Effective use of small-interfering RNA to characterize residual B-cell non-Hodgkin lymphoma cells following chemotherapy.

BACKGROUND: Children diagnosed with non-Hodgkin lymphoma (NHL) respond well to therapy resulting in relatively good prognosis. The exceptions are those who continue to have minimal residual disease (MRD). MRD NHL cells have been characterized as having increased mitochondrial DNA (mtDNA) copy numbers with increased expression of citrate synthase and isocitrate dehydrogenase. A proof-of-concept was designed to use small-interfering RNA (siRNA) as a tool to elucidate the relationship between citrate synthase and isocitrate dehydrogenase with cancer cell integrity. METHODS: mtDNA copy number and lactate dehydrogenase activities were assessed in chemotherapy-exposed residual NHL cells after introduction of siRNA against citrate synthase and/or isocitrate dehydrogenase expression. RESULTS: There was a significant decrease in lactate production in cells transfected with citrate synthase siRNA (p=0.02). Citrate synthase-silenced cells had decreased mtDNA copy numbers (p=0.03) compared to isocitrate dehydrogenase-silenced cells or combined citrate synthase- and isocitrate dehydrogenase-silenced cells. CONCLUSION: Inhibition of citrate synthase expression in siRNA-treated NHL cells resulted in decreased mtDNA copy numbers and lactate dehydrogenase expression. This observation needs further validation to determine the role of citrate synthase in mtDNA integrity and if citrate synthase siRNA could be a potential therapeutic modality in eradicating residual B-NHL cells.

Cognitive performance related to HIV-1-infected monocytes.

The effect that HIV type 1 (HIV) has on neurocognition is a dynamic process whereby peripheral events are likely involved in setting the stage for clinical findings. In spite of antiretroviral therapy (ART), patients continue to be at risk for HIV-associated neurocognitive disorders (HAND), which might be related to persistence of inflammation. In a yearly assessment of HIV DNA levels in activated monocytes, increased HIV DNA copies were found in patients with persistent HAND. Furthermore, activated monocytes from patients with high HIV DNA copies secreted more inflammatory cytokines. Since these activated monocytes traffic to the CNS and enter the brain, they may contribute to an inflammatory environment in the CNS that leads to HAND.

Minimal disease assessment in the treatment of children and adolescents with intermediate-risk (Stage III/IV) B-cell non-Hodgkin lymphoma: a children's oncology group report.

Children/adolescents with mature B-cell non-Hodgkin lymphoma (B-NHL) have an excellent prognosis but relapses still occur. While chromosomal aberrations and/or clonal immunoglobulin (Ig) gene rearrangements may indicate risk of failure, a more universal approach was developed to detect minimal disease (MD). Children/adolescents with intermediate-risk B-NHL were treated with French-British-American/Lymphome Malins de Burkitt 96 (FAB/LMB96) B4 modified chemotherapy and rituximab. Specimens from diagnosis, end of induction (EOI), and end of therapy (EOT) were assayed for MD. Initial specimens were screened for IGHV family usage with primer pools followed by individual primers to identify MD. Thirty-two diagnostic/staging specimens screened positive with primer pools and unique IGHV family primers were identified. Two patients relapsed; first relapse (4 months from diagnosis) was MD-positive at EOI, the second (36 months from diagnosis) was MD-positive at EOT. At EOI, recurrent rates were similar between the MRD-positive and MRD-negative patients (P = 0·40). At EOT, only 13/32 patients had MRD data available with one relapse in the MRD-positive group and no recurrences in the MRD-negative group (P = 0·077). The study demonstrated molecular-disseminated disease in which IgIGHV primer pools could be used to assess MD. This feasibility study supports future investigations to assess the validity and significance of MD screening in a larger cohort of patients with intermediate-risk mature B-NHL.

Mitochondrial DNA in residual leukemia cells in cerebrospinal fluid in children with acute lymphoblastic leukemia.

UNLABELLED: This feasibility study was designed to assess the ability to measure mitochondrial DNA (mtDNA) in cerebrospinal fluid (CSF) cells that contributed to minimal disease/persistent or residual disease (MD/PRD) from children with acute lymphoblastic leukemia (ALL). Increase in mtDNA copies in cancer cells has been suggested to play a role in MD/PRD. CSF as well as blood specimens from 6 children were assayed for MD/PRD and mtDNA copy numbers by quantitative real-time polymerase chain reaction. Of 7 MD/PRD-positive specimens, 6 had increased mtDNA copy numbers; while 11 MD/PRD-negative specimens had no increase in mtDNA copy numbers, p < 0.003. This is the first proof-of-concept study to measure mtDNA copy numbers in MD/PRD-positive CSF specimens from children with ALL. Increase of mtDNA copy numbers in MD/PRD childhood ALL cells and its significance as a mechanism for recurrence requires further investigation. KEYWORDS: Minimal residual disease; Acute lymphoblastic leukemia; Central nervous system; Cerebrospinal fluid; Mitochondria.

Screening for residual disease in pediatric burkitt lymphoma using consensus primer pools.

Assessing molecular persistent or minimal residual disease (PD/MRD) in childhood Burkitt lymphoma (BL) is challenging because access to original tumor is usually needed to design patient-specific primers (PSPs). Because BL is characterized by rearranged immunoglobulin heavy chain (IgV(H)) genes, IgV(H) primer pools from IgV(H1)-IgV(H7) regions were tested to detect PD/MRD, thus eliminating the need for original tumor. The focus of the current study was to assess the feasibility of using IgV(H) primer pools to detect disease in clinical specimens. Fourteen children diagnosed with B-NHL had follow-up repository specimens available to assess PD/MRD. Of the 14 patients, 12 were PD/MRD negative after 2 months of therapy and remained in remission at the end of therapy; 2/14 patients were PD/MRD positive at 2-3 months and later relapsed. PSP-based assays from these 14 patients showed 100% concordance with the current assay. This feasibility study warrants further investigation to assess PD/MRD using IgV(H) primer pools, which could have clinical significance as a real-time assessment tool to monitor pediatric BL and possibly other B-cell non-Hodgkin lymphoma therapy.

Chemotoxicity recovery of mitochondria in non-Hodgkin lymphoma resulting in minimal residual disease.

BACKGROUND: The mechanisms responsible for resistant disease or recurrence of non-Hodgkin lymphoma (NHL) in children cover a wide spectrum from drug resistance to genetic mutations. A unique mechanism suggesting the role of mitochondria as the key energy source is studied following a clinical observation where pediatric Burkitt lymphoma (BL) specimens from patients on therapy were found to have increased copies of mitochondria DNA (mtDNA) in specimens which were shown to be positive for minimal residual disease and/or persistent disease (MRD/PD). This study hypothesized that the mitochondria play an important role in a cell's recovery from toxicity via a compensatory increase in mtDNA. PROCEDURE: BL specimens with MRD/PD were assayed for mtDNA. An in vitro model was then designed using Ramos cell lines by exposing the lymphoma cells to varying concentrations of doxorubicin and vincristine for 1 hr; and allowing for recovery in culture over 7 days. DNA was extracted from aliquots over several days to determine mtDNA copy numbers by real-time polymerase chain reaction (PCR). RESULTS: Increased mtDNA copy numbers were found in clinical specimens with MRD/PD as well as in recovering Ramos cells from chemotoxicity. CONCLUSIONS: The recovering lymphoma cells from the chemotoxic effects appeared to compensate by increasing mtDNA content, which may contribute to the clinical residual or resistant disease in some cases of childhood BL.

Possible Mitochondria-Associated Enzymatic Role in Non-Hodgkin Lymphoma Residual Disease.

BACKGROUND: The mechanisms responsible for resistant or recurrent disease in childhood non-Hodgkin lymphoma (NHL) are not yet fully understood. A unique mechanism suggesting the role of the mitochondria as the key energy source responsible for residual cells has been assessed in the clinical setting on specimens from patients on therapy were found to have increased copies of mitochondrial DNA (mtDNA) associated with positive minimal residual disease and/or persistent disease (MRD/PD) status. The potential role of mtDNA in MRD/PD emphasizes queries into the contributions of relevant enzymatic pathways responsible for MRD/PD. This study hypothesized that in an in-vitro model, recovering or residual cells from chemotoxicity will exhibit an increase in both citrate synthase and isocitrate dehydrogenase expression and decrease in succinate dehydrogenase expression. PROCEDURE: Ramos cells (Burkitt lymphoma cell line) were exposed to varying concentrations of doxorubicin and vincristine for 1 hr; and allowing for recovery in culture over a 7-day period. cDNA was extracted on days 1 and 7 of the cell culture period to assess the relative expression of the aforementioned genes. RESULTS: Increase citrate synthase, increase isocitrate dehydrogenase and decrease succinate dehydrogenase expressions were found in recovering Ramos cells. CONCLUSION: Recovering lymphoma cells appear to compensate by regulating enzymatic levels of appropriate genes in the Krebs Cycle suggesting an important role of the mitochondria in the presence of residual cells.