The bone marrow niche has a significant impact on acute lymphoblastic leukemia (ALL) cell phenotype. Of clinical relevance is the frequency with which quiescent leukemic cells, in this niche, survive treatment and contribute to relapse. This study suggests that marrow microenvironment regulation of BCL6 in ALL is one factor that may be involved in the transition between proliferative and quiescent states of ALL cells. Utilizing ALL cell lines, and primary patient tumor cells we observed that tumor cell BCL6 protein abundance is decreased in the presence of primary human bone marrow stromal cells (BMSC) and osteoblasts (HOB). Chemical inhibition, or shRNA knockdown, of BCL6 in ALL cells resulted in diminished ALL proliferation. As many chemotherapy regimens require tumor cell proliferation for optimal efficacy, we investigated the consequences of constitutive BCL6 expression in leukemic cells during co-culture with BMSC or HOB. Forced chronic expression of BCL6 during co-culture with BMSC or HOB sensitized the tumor to chemotherapy induced cell death. Combination treatment of caffeine, which increases BCL6 expression in ALL cells, with chemotherapy extended the event free survival of mice. These data suggest that BCL6 is one factor, modulated by microenvironment derived cues that may contribute to regulation of ALL therapeutic response.

Mesenchymal stem cells (MSCs) are of interest for use in diverse cellular therapies. Ex vivo expansion of MSCs intended for transplantation must result in generation of cells that maintain fidelity of critical functions. Previous investigations have identified genetic and phenotypic alterations of MSCs with in vitro passage, but little is known regarding how culturing influences the ability of MSCs to repair double strand DNA breaks (DSBs), the most severe of DNA lesions. To investigate the response to DSB stress with passage in vitro, primary human MSCs were exposed to etoposide (VP16) at various passages with subsequent evaluation of cellular damage responses and DNA repair. Passage number did not affect susceptibility to VP16 or the incidence and repair kinetics of DSBs. Nonhomologous end joining (NHEJ) transcripts showed little alteration with VP16 exposure or passage; however, homologous recombination (HR) transcripts were reduced following VP16 exposure with this decrease amplified as MSCs were passaged in vitro. Functional evaluations of NHEJ and HR showed that MSCs were unable to activate NHEJ repair following VP16 stress in cells after successive passage. These results indicate that ex vivo expansion of MSCs alters their ability to perform DSB repair, a necessary function for cells intended for transplantation.

Osteoblasts are a major component of the bone marrow microenvironment which provide support for hematopoietic cell development. Functional disruption of any element of the bone marrow niche, including osteoblasts, can potentially impair hematopoiesis. We have studied the effect of two widely used drugs with different mechanisms of action, etoposide (VP16) and melphalan, on murine osteoblasts at distinct stages of maturation. VP16 and melphalan delayed maturation of preosteoblasts and altered CXCL12 protein levels, a key regulator of hematopoietic cell homing to the bone marrow. Sublethal concentrations of VP16 and melphalan also decreased the levels of several transcripts which contribute to the composition of the extracellular matrix (ECM) including osteopontin (OPN), osteocalcin (OCN) and collagen 1A1 (Col1a1). The impact of chemotherapy on message and protein levels for some targets was not always aligned, suggesting differential responses at the transcription and translation or protein stability levels. Since one of the main functions of a mature osteoblast is to synthesize ECM of a defined composition, disruption of the ratio of its components may be one mechanism by which chemotherapy affects the ability of osteoblasts to support hematopoietic recovery coincident with altered marrow architecture. Collectively, these observations suggest that the osteoblast compartment of the marrow hematopoietic niche is vulnerable to functional dysregulation by damage imposed by agents frequently used in clinical settings. Understanding the mechanistic underpinning of chemotherapy-induced changes on the hematopoietic support capacity of the marrow microenvironment may contribute to improved strategies to optimize patient recovery post-transplantation.

Background: Home enteral nutrition (HEN) is frequently prescribed to individuals who cannot consume adequate food orally. Commercial blenderized enteral formulas (CBEF) containing real-food ingredients are becoming more popular and more widely available; however, the demographics of patients receiving these formulas have rarely been evaluated, and little data are available on patient tolerance in the community. Methods: US claims data were obtained for children and adolescents/adults who used the CBEF of interest as the sole source of nutrition via enteral feeding tube in the community setting following discharge from acute care. Demographics, concomitant medications, clinical diagnoses, and Charlson Comorbidity Index scores were tabulated using descriptive statistics. Gastrointestinal (GI) symptoms before and after hospital discharge were compared using significance tests. Results:The study included 231 participants (180 children, 51 adolescents/ adults). CBEFs were prescribed to patients with a variety of diagnoses, of which the most common were digestive and respiratory disorders. Children experienced significantly lower rates of diarrhea, nausea, vomiting, constipation, and abdominal distension in the weeks following hospital discharge compared with the baseline (all P < 0.001). Adolescents/adults experienced significantly lower rates of constipation, nausea, and vomiting (all P < 0.05).Neither group increased their usage of GI medications following hospital discharge. Conclusion:These CBEFs, based on real-food ingredients, were prescribed to diverse patients in the community and were well tolerated. These formulas offer an alternative to standard polymeric formulas and an alternative or adjunct to homemade blenderized formulas.

This thesis introduces and defends a new hypothesis concerning autism:Semantic Feature Dissociation (SFD). The claim is that some autistic people only store information about strong correlations in semantic memory. I begin by arguing the most promising theories of autism currently on offer are Bayesian theories. However, these omit important details, especially about the underlying format of world knowledge, and its role in social cognition. The SFD hypothesis bridges this gap, linking autism traits explicitly to research on concept structure.After critically reviewing key literature, I defend the hypothesis in two ways.First, I report a methodologically novel qualitative study of autism autobiographies, from which the hypothesis was abducted. This reveals that it can potentially account for many real-world autism traits. Crucially, most social and language differences can be attributed to general changes in the structure of world knowledge, without implicating a specialised mechanism for identifying mental states. Second, I show SFD is better than other accounts at predicting important lines of experimental evidence concerning social cognition, language and perception in autism. I conclude by tentatively suggesting SFD might reconcile the two leading Bayesian accounts of autism: HIPPEA and weak priors.3