Metabolism of Bence Jones proteins in multiple myeloma patients and in patients with renal disease

Renal manifestations of plasma cell dyscrasias: an appraisal from the patients' bedside to the research laboratory

One of the most prominent features of plasma cell dyscrasias is the frequent occurrence of renal dysfunction. Renal insufficiency is a common finding with elevated serum creatinine in more than 50% of patients with multiple myeloma at the time of diagnosis. Renal failure is the second most common cause of death in myeloma surpassed only by infections. The reasons for renal failure are multifactorial and early accurate diagnosis of the renal alterations may significantly impact morbidity and survival. Renal failure may result from selective glomerular, tubular interstitial, or vascular pathology or from a combination of pathologic events. The disorders associated with plasma cell dyscrasias include those characterized by monoclonal light chain deposition, encompassing AL-amyloidosis, in addition to the less well-characterized entities, such as heavy chain deposition disease and heavy chain amyloidosis. Therefore, it is more accurate to refer to them as monoclonal immunoglobulin deposition diseases. Staining of renal biopsy specimens for kappa and lambda light chains using immunofluorescence techniques and more sophisticated advanced diagnostic techniques such as immunoelectron microscopy permit detailed characterization of the various renal pathologic manifestations. Renal biopsies can identify monoclonal immunoglobulin deposition, and nephrologists have an opportunity to detect an underlying plasma cell dyscrasia early in its clinical course before overt hematologic alterations become manifest and irreversible renal damage has occurred. The overall spectrum of clinical and pathologic manifestations of monoclonal immunoglobulin deposition renal diseases has expanded considerably in recent years. Recent developments in the research arena promise new therapeutic interventions aimed at avoiding or ameliorating renal damage and even promoting reversal of some of the pathologic alterations. Currently, the 5-year survival rate in myeloma is 29% in white patients and 30% in African-American patients, a rather modest improvement from 24% in the 1970s. Bone marrow ablation followed by transplantation is available as an alternative mode of therapy that may be extraordinarily helpful in a subset of patients with early myeloma.

Systemic lambda light-chain deposition in a patient with myeloma

Systemic lambda light-chain deposition occurred in a 73-year-old man with myeloma. An initial renal biopsy specimen showed the features of myeloma kidney. When he died 22 months later lambda light chains were detected by immunofluorescence in kidneys, liver, spleen, and heart. They were probably responsible for cardiac dysfunction and the fatal arrhythmia. It is suggested that in this patient deposition was due to a structural alteration of the light chains, possibly induced by cyclophosphamide.

Synthesis and metabolism of Bence Jones protein and calculation of tumour burden in patients with Bence Jones myeloma

Synthesis and metabolism of Bence Jones protein was measured in seven patients with Bence Jones myeloma. Using the plasma and urine levels of 125I-labelled Bence Jones protein, it was possible to calculate the fractional catabolic rate (FCR), fractional proteinuric rate (FPR), and fractional metabolic rate (FMR) for the individual patients. There was a high degree of correlation between decreased metabolism and reduced creatinine clearance (P < 0.001). Ideal regression equations (linear and nonlinear) relating FCR, FPR and FMR with fractional creatinine clearance (FCC) were calculated. Using these regression equations plus measured values for the synthetic rates of light chain for bone marrow plasma cells, the myeloma cell mass or tumour burden was measured in each patient. Correlations between these measured cell mass values and those derived from clinical staging were reasonably good. However, for the lambda (gamma) Bence Jones myeloma patients, the measured cell mass values were significantly higher than predicted from clinical staging. Further studies will be necessary to validate this latter observation. It is hoped that this study will serve as a basis for a comprehensive schema allowing accurate cell mass measurement and staging of Bence Jones myeloma.

Bence Jones proteins and light chains of immunoglobulins. XV. Effect of corticosteroids on synthesis and excretion of Bence Jones protein

The effect of corticosteroids and cytotoxic chemotherapeutic agents on the excretion of Bence Jones protein was determined for periods of 1 - 62 mo in 29 patients with multiple myeloma and Bence Jones proteinuria. The amount of protein present in 24-h urine specimens collected before treatment and at frequent intervals during monthly treatment cycles was determined. Striking variations occurred in the amount of Bence Jones protein excretion; these changes were especially evident when 75 mg of prednisone were given daily for 7 days as part of a monthly chemotherapeutic regimen. Within the 7-day period seven patients showed essentially no decrease (<25%), whereas 13 and 9 patients had a moderate decrease (25-75%) or a marked decrease (>75%), respectively, in Bence Jones proteinuria as compared to pre-treatment values. The decrease in excretion of Bence Jones protein during this period was attributed mainly to corticosteroid therapy because of the transient nature of the response in most patients and the lack of such response in three patients when the hormone was omitted. Biosynthetic studies were performed to determine in vitro the effect of corticosteroids on Bence Jones protein synthesis. Plasma cells obtained from the bone marrow of 13 patients were incubated in a growth medium containing (14)C-labeled lysine and isoleucine and prednisone in concentrations up to 240 mug/ml, and the amount of Bence Jones protein synthesized was determined immunochemically. No differences in viability were apparent between untreated and prednisone-treated cells. The type of response exhibited by an individual patient in the percent decrease of Bence Jones protein excreted after 7 days of prednisone treatment was comparable to the percent decrease in newly-synthesized Bence Jones protein secreted by tumor cells when cultured in the presence of prednisone at a concentration of 120 mug/ml. The marked differences in the capacity of corticosteroids to affect Bence Jones protein synthesis appear to reflect a biochemical heterogeneity among plasma cell neoplasms.

Retinol binding protein in serum and in urine of glomerular and tubular nephropathies

RBP behavior was studied in different kidney diseases. Serum RBP was increased in chronic renal diseases when the serum creatinine increased. RBP clearance and RBP clearance as a percentage of albumin clearance increased when GFR decreased; this is more evident in tubular kidney diseases. Urinary RBP loss as a percentage of urinary albumin loss increased especially in kidney diseases with persistent tubular lesions.

Manifestations of systemic light chain deposition

In two patients with terminal renal failure, manifestations of disease developed in multiple organ systems. One had a previous diagnosis of multiple myeloma with kappa light chain proteinemia and proteinuria. The other had idiopathic lobular glomerulonephritis. Hepatic and neurologic abnormalities developed in both; in the latter gastrointestinal, cardiac and endocrine disease developed as well. Clinical and pathologic correlations suggest that the retention and tissue deposition of light chains produced the organ dysfunction, inasmuch as free kappa light chain determinants were demonstrated histologically in the clinically affected organs. The deposition in these patients may be an extreme example of a common but previously unrecognized form of plasma cell dyscrasia.

The renal handling of low molecular weight proteins. II. Disorders of serum protein catabolism in patients with tubular proteinuria, the nephrotic syndrome, or uremia

The present study was directed toward determining the role of the kidney in the metabolism of various classes of serum proteins and to define the urinary protein excretion patterns and the pathogenesis of disorders of protein metabolism in patients with proteinuria. To this end, the metabolic fates of a small protein, lambda-L chain (mol wt 44,000), and a protein of intermediate size, IgG (mol wt 160,000), were studied in controls and patients with renal disease. Controls metabolized 0.28%/hr of circulating IgG and 22.3%/hr of circulating lambda-L chain. All the IgG and 99% of the lambda-L chain was catabolized with the remaining lambda-L chain lost intact into the urine. The kidney was shown to be the major site of catabolism for small serum proteins. Three distinct disorders of protein metabolism were noted in patients with renal tubular disease and tubular proteinuria, glomerular disease (the nephrotic syndrome), and disease involving the entire nephrons (uremia), respectively. Patients with renal tubular disease had a 50-fold increase in the daily urinary excretion of 15-40,000 molecular weight proteins such as lysozyme and lambda-L chains. Serum IgG and lambda-L chain survivals were normal; however, the fraction of the over-all lambda-L chain metabolism accounted for by proteinuria was increased 40-fold whereas endogenous catabolism was correspondingly decreased. Thus, tubular proteinuria results from a failure of proximal tubular uptake and catabolism of small proteins that are normally filtered through the glomerulus. Patients with the nephrotic syndrome had a slight increase in lambda-L chain survival whereas IgG survival was decreased and the fraction of IgG lost in the urine was markedly increased. Here, abnormal glomerular permeability to proteins of intermediate size is the basic abnormality. Patients with uremia had a normal IgG survival but a four to 10-fold prolongation of lambda-L chain survival due to loss of entire nephrons, the major site of metabolism of these proteins. This results in an increase (up to 10-fold) in the serum concentration of lambda-L chain, lysozyme, and other small biologically active proteins, a phenomenon that may be of importance in causing some of the manifestations of the uremic syndrome.