Aberrant expression of SPAG6 may affect the disease phenotype and serve as a tumor biomarker in BCR/ABL1-negative myeloproliferative neoplasms

Sperm-associated antigen 6 (SPAG6) is a newly identified cancer-testis antigen that has been revealed to contribute to the occurrence and development of various types of human cancer, such as ovarian, bladder, breast and lung cancer. However, to the best of our knowledge, the expression levels of SPAG6 in breakpoint cluster region (BCR)/ABL1-negative myeloproliferative neoplasms (MPNs) have not been investigated previously. Using reverse transcription-quantitative PCR and different tissue staining techniques, the present study revealed that SPAG6 was expressed by MPN cells, both at the mRNA and protein levels, and that nucleated erythroid precursors and megakaryocytes expressed the highest levels of SPAG6. In addition, SPAG6, which is known as a microtubule-associated protein, was found to exhibit nucleic, cytoplasmic or both cytoplasmic and nucleic subcellular localization patterns within the same patient or cell type; however, it did not always co-localize with β-tubulin. Furthermore, SPAG6 expression was revealed to be associated with fewer splenomegaly [P=0.015 for polycythemia vera (PV) and essential thrombocythemia (ET); and P=0.012 for primary myelofibrosis (PMF)] and myelofibrosis events (P=0.014 for PV and ET; and P=0.004 for PMF). In patients with PMF, upregulated expression levels of SPAG6 were also found to be associated with lower white blood cell counts (P=0.042) and lactate dehydrogenase levels (P=0.012), and higher hemoglobin levels (P=0.031) and platelet counts (P=0.025). In addition, the receiver operating characteristic curve analysis indicated that SPAG6 may be a potential biomarker for distinguishing MPN cases from healthy individuals. In conclusion, to the best of our knowledge, the present study is the first to report that aberrant SPAG6 expression may affect the disease phenotype and serve as a tumor biomarker in BCR/ABL1-negative MPNs.