The somatostatin analog octreotide inhibits growth of interleukin-6 (IL-6)-dependent and IL-6-independent human multiple myeloma cell lines

Somatostatin and its analogs can inhibit growth in several cell types, in p art by interfering with insulin-like growth factor-I (IGF-I) signaling. Our previous studies point to the importance of paracrine and autocrine IGF-I in the support of growth and survival of human multiple myeloma (MM) cell l ines. In this report, we have investigated the potential role of a somatost atin analog, octreotide, in regulating growth and/or survival in MM. The re sults show that all MM cell lines express functional somatostatin receptors (sst). The MM cell lines express the subtypes sst(2), sst(3) and predomina ntly sst(5) as determined by reverse-transcriptase polymerase chain reactio n and fluorescence-activated cell sorter analysis. Octreotide inhibited the growth of both the interleukin-6 (IL-6)-dependent and the IL-independent M M cell lines. The effect is mainly cytostatic, resulting in 25% to 45% grow th inhibition, and in three of eight of the MM cell lines a weak induction of apoptosis was recorded. Our results also show that octreotide may act as an inducer of apoptosis in primary B-B4(+) plasma cells isolated from bone marrow of MM patients. In conclusion, the results show a novel pathway for growth inhibition of MM cells: the activation of somatostatin receptor sig naling. (C) 1999 by The American Society of Hematology.