Muhamed Baljevic

CD133 expression is not restricted to stem cells, and both CD133+ and CD133– metastatic colon cancer cells initiate tumors

Colon cancer stem cells are believed to originate from a rare population of putative CD133+ intestinal stem cells. Recent publications suggest that a small subset of colon cancer cells expresses CD133, and that only these CD133+ cancer cells are capable of tumor initiation. However, the precise contribution of CD133+ tumor-initiating cells in mediating colon cancer metastasis remains unknown. Therefore, to temporally and spatially track the expression of CD133 in adult mice and during tumorigenesis, we generated a knockin lacZ reporter mouse (CD133lacZ/+), in which the expression of lacZ is driven by the endogenous CD133 promoters. Using this model and immunostaining, we discovered that CD133 expression in colon is not restricted to stem cells; on the contrary, CD133 is ubiquitously expressed on differentiated colonic epithelium in both adult mice and humans. Using Il10-/-CD133lacZ mice, in which chronic inflammation in colon leads to adenocarcinomas, we demonstrated that CD133 is expressed on a full gamut of colonic tumor cells, which express epithelial cell adhesion molecule (EpCAM). Similarly, CD133 is widely expressed by human primary colon cancer epithelial cells, whereas the CD133- population is composed mostly of stromal and inflammatory cells. Conversely, CD133 expression does not identify the entire population of epithelial and tumor-initiating cells in human metastatic colon cancer. Indeed, both CD133+ and CD133- metastatic tumor subpopulations formed colonospheres in in vitro cultures and were capable of long-term tumorigenesis in a NOD/SCID serial xenotransplantation model. Moreover, metastatic CD133- cells form more aggressive tumors and express typical phenotypic markers of cancer-initiating cells, including CD44 (CD44+CD24-), whereas the CD133+ fraction is composed of CD44lowCD24+ cells. Collectively, our data suggest that CD133 expression is not restricted to intestinal stem or cancer-initiating cells, and during the metastatic transition, CD133+ tumor cells might give rise to the more aggressive CD133(- )subset, which is also capable of tumor initiation in NOD/SCID mice.

Slitrk5 deficiency impairs corticostriatal circuitry and leads to obsessive-compulsive-like behaviors in mice

Obsessive-compulsive disorder (OCD) is a common psychiatric disorder defined by the presence of obsessive thoughts and repetitive compulsive actions, and it often encompasses anxiety and depressive symptoms. Recently, the corticostriatal circuitry has been implicated in the pathogenesis of OCD. However, the etiology, pathophysiology and molecular basis of OCD remain unknown. Several studies indicate that the pathogenesis of OCD has a genetic component. Here we demonstrate that loss of a neuron-specific transmembrane protein, SLIT and NTRK-like protein-5 (Slitrk5), leads to OCD-like behaviors in mice, which manifests as excessive self-grooming and increased anxiety-like behaviors, and is alleviated by the selective serotonin reuptake inhibitor fluoxetine. Slitrk5−/− mice show selective overactivation of the orbitofrontal cortex, abnormalities in striatal anatomy and cell morphology and alterations in glutamate receptor composition, which contribute to deficient corticostriatal neurotransmission. Thus, our studies identify Slitrk5 as an essential molecule at corticostriatal synapses and provide a new mouse model of OCD-like behaviors.

Mutational Cooperativity Linked to Combinatorial Epigenetic Gain of Function in Acute Myeloid Leukemia

Specific combinations of acute myeloid leukemia (AML) disease alleles, including FLT3 and TET2 mutations, confer distinct biologic features and adverse outcome. We generated mice with mutations in Tet2 and Flt3, which resulted in fully penetrant, lethal AML. Multipotent Tet2(-/-);Flt3(ITD) progenitors (LSK CD48(+)CD150(-)) propagate disease in secondary recipients and were refractory to standard AML chemotherapy and FLT3-targeted therapy. Flt3(ITD) mutations and Tet2 loss cooperatively remodeled DNA methylation and gene expression to an extent not seen with either mutant allele alone, including at the Gata2 locus. Re-expression of Gata2 induced differentiation in AML stem cells and attenuated leukemogenesis. TET2 and FLT3 mutations cooperatively induce AML, with a defined leukemia stem cell population characterized by site-specific changes in DNA methylation and gene expression.

Angiomodulin Is a Specific Marker of Vasculature and Regulates Vascular Endothelial Growth Factor-A–Dependent Neoangiogenesis

Blood vessel formation is controlled by the balance between pro- and antiangiogenic pathways. Although much is known about the factors that drive sprouting of neovessels, the factors that stabilize and pattern neovessels are undefined. The expression of angiomodulin (AGM), a vascular endothelial growth factor (VEGF)-A binding protein, was increased in the vasculature of several human tumors as compared to normal tissue, raising the hypothesis that AGM may modulate VEGF-A–dependent vascular patterning. To elucidate the expression pattern of AGM, we developed an AGM knockin reporter mouse (AGMlacZ/+), with which we demonstrate that AGM is predominantly expressed in the vasculature of developing embryos and adult organs. During physiological and pathological angiogenesis, AGM is upregulated in the angiogenic vasculature. Using the zebrafish model, we found that AGM is restricted to developing vasculature by 17 to 22 hours postfertilization. Blockade of AGM activity with morpholino oligomers results in prominent angiogenesis defects in vascular sprouting and remodeling. Concurrent knockdown of both AGM and VEGF-A results in synergistic angiogenesis defects. When VEGF-A is overexpressed, the compensatory induction of the VEGF-A receptor, VEGFR2/flk-1, is blocked by the simultaneous injection of AGM morpholino oligomers. These results demonstrate that the vascular-specific marker AGM modulates vascular remodeling in part by temporizing the proangiogenic effects of VEGF-A.

Curing All Patients with Acute Promyelocytic Leukemia: Are We There Yet?

The introduction of all-trans retinoic acid to anthracycline-based chemotherapy has revolutionized the prognosis of patients with acute promyelocytic leukemia (APL). The introduction of arsenic trioxide enabled the therapeutic approach of rationally targeted frontline protocols with minimal or no traditional cytotoxic chemotherapy and without compromise of previously established outstanding outcomes with anthracycline-based regimens. Although most of the current investigative efforts in APL are focused on developing potentially curative therapy without the exposure to toxicities and risks of DNA-disrupting agents, the cure rate can further be increased by implementing meticulous supportive care strategies that counter early coagulopathy-related deaths.

Epstein-barr virus-related hemophagocytic lymphohistiocytosis: hematologic emergency in the critical care setting.

Hemophagocytic lymphohistiocytosis (HLH) is a rare and potential life-threatening clinical syndrome that results from uncontrolled activation of the immune system. Secondary HLH, more commonly observed in adult patients, is seen in the context of underlying triggering conditions. Epstein-Barr virus (EBV) has been recognized as the leading infectious cause and is associated with a poor outcome. As clinical and laboratory features of HLH could overlap with septic shock syndrome in most patients, the diagnosis of HLH, especially in adults, is the most challenging aspect of the disease that results in delayed recognition and treatment of rapidly progressive multiorgan system failure. We report a case of Hemophagocytic lymphohistiocytosis in a patient who presented with signs of septic shock syndrome and we review the literature on the topic.

Telomere Length Recovery: A Strong Predictor of Overall Survival in Acute Promyelocytic Leukemia

Telomeres are the capping ends of chromosomes that protect the loss of genetic material and prevent chromosomal instability. In human tissue-specific stem/progenitor cells, telomere length (TL) is maintained by the telomerase complex, which consists of a reverse transcriptase catalytic subunit (TERT) and an RNA template (TERC). Very short telomeres and loss-of-function mutations in the TERT and TERC genes have been reported in acute myeloid leukemia, but the role of telomeres in acute promyelocytic leukemia (APL) has not been well established. We report the results for a large cohort of 187 PML/RARα-positive APL patients. No germline mutations in the TERT or TERC genes were identified. Codon 279 and 1062 TERT polymorphisms were present at a frequency similar to that in the general population. TL measured in blood or marrow mononuclear cells at diagnosis was significantly shorter in the APL patients than in healthy volunteers, and shorter telomeres at diagnosis were significantly associated with high-risk disease. For patients who achieved complete remission, the median increase in TL from diagnosis to remission (delta TL) was 2.0 kilobase (kb), and we found delta TL to be the most powerful predictor of overall survival when compared with well-established risk factors for poor outcomes in APL.

Ethics of medical care for body packers (drug smugglers): untangling a web of fears and conflicts of interest.

Body packing by drug smugglers--the transport of illicit drugs in packets swallowed or inserted into body cavities--is a global phenomenon and is becoming more prevalent. The medical care of these patients raises difficult medical and ethical problems. While the medical aspects of treating body packers have been systematically analysed, the ethical issues have received little attention in the literature. The patient may be under police custody or being sought by their criminal patron which may result in imposed interrogations and risky medical procedures. Obtaining informed valid consent for procedures from the patient-detainee may thus be compromised. In addition, physicians may be intimidated by the patients criminal contacts. This article analyses the conflicts of interest that doctors may face when treating body packers, and proposes some principles to promote institutional guidelines for the treatment of these patients.

Translocation t(11;17) in de novo Myelodysplastic Syndrome Not Associated with Acute Myeloid or Acute Promyelocytic Leukemia

Translocation t(11;17) is a well-recognized variant of acute promyelocytic leukemia (APL) and has also been identified in patients with mixed-lineage leukemia (MLL) non-APL acute myeloid leukemia. Here, we describe two patients bearing translocation t(11;17) presenting with a clinical diagnosis of de novo myelodysplastic syndrome (MDS): the first with sole karyotypic abnormality 46,XY,t(11;17)(p11.2; p13) and the second where it represented one of the two karyotypic abnormalities 46,XX,del(5)(q13q33)46,XX,del(5)(q13q33),t(11;17)(q24;q23). Molecular characterization of both cases failed to identify fusion transcripts involving MLL or PLZF-RARA and no collaborating somatic mutations commonly found among MDS patients were seen in either case, suggesting the presence of an as yet unidentified oncogenic fusion protein.