Comprehensive mutational analysis of primary and relapse acute promyelocytic leukemia.

Acute promyelocytic leukemia (APL) is a subtype of myeloid leukemia characterized by differentiation block at the promyelocyte stage. Besides the presence of chromosomal rearrangement t(15;17), leading to the formation of PML-RARA (promyelocytic leukemia-retinoic acid receptor alpha) fusion, other genetic alterations have also been implicated in APL. Here, we performed comprehensive mutational analysis of primary and relapse APL to identify somatic alterations, which cooperate with PML-RARA in the pathogenesis of APL. We explored the mutational landscape using whole-exome (n=12) and subsequent targeted sequencing of 398 genes in 153 primary and 69 relapse APL. Both primary and relapse APL harbored an average of eight non-silent somatic mutations per exome. We observed recurrent alterations of FLT3, WT1, NRAS and KRAS in the newly diagnosed APL, whereas mutations in other genes commonly mutated in myeloid leukemia were rarely detected. The molecular signature of APL relapse was characterized by emergence of frequent mutations in PML and RARA genes. Our sequencing data also demonstrates incidence of loss-of-function mutations in previously unidentified genes, ARID1B and ARID1A, both of which encode for key components of the SWI/SNF complex. We show that knockdown of ARID1B in APL cell line, NB4, results in large-scale activation of gene expression and reduced in vitro differentiation potential.

A hospital-based study of splenomegaly with special reference to the group of indeterminate origin.

In any study there remains a proportion of cases, about 25-40%, where cause of splenomegaly is not identified on usual evaluation, that is labelled as indeterminate group. The aim of this study was to evaluate various causes of splenomegaly. Thereafter the patients with splenomegaly of indeterminate origin were to be re-evaluated with detailed investigations (for the cause of splenomegaly). Causes of splenomegaly were looked into 100 adult patients with splenomegaly, admitted over a period of ten months in a teaching hospital in South India. Patients having ascites were excluded from the study. Malaria was the commonest cause of splenomegaly, observed in 22 patients. Other causes, in order of importance, were chronic myeloid leukaemia (n=11), non-cirrhotic portal fibrosis (n=9), enteric fever (n=9), cirrhosis of liver (n=8) and hyper-reactive malarial splenomegaly also called as tropical splenomegaly syndrome (n=7) and so on. Hyper-reactive malarial splenomegaly was the commonest cause (7 of 24 patients) of massive splenomegaly. Twenty-three patients had splenomegaly of indeterminate origin ie, cause could not be detected on first assessment. Detailed re-evaluation with repeat investigations including liver biopsy revealed the causes as follows: Hyper-reactive malarial splenomegaly -7 (30.4%), non-cirrhotic portal fibrosis - 4 (17.4%), cirrhosis of liver - 4 (17.4%) and iron deficiency anaemia - 5 (21.7%). In 3 patients (13.0%), no diagnosis could be arrived at despite best efforts. Obscure splenomegalies may be due to conditions like hyper-reactive malarial splenomegaly, non-cirrhotic portal fibrosis, iron deficiency anaemia, and even cirrhosis of liver, while malaria is still the most important cause of splenomegaly in India. Whereas the overall incidence of hyper-reactive malarial splenomegaly was only 7% in this study, it stood as the leading cause (29.2%), when analysed among patients with massive splenomegaly. Liver biopsy should be performed in all cases of obscure splenomegaly to arrive at the final diagnosis.