POSTN and plasma cell myeloma: The periostin levels in the supernatants of the myeloma cell lines were higher comapred with those found in the supernatants of the ovarian cancer cell lines (mean±s.d.: 17.2±6.14 vs 2.98±1.92 ng/ml; P=0.001; levels of periostin in the RPMI+FBS was 0.595 ng/ml).