaling drives proliferation of bone sarcoma cells

“…However, contradictory to these findings, the Wnt/β-catenin pathway was inactivated in osteosarcoma and that the loss of Wnt-β-catenin activity induces osteosarcoma development [ 33 ]. Similarly, Piskun CM et al have demonstrated that β-catenin transcriptional activity was found to be three-fold higher in the normal primary canine osteoblasts relative to these canine osteosarcoma cell lines [ 34 ]. Bongiovanni L et al also found increased β-catenin intensity and nuclear localization in canine osteoblasts compared to canine osteosarcoma clinical samples [ 35 ].…”

Canine sarcomas as a surrogate for the human disease

“…Overexpression of RB1 in canine OSA cells from the first group shifted their gene expression profiles to more closely resemble those of the second group through altered E2F signaling (Moriarity et al, 2015). In addition to these more global evaluations of gene expression, a variety of studies have linked activation of signaling pathways including receptor tyrosine kinase-MAP kinase, Hedgehog (O’Donoghue et al, 2010; Shahi, Holt, & Rebhun, 2014), Notch (Dailey et al, 2013), Wnt (de Sa Rodrigues, Holmes, Thompson, Newton, & Stein, 2017; Piskun & Stein, 2016; Stein, Holmes, Muthuswamy, Thompson, & Huelsmeyer, 2011), STAT3 (Fossey et al, 2009), TGFβ, cellular survival (Shoeneman et al, 2012), ezrin (Hong et al, 2011; Khanna et al, 2004) and MTOR (Gordon, Ye, & Kent, 2008) in the pathogenesis and metastasis of canine OSA. These studies have been summarized in a recent reviews of canine (Fenger et al, 2014) and human (Kansara, Teng, Smyth, & Thomas, 2014) OSA (Table 2).…”