Biochemical Role of Circulating microRNAs Expression as Diagnostic Markers for Non-Hodgkin's Lymphoma Patients

Lymphomas are a fairly common malignancy accounting for approximately half of all newly diagnosed hematological neoplasms, and they comprise the sixth most common group of malignancies worldwide in both men and women, With marked geographic variations and affecting more males than females within the age range of 1 to 85 years but peaking within the second decades of life (Oluwasola AO et al., 2011, Roman E et al., 2011 and Jemal A et al., 2010) . Lymphomas have traditionally been classified as either Hodgkin's lymphoma (HL) or non-Hodgkin's lymphoma (NHL) based on the presence or absence of the Reed-Sternberg (RS) cell on histology. (Fitzmaurice C et al., 2017). Non-Hodgkin's lymphoma (NHLs) comprise a wide class of lymphoid neoplasms that evolve from the clonal expansion of mature B, T and natural killer (NK) cells in different stages of development (Morton, L.M. et al., 2014 and Schmitz R et al., 2009). NHLs are the most prevalent hematopoietic neoplasms, accounting for approximately 4.3% of all cancer diagnoses (Sant, M. et al., 2010) , Of them, B cell NHL accounts for approximately 30% of all lymphoid neoplasms, followed by HL (8%) and T/NK neoplasms (5%) (Morton, L.M. et al., 2006).

MicroRNAs (miRNAs) are a class of small, naturally occurring, noncoding and single-stranded RNA molecules (18, 22 nucleotides) that function as post-transcriptional regulators by directly cleaving target messenger RNA (mRNA) or translational repression (Bartel DP. Et al., 2004). The discovery of miRNA has exposed a new layer of gene expression regulation that affects many physiological and pathological processes of life (Lawrie CH. Et al., 2013).

Many abnormal miRNA expression patterns are found in various human malignancies, and certain miRNAs play roles as oncogenes or tumor suppressors (Ling N et al., 2013). Certain miRNAs have been found to characterize various subtypes of NHL and have important roles in B-cell differentiation and lymphomagenesis (Zhang J et al., 2009, Malumbres R et al., 2009, Basso K et al., 2009 and Auer RL et al., 2011). Recently, many studies had shown that tumor cell-specific miRNAs were detectable in the plasma and serum of patients with cancer. Therefore, miRNAs may be served as good biomarkers for early detection, diagnosis, and follow up of patients with cancer (Cortez MA et al., 2012).