The distribution and potential prognostic value of SMAD protein expression in chronic lymphocytic leukemia

Abstract

The SMAD proteins are responsible for transducing signals from activated transforming growth factor-beta. This is the first study assessing the expression of SMAD-1/8, SMAD-2/3, SMAD-4, and SMAD-7 in chronic lymphocytic leukemia cells with regard to their clinical significance and potential prognostic value. Overexpression of SMAD-1/8 was observed in 160 chronic lymphocytic leukemia patients compared to 42 healthy volunteers (p = 0.023) and was associated with a more progressive course of the disease (p = 0.016). Moreover, the high expression of SMAD-1/8 correlated with other, well-established prognostic factors, including clinical stage (p = 0.010) and lymphocyte doubling time (p = 0.021). The expression of SMAD-4 was lower in chronic lymphocytic leukemia patients compared with the control group (p = 0.003). Importantly, lower SMAD-4 levels correlated with longer progression-free survival (p = 0.009), progressive course of the disease (p = 0.002), advanced clinical stage (p = 0.0004), elevated beta-2-microglobulin and lactate dehydrogenase levels (p < 0.05), shorter lymphocyte doubling time (p = 0.009), and CD38 antigen expression (p = 0.039). In addition, lower SMAD-4 expression correlated with lower apoptotic index (p = 0.0007) and lower expression of receptors for vascular endothelial growth factors VEGFR-1 and VEGFR-2. A significant association was found between the low expression of inhibitory protein SMAD-7 and both zeta-chain-associated protein kinase 70-negative cells (p = 0.04) and lower apoptotic index (p = 0.004). No differences were observed in SMAD-2/3 expression. In conclusion, our results demonstrate a significant correlation between greater SMAD-1/8 and lower SMAD-4 expression in chronic lymphocytic leukemia cells, as well as more progressive outcome and poor prognosis. These data provide supporting evidence that the expression of SMAD proteins plays an important role in disease development and may be considered as a novel, biologic prognostic factor in this disease.

TGF-β/SMAD Pathway Is Modulated by miR-26b-5p: Another Piece in the Puzzle of Chronic Lymphocytic Leukemia Progression

“…Altogether, our results suggest the existence of a TGF-β inactivation in primary CLL cells of progressive U-cases compared to stable patients. Although our data are not direct evidence of the cause of disease progression, they are in agreement with previous reports linking impairment of TGF-β pathway with poor clinical outcome in CLL [ 27 , 28 , 29 , 30 ]. In addition, these works propose that TGFβ-1 induces growth arrest in CLL cells, but about one-third of the patients are resistant to its effects [ 26 , 58 ].…”

“…TGF-β protein is a pleiotropic cytokine and exerts its effect on gene expression through transcription factors known as SMAD proteins. Specifically, in CLL, different works support the role of TGF-β pathway as a growth inhibitor of CLL cells [ 40 ], and recently, SMAD protein expression has been correlated with disease progression [ 29 ]. In view of these data and our previous results, we evaluated the activation of the TGF-β axis in stable and progressive U-CLLs by comparing mRNA levels of SMAD-2, SMAD-3, SMAD-4, and SMAD-7 as well as of two recognized target genes of the TGF-β pathway, cyclin-dependent kinase inhibitor 1A (p21 −Cip1 ) [ 41 ] and KLF10 (Kruppel Like Factor 10) [ 42 ].…”

“…Once activated, the receptor substrate SMADs (RSmads) forms a complex with SMAD-4, a binding partner common to all RSmads, and shuttles to the nucleus originating transcriptional activation and repression complexes to control the expression of hundreds of target genes in a given cell [ 25 ]. In CLL, an interesting work of Witkowska et al recently linked the expression levels of SMADs proteins with clinical evolution and shows that lower SMAD-4 protein levels correlate with progressive course of the disease [ 29 ]. From the three miRNAs up-regulated in the U-CLL subgroup, two of them, miR-26b-5p and miR-142-5p, have been described as targeting different SMADs proteins.…”

“…This pathway regulates not only cellular proliferation, differentiation, survival, and adhesion but also the cellular microenvironment [ 23 ]. Several works suggest that TGF-β inhibition promotes leukemic transformation [ 24 , 25 ], and, specifically in CLL, this has been postulated [ 26 , 27 , 28 , 29 ], but the molecular mechanisms that regulate this pathway during CLL progression remain unknown.…”

The BMP pathway: A unique tool to decode the origin and progression of leukemia

“…Finally, analysis of gene expression of the BMP signaling pathway in a cohort of 160 CLL patient samples showed alterations of SMAD1/8 that appeared overexpressed and correlated with a decrease in SMAD4 expression compared with control samples. High levels of SMAD1/8 transcripts expression were associated with poor prognosis [81]. Interestingly, gene expression analysis of two independent datasets showed that the levels of inhibitory Smads varied across different B-cell lymphomas [79].…”