Expression of signal transducer and activator of transcription 3 (STAT3) in primary central nervous system diffuse large B-cell lymphoma: a retrospective analysis of 17 cases

Clinicopathologic significance of MYD88 L265P mutation and expression of TLR4 and P-STAT3 in primary central nervous system diffuse large B-cell lymphomas

Patients with primary central nervous system lymphoma (PCNSL) have a prognosis poorer than that of systemic lymphoma patients. In patients with this condition, TLR4/STAT3 pathway alterations and the MYD88 L265P mutation may be viable targets for therapeutic intervention. The present study was, therefore, designed to identify clinicopathologic correlates of MYD88 mutations and TLR4/STAT3 pathway alterations in PCNSL. We detected TLR4 and p-STAT3 in 41.5% (22/53) and 43.4% (23/53) of PCNSL patients, respectively, while 60.4% of these patients (32/53) were found to harbor the MYD88 L265P mutation. TLR4 expression was found to be significantly associated with the presence of multiple brain lesions, while p-STAT3 expression was significantly linked to advanced age, the presence of multiple brain lesions, non-GCB histological findings, and non-CR status. The presence of the MYD88 L265P mutation was significantly linked to advanced age, the presence of multiple brain lesions, and DLBCL molecular subtype. Multivariate analyses additionally confirmed that elevated TLR4 and p-STAT3 expression levels are associated with a poorer PCNSL patient prognosis. Based on these findings, we hypothesize that signaling through the TLR4/MYD88/STAT3 pathway plays a key role in the pathogenesis of PCNSL.

STAT3 Activation Is Associated with Interleukin-10 Expression and Survival in Primary Central Nervous System Lymphoma

BACKGROUND

The findings from several studies have confirmed that signal transducer and activator of transcription 3 (STAT3) is constitutively phosphorylated in primary central nervous system lymphoma (PCNSL). However, the underlying mechanism and prognostic significance of STAT3 activation have not yet been clarified.

METHODS

The expression of STAT3, phosphorylated STAT3 (p-STAT3), and interleukin (IL)-10 was examined in 32 PCNSL samples using immunohistochemistry. The relationship between IL-10 expression and STAT3 phosphorylation was determined. In addition, the associations of the expression of these proteins with the clinical factors and survival were analyzed.

RESULTS

Expression of STAT3, p-STAT3, and IL-10 was detected in 28 (87.5%), 17 (53.1%), and 25 (78.1%) samples, respectively. IL-10 expression was significantly associated with STAT3 phosphorylation in PCNSL (P = 0.033). STAT3 phosphorylation and IL-10 expression were associated with the presence of multiple brain lesions (P = 0.004 and P = 0.027, respectively), suggesting that STAT3 activation might enhance the intracranial spread of tumors in PCNSL. The 2-year overall survival and progression-free survival (PFS) rates were 67.8% and 35.5%, respectively. Kaplan-Meier survival analysis demonstrated that STAT3 phosphorylation, IL-10 expression, and multiple brain lesions were significantly associated with PFS in those with PCNSL (P = 0.009, P = 0.030, and P = 0.040, respectively). However, Cox regression analysis indicated that only STAT3 phosphorylation was significantly associated with shorter PFS (hazard ratio, 3.22; 95% confidence interval, 1.24-8.37; P = 0.016).

CONCLUSION

Our results have indicated that STAT3 activation is closely related to IL-10 expression and that p-STAT3 might be a novel biomarker predictive of poor survival in those with PCNSL.

Stat3-positive tumor cells contribute to vessels neoformation in primary central nervous system lymphoma

With the aim of elucidating the relationship between Stat3 expression and tumor vessels abnormalities in the PCNLs, in this study we evaluated Stat3 and pStat3 expression by Real-time PCR and by immunohistochemistry in biopsy sections from PCNSL patients. Correlations of the expression levels with the presence of aberrant vessels were analyzed by confocal laser microscopy analysis, using FVIII as endothelial cell marker, CD133 and nestin as cancer stem cell (CSC) marker, CD20 as tumor cell marker, and Stat3. In addition, we investigated Stat3 mutations in lymphoma cells to clarify the role of the constitutive expression of Stat3 and of its phosphorylated forms. Results showed that in PCNSL, putative endothelial cells lining the vessels are heterogeneous, expressing FVIII/ pStat3/CD133 (presumably originally they are vascular progenitor cells), as well as FVIII/CD20/CD133 (presumably originally they are tumor cells). Finally, we detected a fraction of the FVIII⁺ endothelial cell that co-expressed Stat3 bearing a tetraploid karyotype, while no amplification signal for the Stat3 gene was detected.

STAT3 activation is associated with cerebrospinal fluid interleukin-10 (IL-10) in primary central nervous system diffuse large B cell lymphoma

Signal transducers and activators of transcription 3 (STAT3) are activated by various cytokines and oncogenes; however, the activity and pathogenesis of STAT3 in diffuse large B cell lymphoma of the central nervous system have not been thoroughly elucidated. We investigated the phosphorylation levels of STAT3 in 40 specimens of primary central nervous system diffuse large B-cell lymphoma (PCNS DLBCL) and analyzed the association between phsopho-STAT3 (pSTAT3) expression and cerebrospinal fluid (CSF) concentration of interleukin-10 (IL-10) or IL-6. Immunohistochemistry and Western blot analysis revealed that most of the specimens in PCNS DLBCL expressed pSTST3 protein, and a strong phosphorylation levels of STAT3 was statistically associated with high CSF IL-10 levels, but not with CSF IL-6 levels. Next, we demonstrated that recombinant IL-10 and CSF containing IL-10 induced the phosphorylation of STAT3 in PCNS DLBCL cells. Furthermore, molecular subtype classified by Hans' algorithm was correlated with pSTAT3 expression levels and CSF IL-10 levels. These results suggest that the STAT3 activity is correlated with CSF IL-10 level, which is a useful marker for STAT3 activity in PCNS DLBCLs.