The expression of multiple cancer/testis antigens can potentially be used to detect circulating disease and clonal evolution in the peripheral blood of multiple myeloma patients

BACKGROUND: It is thought that cancer/testis antigens (CTAs) are expressed in a cascade-like manner in multiple myeloma as the disease progresses. In this pilot study, we investigated the co-expression of several CTAs in the peripheral blood (PB) during patient therapy to establish whether monitoring multiple CTAs allows for the prediction of relapse and clonal evolution. METHODS: We examined the co-expression of MAGEC1, MAGEA3, PRAME, and BAGE2 via quantitative reverse transcription-polymerase chain reaction (qRT-PCR) duplex assays in the PB mononuclear cells of 10 patients on chemotherapy at 3-month intervals, and correlated the levels to those of two basic clinical monitoring markers, serum b-2-microglobulin and serum M protein. Clonal evolution was investigated using flow cytometry to label the circulating malignant stem cell components with MAGEC1, PRAME, and MAGEA3 antibodies. RESULTS: Simultaneous monitoring of MAGEC1/PRAME provided sensitive detection of circulating malignant cells in easily accessible PB samples; transcript levels increased prior to changes in indicators of clinical relapse. While MAGEA3/BAGE2 expression levels did not offer earlier prediction of relapse, they provided insight into significant changes occurring within the malignant cell population; the addition of either CTA to a MAGEC1-monitoring panel allowed for better classification of the relapse event (clonal evolution), which in turn could potentially guide treatment strategies in the future. CONCLUSION: This pilot study supports the novel idea of determining the levels and CTA expression patterns of the total circulating malignant cell population (pro-B/pre-B stem cell progenitors and proliferating plasma cells) as an alternate disease monitoring methodology.