Tumor expression studies indicate that HEM-1 is unlikely to be the active factor in oncogenic osteomalacia

HEM-1 was isolated as a putative factor responsible for oncogenic osteomala cia by Kumar et al, (Proc Assoc Am Phys 107:296-305; 1995), The cDNA was id entified on the basis of PTH-like immunoreactivity; however, no studies hav e been reported of the expression of HEIM-1 mRNA in oncogenic osteomalacia tumors. In this study, expression of HEM-1 mRNA was investigated in two onc ogenic osteomalacia tumors and in a series of normal tissues, An HEM-1 PCR product was amplified from a cDNA library from one of the tumors, with six base changes identified, as compared with the published sequence. No expres sion was detected, however, in the oncogenic osteomalacia tumors either by Northern blot analysis or by reverse transcriptase PCR, This indicates that , although a region of HEM-1 sequence is present in the tumor cell cDNA lib rary, any HEM-1 expression must be at very low levels. It is unlikely, ther efore, that the HEM-1 product is the active factor responsible for oncogeni c osteomalacia, In the normal tissues examined, human placenta, fibroblasts , parathyroid gland, liver, fetal bone, and rat kidney cortex, HEM-1 mRNA w as not detected, suggesting that it does not have a physiological role in t hese tissues, (Bone 23:549-553; 1998) (C) 1998 by Elsevier Science Inc. All rights reserved.