Targeting quiescent leukemic stem cells using second generation autophagy inhibitors.

In chronic myeloid leukemia (CML), tyrosine kinase inhibitor (TKI) treatment induces autophagy that promotes survival and TKI-resistance in leukemic stem cells (LSCs). In clinical studies hydroxychloroquine (HCQ), the only clinically approved autophagy inhibitor, does not consistently inhibit autophagy in cancer patients, so more potent autophagy inhibitors are needed. We generated a murine model of CML in which autophagic flux can be measured in bone marrow-located LSCs. In parallel, we use cell division tracing, phenotyping of primary CML cells, and a robust xenotransplantation model of human CML, to investigate the effect of Lys05, a highly potent lysosomotropic agent, and PIK-III, a selective inhibitor of VPS34, on the survival and function of LSCs. We demonstrate that long-term haematopoietic stem cells (LT-HSCs: Lin-Sca-1+c-kit+CD48-CD150+) isolated from leukemic mice have higher basal autophagy levels compared with non-leukemic LT-HSCs and more mature leukemic cells. Additionally, we present that while HCQ is ineffective, Lys05-mediated autophagy inhibition reduces LSCs quiescence and drives myeloid cell expansion. Furthermore, Lys05 and PIK-III reduced the number of primary CML LSCs and target xenografted LSCs when used in combination with TKI treatment, providing a strong rationale for clinical use of second generation autophagy inhibitors as a novel treatment for CML patients with LSC persistence.

Targeting BCR-ABL-Independent TKI Resistance in Chronic Myeloid Leukemia by mTOR and Autophagy Inhibition.

Background: Imatinib and second-generation tyrosine kinase inhibitors (TKIs) nilotinib and dasatinib have statistically significantly improved the life expectancy of chronic myeloid leukemia (CML) patients; however, resistance to TKIs remains a major clinical challenge. Although ponatinib, a third-generation TKI, improves outcomes for patients with BCR-ABL-dependent mechanisms of resistance, including the T315I mutation, a proportion of patients may have or develop BCR-ABL-independent resistance and fail ponatinib treatment. By modeling ponatinib resistance and testing samples from these CML patients, it is hoped that an alternative drug target can be identified and inhibited with a novel compound. Methods: Two CML cell lines with acquired BCR-ABL-independent resistance were generated following culture in ponatinib. RNA sequencing and gene ontology (GO) enrichment were used to detect aberrant transcriptional response in ponatinib-resistant cells. A validated oncogene drug library was used to identify US Food and Drug Administration-approved drugs with activity against TKI-resistant cells. Validation was performed using bone marrow (BM)-derived cells from TKI-resistant patients (n = 4) and a human xenograft mouse model (n = 4-6 mice per group). All statistical tests were two-sided. Results: We show that ponatinib-resistant CML cells can acquire BCR-ABL-independent resistance mediated through alternative activation of mTOR. Following transcriptomic analysis and drug screening, we highlight mTOR inhibition as an alternative therapeutic approach in TKI-resistant CML cells. Additionally, we show that catalytic mTOR inhibitors induce autophagy and demonstrate that genetic or pharmacological inhibition of autophagy sensitizes ponatinib-resistant CML cells to death induced by mTOR inhibition in vitro (% number of colonies of control[SD], NVP-BEZ235 vs NVP-BEZ235+HCQ: 45.0[17.9]% vs 24.0[8.4]%, P = .002) and in vivo (median survival of NVP-BEZ235- vs NVP-BEZ235+HCQ-treated mice: 38.5 days vs 47.0 days, P = .04). Conclusion: Combined mTOR and autophagy inhibition may provide an attractive approach to target BCR-ABL-independent mechanism of resistance.

ATG7 regulates energy metabolism, differentiation and survival of Philadelphia-chromosome-positive cells.

A major drawback of tyrosine kinase inhibitor (TKI) treatment in chronic myeloid leukemia (CML) is that primitive CML cells are able to survive TKI-mediated BCR-ABL inhibition, leading to disease persistence in patients. Investigation of strategies aiming to inhibit alternative survival pathways in CML is therefore critical. We have previously shown that a nonspecific pharmacological inhibition of autophagy potentiates TKI-induced death in Philadelphia chromosome-positive cells. Here we provide further understanding of how specific and pharmacological autophagy inhibition affects nonmitochondrial and mitochondrial energy metabolism and reactive oxygen species (ROS)-mediated differentiation of CML cells and highlight ATG7 (a critical component of the LC3 conjugation system) as a potential specific therapeutic target. By combining extra- and intracellular steady state metabolite measurements by liquid chromatography-mass spectrometry with metabolic flux assays using labeled glucose and functional assays, we demonstrate that knockdown of ATG7 results in decreased glycolysis and increased flux of labeled carbons through the mitochondrial tricarboxylic acid cycle. This leads to increased oxidative phosphorylation and mitochondrial ROS accumulation. Furthermore, following ROS accumulation, CML cells, including primary CML CD34(+) progenitor cells, differentiate toward the erythroid lineage. Finally, ATG7 knockdown sensitizes CML progenitor cells to TKI-induced death, without affecting survival of normal cells, suggesting that specific inhibitors of ATG7 in combination with TKI would provide a novel therapeutic approach for CML patients exhibiting persistent disease.

The plastidic DNA replication enzyme complex of Plasmodium falciparum.

The replication and repair of organellar genomes in the malaria parasite Plasmodium falciparum is poorly understood. We have assessed the properties of an open reading frame Pfprex (formerly known as pom1) and confirm that it specifies a multi-domain polypeptide with DNA primase, DNA helicase, DNA polymerase and 3'-5' exonuclease activities. The sequence of the primase/helicase domain is phylogenetically related to the T7-bacteriophage gene 4 product and mammalian mitochondrial helicase, Twinkle. Despite that, the N-terminal sequence of this multi-domain polypeptide directs a green fluorescent protein reporter specifically to the P. falciparum apicoplast and not to the mitochondrion. Phylogenetic analysis placed the DNA polymerase sequence with the family A bacterial polymerases, most closely to those of the thermophilic Aquifex species. Notably, the malarial enzyme was optimally active at 75 degrees C. Pfprex is the first example of a gene encoding contiguous DNA polymerase, DNA primase and DNA helicase components. We propose it has a key role in replication of the malarial plastid genome, a validated drug target.

Can Postoperative Nutrition be Favourably Maintained by Oral Diet in Patients with Emergency Temporary Ileostomy? A Tertiary Hospital Based Study.

INTRODUCTION: Temporary ileostomy is an emergency procedure performed in cases having septic peritonitis in presence of perforation or obstruction or gangrene of small intestine. These patients usually suffer from gross malnutrition following surgery. AIM: To measure nutritional status of patients with emergency temporary ileostomy and to determine whether their postoperative nutrition can be favourably maintained by oral diet alone. MATERIALS AND METHODS: Sixty patients were enrolled for the study on the basis of inclusion and exclusion criteria during the study period from January 2012 to December 2013. Oral feeding was started as soon as ileostomy started functioning and patients expressed hunger, about 48-72 hours postoperatively. An individualized diet chart was formulated for each patient using Harris Benedict Equation. Nutritional assessment was done on 1) 1(st) day of oral feeding, 2) After 7 days of oral feeding, 3). After three months of oral feeding. Nutritional parameters (anthropometric, biochemical) employed were tabulated and statistically analysed with SPSS v 17, Chicago. RESULTS: Out of 60 patients, 36 males and 24 females were enrolled in the study. The patients were in the age group of 20-60 years with a mean age of 45 years. After 7 days of oral nutrition the nutritional status deteriorated with a significant decrease in body weight (p<0.001) and serum haemoglobin (p <0.001). However, at the end of the study, the patients had their nutritional status restored satisfactorily with normalization of basic parameters like bodyweight, haemoglobin and serum albumin (p<0.001). CONCLUSION: Proper dietary advice and oral nutrition were found to be sufficient for gradual restoration and maintenance of satisfactory nutritional status in the postoperative period.

Abdominal tuberculosis with an acute abdomen: our clinical experience.

INTRODUCTION: Tuberculosis is an important cause of morbidity in India. Abdominal Tuberculosis is a great mimicker and is difficult to diagnose. This prospective observational study is based on those patients who were diagnosed to be suffering from Abdominal Tuberculosis only after they presented with an acute abdomen. This study aims to document the nature of different types of acute presentation in Abdominal Tuberculosis according to involved sites and surgical pathology. The study also discusses the indications and extent of surgical intervention. MATERIALS AND METHODS: Seventy new cases of Abdominal Tuberculosis (out of 718 cases of acute abdomen) were diagnosed and treated over a period of three years in the surgical ward of Calcutta National Medical College. Macroscopic appearance of abdominal tissues during surgery suggested the diagnosis of tuberculosis. The diagnosis was confirmed by histopathology and tissue culture. All patients were subsequently treated with a full course of antitubercular drugs (ATD). RESULTS: The clinical presentations of acute abdomen included acute intestinal obstruction, perforative peritonitis and acute appendicitis etc. Terminal ileum and ileocaecal region were predominantly involved. The most common pathology was intestinal stricture with or without perforation. Most of the patients (approx 78.5%) required emergency surgery as a therapeutic intervention. A two-stage procedure was preferred in peritonitis and sepsis. Most of the remaining patients (12.8%) required surgery after initial conservative treatment for the first few days. Undiagnosed Abdominal Tuberculosis represents a notable percentage (10%) of patients who present with an acute abdomen as a surgical emergency. CONCLUSION: Abdominal Tuberculosis is very difficult to diagnose and diagnosis is often delayed till an acute abdomen is presented with. Almost all patients needed surgical intervention. Irrespective of surgery, all patients of abdominal tuberculosis require a full ATD.

Comparison of prophylactic and therapeutic immunisation with an ErbB-2 (HER2) fusion protein and immunoglobulin V-gene repertoire analysis in a transgenic mouse model of spontaneous breast cancer.

ErbB-2 is associated with several solid tumours of which breast cancer is the commonest cancer in women worldwide. Though anti-ErbB-2 antibody appears to play a significant role in prevention and therapy, naturally occurring anti-ErbB-2 antibody associated with the cleaved ectodomain of overexpressed ErbB-2 self antigen is detectable in patients. It is therefore essential to understand the course of antibody mediated protection during disease progression. 100% of FVB/N(neu) mice expressing mutated, constitutively active ErbB-2 develop mammary carcinoma. It has been shown that vaccination with ErbB-2 associated with a T helper cell epitope P30 can offer protection against transplantable tumour but it is unclear whether the same vaccine protects against naturally developing tumour. We have analysed the course of the disease following prophylactic, and therapeutic vaccination in this spontaneous, eutopic mammary carcinoma model that more closely resembles the human disease. 100% protection against tumour development was observed subsequent to prophylactic immunisation but disease progression was unaffected by therapeutic vaccination. The antibody response exhibited restricted expansion of the Immunoglobulin (Ig) variable (V)-gene repertoire by ErbB-2 specific B cells compared with the non-antigen specific B cell pool and control mice. The serum antibody profile was similar in therapeutically injected mice without any effect on tumour burden.

Autophagy in chronic myeloid leukaemia: stem cell survival and implication in therapy.

The insensitivity of Chronic Myeloid Leukaemia (CML) stem cells to Tyrosine Kinase Inhibitor (TKI) treatment is now believed to be the main reason for disease persistence experienced in patients. It has been shown that autophagy, an evolutionarily conserved catabolic process that involves degradation of unnecessary or harmful cellular components via lysosomes, is induced following TKI treatment in CML cells. Of clinical importance, autophagy inhibition, using the anti-malarial drug hydroxychloroquine (HCQ), sensitised CML cells, including primitive CML stem cells, to TKI treatment. In this review we discuss the role of autophagy in the maintenance and survival of stem cells in more detail, with a focus on its role in survival of CML stem cells and the possibility to inhibit this pathway as a way to eliminate persistent CML stem cells in vitro and in patients.

A NIMA-related protein kinase is essential for completion of the sexual cycle of malaria parasites.

The molecular mechanisms regulating the sexual development of malaria parasites from gametocytes to oocysts in their mosquito vector are still largely unexplored. In other eukaryotes, NIMA-related kinases (Neks) regulate cell cycle progression and have been implicated in the regulation of meiosis. Here, we demonstrate that Nek-4, a new Plasmodium member of the Nek family, is essential for completion of the sexual cycle of the parasite. Recombinant Plasmodium falciparum Nek-4 possesses protein kinase activity and displays substrate preferences similar to those of other Neks. Nek-4 is highly expressed in gametocytes, yet disruption of the nek-4 gene in the rodent malaria parasite P. berghei has no effect on gamete formation and subsequent fertilization. However, further differentiation of zygotes into ookinetes is abolished. Measurements of nuclear DNA content indicate that zygotes lacking Nek-4 fail to undergo the genome replication to the tetraploid level that precedes meiosis. Cell cycle progression in the zygote is identified as a likely precondition for its morphological transition to the ookinete and for the successful establishment of a malaria infection in the mosquito.