Two patients with multiple myeloma who appeared to be producing ammonia are reported. Both patients showed hyperammonemia and amino acid disturbances, such as a low Fischer ratio. One patient had Bence Jones protein (λ) type myeloma and became comatose, but the hyperammonemia and disturbance of consciousness were improved by chemotherapy for the myeloma. The other patient had IgA gκ type myeloma and somnolence and died of malignant pleurisy despite intensive chemotherapy. Autopsy showed widespread multiple myeloma and an almost normal liver. Ammonia levels in the supernatant of cultured myeloma cells from the patient’s pleural effusion increased almost linearly from the time of cell seeding. These observations showed that ammonia was produced at a high level by these human myeloma cells. We also found that one of the common myeloma cell lines, RPMI 8226, could produce ammonia as well.

A diagnosis of nonsecretory myeloma was established in two patients with anemia and proteinuria on the basis of the suppression of polyclonal immunoglobulins and the increase of plasma cells in the bone marrow. No paraprotein was detected in the serum or concentrated urine of these patients. However, a plaque-forming assay of bone marrow cells showed the secretion of monoclonal immunoglobulin by the myeloma cells. Moreover, renal biopsies from both patients indicated the deposition of monoclonal light chains in the glomerular mesangium and basement membrane, as well as in the tubular basement membrane, a pattern consistent with light-chain deposition disease. These observations suggested that the secreted paraprotein disappeared rapidly as a result of enhanced catabolism or deposition in organs such as the kidney, producing severe proteinuria and chronic renal failure. The plaque-forming assay is a useful technique for the demonstration of this type of nonsecretory myeloma, pseudo-nonsecretory myeloma.

Cell line KHM-2B expressing two oncogene products, c-myc and bcl-2, was established from a patient with actute lymphocytic leukemia with an 8; 14 and 14; 18 chromosome translocation. Surface marker studies of the cell line showed that the cells were positive for HLA-DR, CALLA (CD10), Bl (CD20) and B4 (CD19), but negative for Tl 1 (CD2). The fresh cells from peripheral blood of the patient had no surface immunoglobulins, whereas KHM-2B cells were positive for μ·λ type surface immunoglobulin. A cytogenetic analysis of the cell line revealed two translocations, t (8;14) (q24;q32) and t( 14; 18)(q32;q21). Rearrangement of the c-myc and bcl-2 genes was detected by Southern blot analysis of the KHM-2B DNA. Northern blot analysis revealed production of c-myc and bcl-2 mRNAs. These results indicated that two oncogenes were activated by two translocations to immunoglobulin genes.

A myeloma cell line (KHM-4) from a patient with multiple myeloma and idiopathic hyperammonemia, and another myeloma cell line (RPMI8226) were seen to have activity to form ammonia from arginine. High activity of ornithine transcarbamylase (OTC), a hepatic urea cycle enzyme, was detected in these cell lines. OTC of these cells was much more heat-stable than the liver enzyme, and did not cross-react with an antibody against the liver enzyme. As the OTC activity was also detected in the culture medium of the myeloma cells and because the activity was markedly decreased by the antimycoplasma drug MC-210, the OTC activity was assumed to be associated with mycoplasma infection. Polymerase chain reaction, using degenerate oligonucleotide mixtures corresponding to the two highly conserved sequences of OTC, amplified a DNA sequence that apparently encodes a portion (about 67% in length) of mycoplasma OTC. The predicted amino acid sequence of the mycoplasma enzyme was 33-47% identical with those of the enzymes of bacteria, yeast and mammals.