Impact of the Expression of Genes Related to T Regulatory Cells on the Survival of Patients with Multiple Myeloma

Multiple myeloma (MM) development involves a series of genetic alterations and changes in the bone marrow (BM) microenvironment, favoring the growth of the tumor and failure of local immune control. T regulatory (Treg) cells play an important role in the maintenance of self-tolerance and modulation of overall immune responses against infections and tumor cells. T-helper-17 (Th17) cells, on the other hand, exhibit a critical function in eradicating extracellular pathogens and tumor cells. The balance between Tregs and Th17 cells may be essential for maintaining homeostasis of anti-tumor immunity. We have previously shown that genes related to Tregs, such as CTLA-4 and FOXP3, are overexpressed in the BM of myeloma patients. The aim of the present study was to investigate whether the myeloma-related overexpression of genes related to Tregs and/or Th17 cells, in addition to their role as biomarkers and possible therapeutic targets, also has a prognostic impact on this incurable disease.

Forty-six newly diagnosed and treatment-naïve MM patients were included into this study. Expression of 4 genes related to Tregs (FOXP3, CTLA-4, TGFB1, CD25) was determined by quantitative real-time PCR (qPCR) in BM aspirates using TaqMan Gene Expression Inventoried Assays (Applied Biosystems). Houesekeeping genes GAPDH, BGUS and βactin were chosen as endogenous controls. Target genes were considered differentially expressed in tumor samples when their expression levels showed at least a 2-fold increment or decrease in comparison to normal samples. Overall survival (OS) time was calculated from the date of diagnosis of MM until death or last follow-up. Actuarial probabilities of OS were estimated according to the Kaplan-Meier method and the curves were compared using the log-rank test. The Cox's Regression Model was also employed to evaluate which variables could be considered independent prognostic factors.

According to the International Staging System (ISS) most patients included were in advanced stages (ISS-1: 6 cases, ISS-2: 13 cases, ISS-3: 23 cases; 4 patients not classified). Most patients received either dexamethasone/thalidomide or melphalan/prednisone/thalidomide as first-line treatment, depending on their age and performance status. 5 patients received high-dose chemotherapy and autologous stem cell transplantation. Median OS of MM patients was 16.8 (range 4.45–29.1) months. Univariate analysis indicated that stage (p=0.011) and expression of Treg-related gene (overexpression vs normal expression vs. underexepression) only FOXP3 (p=0.073) had an impact on the patients' prognosis. However, Cox Regression analysis showed that only the ISS stage (p = 0.0108, RR 5.04, CI 1.1526–22.1064) was an independent prognostic factor.

Despite a significant increase in the expression of genes related to Treg cells, our data showed no impact of those genes on overall survival of patients with MM. It could seem that it is now firmly established that the presence of Tregs does not at all influence the outcome of MM(Supported by Fapesp 2010/17668-6, Brazil).

No relevant conflicts of interest to declare.