Akt Activation Confers an Inferior Survival in Patients with Activated B-Cell Subtype of Diffuse Large B-Cell Lymphoma: A Report from the International DLBCL Rituximab-CHOP Consortium Program

Context

Akt plays an essential role in diverse cellular processes such as cell proliferation, cell growth and apoptosis. Dysregulation of Akt signaling has been shown to correlate with an inferior survival in patients with a number of solid tumors and some hematologic malignances. The prognostic significance of Akt expression and the gene expression profile of Akt activation in diffuse large B-cell lymphoma (DLBCL) have not been thoroughly assessed.

Objective

In this study, we investigated Akt activation and analyzed its prognostic importance in a large cohort of patients with de novoDLBCL treated with R-CHOP immunochemotherapy. We also characterized the gene expression profile of DLBCL with activated Akt.

Patients

The study group consisted of 493 DLBCL patients treated with R-CHOP. These cases were organized as a part of the International DLBCL R-CHOP Consortium Program Study, and diagnosed according to the WHO criteria. Patients with primary mediastinal large B-cell lymphoma, primary cutaneous DLBCL, primary central nervous system DLBCL, and DLBCLs transformed from a low-grade B-cell lymphoma or associated with HIV infection were excluded.

Methods

Immunohistochemical studies (IHC) were performed in formalin-fixed paraffin-embedded sections of tissue microarrays to evaluate the expression of phosphorylated (activated) Akt and other relevant markers. Genetic alterations were examined by FISH for MYC, BCL-2, and BCL-6 translocations and sequencing for TP53 mutation. Gene expression profiling (GEP) was performed to characterize the gene expression profile in Akt-activated DLBCL. The cell-of-origin (COO) subtypes were determined by GEP (gold standard) and IHC.

Results

Phosphorylated (activated) Akt (pAkt) expression was detected in 98 of 493 (20%) DLBCL tumors including 49 of 253 (19%) GCB DLBCL and 49 of 240 (20%) ABC DLBCL. In the GCB subtype, MYC, BCL-2 and MYC/BCL-2 translocations were more frequently found in pAkt⁺ DLBCL compared with pAkt^- DLBCL (P=0.04, 0.007 and 0.03, respectively). In contrast, translocations of these genes were rare and detected equally in pAkt⁺ and pAkt^- subgroups within the ABC subtype (P=0.7, 0.9 and 0.9, respectively). In the GCB group, TP53 mutation frequency was similar between pAkt⁺ and pAkt^- DLBCL (P=0.45). In contrast, TP53 mutations were significantly less frequent in ABC group (5% versus 22%; P= 0.01). Akt activation predicted a poorer survival, but the negative prognostic impact of Akt activation was significant in the ABC (5-year survival rate: 44% in pAkt⁺ versus 65% in pAkt^-; P=0.01; 5-year PFS: 40% in pAkt⁺ versus 59% in pAkt^-; P=0.01), but not GCB subtype (5-year survival rate: 67% in pAkt⁺ versus 74% in pAkt^-, P=0.31; 5-year PFS rate: 61% in pAkt⁺ versus 69% in pAkt^-, P=0.27). The negative impact of Akt activation appeared to be independent of Myc/Bcl-2 expression and TP53 mutation. In multivariate analysis, pAkt expression was an independent predictor of poorer OS (HR=2.72, 95% CI, 1.50-4.98, P=0.001) and PFS (HR=2.16, 95% CI, 1.22-3.82, P=0.008) in patients with ABC wild type-TP53. In addition, AKT1 mRNA expression conferred significantly poor survival in DLBCL. Gene expression profiling revealed a distinct high-risk signature characterized by increased expression of multiple pro-survival genes (6 of 16 up-regulated genes; 40%) and decreased expression of genes encoding tumor suppressors (5 of 20 down-regulated genes; 25%) in pAkt⁺ ABC DLBCL.

Conclusions

Akt is activated in DLBCL, is equally distributed in COO subtypes, and has prognostic significance in patients with ABC DLBCL. Given the promising anti-lymphoma activity of Akt inhibitors in clinical trials, these findings may have clinical implications for DLBCL patients. Akt activation may be useful for prognostic stratification and could serve as a biomarker to guide patient selection and predict response to targeted anti-Akt therapy.