Folia Biologica
Journal of Cellular and Molecular Biology, Charles University 

Long noncoding RNAs (lncRNAs) are known to play critical roles in the progression of osteosarcoma. Despite their recognized importance, the specific biological functions of lncRNAs in osteosarcoma remain unclear. In this context, prostate cancer-associated transcript 7 (PCAT7) has been identified as a bone metastasis-related lncRNA through the analysis of The Cancer Genome Atlas dataset. In this study, we investigated the expression of PCAT7 in osteosarcoma cells, particularly those exhibiting resistance to doxorubicin, a widely used chemotherapeutic agent in clinic. Functional assays including cell growth, invasion and apoptosis were conducted to elucidate the impact of PCAT7 inhibition on osteosarcoma cells, focusing on sensitivity to doxorubicin treatment. To understand the underlying molecular mechanisms, the interaction between PCAT7, miR-324-5p, and the TGF-β/SMAD signalling pathway was further explored. The study revealed that PCAT7 is up-regulated in osteosarcoma cells with doxorubicin resistance. Inhibition of PCAT7 could enhance the sensitivity to doxorubicin treatment by reducing cell growth, suppressing cell invasion and increasing cell apoptosis. Mechanistically, PCAT7 was shown to activate the TGF-β/SMAD signalling pathway by up-regulating the expression of TGFBR1 through sponging miR-324-5p. These findings unveil a novel mechanism contributing to the constitutive activation of TGF-β signalling in osteosarcoma. Targeting PCAT7 may offer a promising avenue for therapeutic interventions in osteosarcoma by disrupting the aberrant TGF-β signalling, thus presenting a potential strategy to improve treatment outcomes in this challenging cancer.

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