Electrophoretic Analysis of Abnormal Data Discovered by Serum Enzyme Testing].

Lactate dehydrogenase (LD) isozymes are formed by random combinations of two different subunits encoded by LDHA and LDHB. There are a number of reasons for unusual LD electrophoretic isozyme patterns. An abnormal electrophoretic pattern may result from additional LD fractions, altered mobility, an altered molecular structure, or the distortion of one or more normal bands. The distortion of normal bands may be caused by immunoglobulin or other protein binding, genetic variants, or tumor production. The genetic mutations occasionally cause hereditary deficiency of the LD-A subunit or LD-B subunit, yielding specific LD isozyme patterns in serum and erythrocytes. Different LD isozyme patterns in cancer patients possibly originate from changes in expression of LDHA or LDHB due to other regulatory genes or promoter methylation or from deletions, duplications, or changes in gene copy numbers. We encountered a patient with retinoblastoma and a cell line, R51, that showed an LD-1-dominant isozyme pattern. We found that the abnormal isozyme pattern was mainly due to transcriptional silencing by aberrant DNA methylation in the promoter region of the LDHA gene. On the contrary, high LDHA was observed in gastrointestinal cancer, prostate cancer, and breast cancer tissues according to promoter hypermethylation of LDHB. The LD isozyme patterns in cancer patients reflect original tissues or cells regulated by the gene dosage effect or gene expression, which are both genetically and epigenetically controlled (especially aberrant DNA methylation).

Citation

Masato Maekawa. Electrophoretic Analysis of Abnormal Data Discovered by Serum Enzyme Testing]. Rinsho byori. The Japanese journal of clinical pathology. 2014 Nov;62(11):1088-93

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PMID: 27509726

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