CCN1 and osteosarcoma: CCN1 and CCN2 do not promote osteosarcoma cell proliferation per se but protect cells from apoptosis and decrease chemotherapeutic efficacy (Chen et al. 2013a; Fromigue et al. 2011; Habel et al. 2015, 2019; Huang et al. 2016; Tsai et al. 2014a, 2014b, 2014c; Zhang et al. 2013).