Expression of p-AKT and p-mTOR in pediatric Burkitt lymphoma and their correlation with prognosis

Abstract

Objective: To evaluate the expression of p-AKT and p-mTOR, the key proteins in PI3K/AKT/mTOR pathway in pediatric Burkitt lymphoma (BL), and to investigate the clinical and prognostic significance. Methods: Fifty-eight cases of pediatric BL and thirty cases of reactive hyperplastic lymphadenitis (RH) were collected at Children's Hospital of Fudan University from September 2011 to July 2018. Paraffin sections of tissues were immune stained for p-AKT and p-mTOR, and the expression was assessed and correlated with the clinical features and prognosis. Results: A total of 58 cases were diagnosed and 6 cases lost the follow-up. Of the remaining 52 BL patients including 43 males and 9 females, the median age was 5 years (range: 2 to 14 years). Regarding to the correlation between the two biomarkers, Spearman test showed that p-mTOR was positively associated with the expression of p-AKT (r=0.759, P<0.001). Of all BL patients, the positive rates of p-AKT and p-mTOR were 62.1% (36/58) and 60.3%(35/58) respectively, both significantly higher than control group (P=0.011, P=0.035 respectively). The presence of p-AKT was significantly associated with higher lactate dehydrogenase (LDH≥573 IU/L) level in patients of the disease (P=0.006), while p-mTOR was increased both in the higher LDH and lower ratio of albumin to globulin (A/G) group (P=0.006, P=0.034 respectively). Expression of p-AKT and p-mTOR did not show any statistical correlation with sex, age, St.jude stage, tumor size, B-symptom present or not, number of extra-nodal sites or international prognostic index (IPI) (P>0.05). Fifty-two patients had a median follow-up of 40 months (range: 5-87 months). Univariate analysis showed that p-AKT expression was significant in predicting both inferior OS (5-year estimate, 72.7% vs. 94.7%, χ(2)=4.123, P=0.042) and PFS (5-year estimate, 66.7% vs. 94.7%, χ(2)=5.822, P=0.016). The 5-year OS rate was 71.0% (22/31) for the p-mTOR positive cohort of patients compared to 95.2% (17/21) for p-mTOR negative group (χ(2)=4.881, P=0.027); however, there was no statistical significance in 5-year PFS rate (P>0.05). Especially, the 5-year OS and PFS rate of p-AKT/p-mTOR double-positive group were significantly lower than negative control group (including absence of single p-AKT or p-mTOR expression, and absence of both) (OS: 69.0% vs. 95.7%, χ(2)=6.285, P=0.012; PFS: 65.5% vs. 91.3%, χ(2)=5.405, P=0.020). The results of multivariate COX proportional risk regression analysis indicated that p-AKT/p-mTOR double-positive, higher LDH and IPI score 3-5 were independent prognostic factors for both OS and PFS, and the bulky tumor (>10 cm) for PFS of pediatric BL. Conclusion: The expression of p-AKT and p-mTOR may be a potential reference for diagnosis and the independent prognostic indicators of pediatric BL.