CDKN1B and telomere syndrome: Following proliferative stimuli, MES-SA cells (established from primary STS) displayed high levels of p27 coupled with low levels of ERK1/2 activation and EGR1 expression, while HS-913T cells (established from metastatic STS) displayed low/null p27 levels, high ERK1/2 activation and EGR1 expression (Figure 8A and 8B).