ABSTRACT
The ability of both somatostatin (SS) and its stable analogues to inhibit cell growth depends on the stimulation of specific membrane receptors (SSTR1-5), which belong to the G protein-coupled receptor family. Accumulating evidence suggests that the SSTR2 plays a major role in mediating cell cycle arrest, and it is also clear that SHP-1, a cytoplasmic phosphotyrosine phosphatase (PTP), is an essential component of the SSTR2-mediated cytostatic effect. In contrast, the possibility that SSTR2 activation may also lead to increased apoptosis is still beyond debate, despite SHP-1 activation is also able to promote cell death in several cell types. In the present work we have investigated the ability of SSTR2 to induce apoptosis in HL-60 cells. We have found that HL-60 cells uniquely express the SSTR2 subtype, and that stimulation of SSTR2 with the SS analogue SMS 201-995 results in an increased cell death. In all, these findings demonstrate that activation of SSTR2 promotes apoptosis in HL-60 cells. Moreover, in contrast with the proapoptotic mechanism previously reported for SSTR3, cell death induced by activation of SSTR2 is independent from accumulation of p53.
