QUANTITATION OF SOMATOSTATIN RECEPTOR-TYPE-2 GENE-EXPRESSION IN NEUROBLASTOMA CELL-LINES AND PRIMARY TUMORS USING COMPETITIVE REVERSE TRANSCRIPTION-POLYMERASE CHAIN-REACTION

We previously reported the presence of somatostatin (SS-14)-binding si tes in a wide panel of human neuroblastoma (NB) tumor cell lines, Give n that the adrenal gland and its relative embryonal and adult tumors e xpress an abundance of mRNA for somatostatin receptor type 2 (sst2) mR NA, we studied the quantitative expression of sst2 in 6 NE cell lines and 15 primary tumors using competitive reverse transcription (RT)-PCR . This method uses an insertion mutant of the target gene as a competi tor for the RT-PCR reaction, thus allowing exact quantitation of sst2 mRNA abundance, We found expression of specific transcripts for sst2 i n all of the NE cell lines and tumors investigated (range, 9 x 10(5)-4 x 10(9) molecules/mu g RNA), In NE cells, the expression of sst2 was highly correlated with SS-14-binding sites (R = 0.93), In primary tumo rs, sst2 was positively related to the expression of the neuroendocrin e marker secretogranin II (P < 0.05) and negatively related to N-myc a mplification (a poor prognostic factor, P < 0.005) and metastatic diss emination (P < 0.05), In addition, Kaplan-Meier curves indicate that s st2 expression is positively related to survival (P = 0.01), In a pati ent with stage TVs disease (a spontaneously regressing form), we found the highest sst2 expression (4 x 10(9) molecules/mu g RNA), a value r elatively similar to that of normal adrenal, In conclusion, these data indicate that quantitation of sst2, as assessed with competitive RT-P CR, could represent a new prognostic tool in the neuroendocrine tumor NB. Since sst2 recognizes octreotide with high affinity, these finding s could also have both diagnostic and therapeutic value.