Lamellipodin-Deficient Mice: A Model of Rectal Carcinoma

During a survey of clinical rectal prolapse (RP) cases in the mouse population at MIT animal research facilities, a high incidence of RP in the lamellipodin knock-out strain, C57BL/6-Raph1[superscript tm1Fbg] (Lpd[superscript -/-]) was documented. Upon further investigation, the Lpd[superscript -/-] colony was found to be infected with multiple endemic enterohepatic Helicobacter species (EHS). Lpd[superscript -/-] mice, a transgenic mouse strain produced at MIT, have not previously shown a distinct immune phenotype and are not highly susceptible to other opportunistic infections. Predominantly male Lpd[superscript -/-] mice with RP exhibited lesions consistent with invasive rectal carcinoma concomitant to clinically evident RP. Multiple inflammatory cytokines, CD11b+Gr1+ myeloid-derived suppressor cell (MDSC) populations, and epithelial cells positive for a DNA damage biomarker, H2AX, were elevated in affected tissue, supporting their role in the neoplastic process. An evaluation of Lpd[superscript -/-] mice with RP compared to EHS-infected, but clinically normal (CN) Lpd[superscript -/-] animals indicated that all of these mice exhibit some degree of lower bowel inflammation; however, mice with prolapses had significantly higher degree of focal lesions at the colo-rectal junction. When Helicobacter spp. infections were eliminated in Lpd[superscript -/-] mice by embryo transfer rederivation, the disease phenotype was abrogated, implicating EHS as a contributing factor in the development of rectal carcinoma. Here we describe lesions in Lpd[superscript -/-] male mice consistent with a focal inflammation-induced neoplastic transformation and propose this strain as a mouse model of rectal carcinoma.United States. National Institutes of Health (T32-OD010978)United States. National Institutes of Health (R01-OD011141)United States. National Institutes of Health (P30-ES002109)Massachusetts Institute of Technology. Ludwig Center for Molecular Oncology (U54- CA114462)National Cancer Institute (U.S.) (P30-CA14051

Bone Marrow Myeloid Cells Regulate Myeloid-Biased Hematopoietic Stem Cells via a Histamine-Dependent Feedback Loop

Myeloid-biased hematopoietic stem cells (MB-HSCs) play critical roles in recovery from injury, but little is known about how they are regulated within the bone marrow niche. Here we describe an auto-/paracrine physiologic circuit that controls quiescence of MB-HSCs and hematopoietic progenitors marked by histidine decarboxylase (Hdc). Committed Hdc+ myeloid cells lie in close anatomical proximity to MB-HSCs and produce histamine, which activates the H2 receptor on MB-HSCs to promote their quiescence and self-renewal. Depleting histamine-producing cells enforces cell cycle entry, induces loss of serial transplant capacity, and sensitizes animals to chemotherapeutic injury. Increasing demand for myeloid cells via lipopolysaccharide (LPS) treatment specifically recruits MB-HSCs and progenitors into the cell cycle; cycling MB-HSCs fail to revert into quiescence in the absence of histamine feedback, leading to their depletion, while an H2 agonist protects MB-HSCs from depletion after sepsis. Thus, histamine couples lineage-specific physiological demands to intrinsically primed MB-HSCs to enforce homeostasis. Chen et al. show that histidine decarboxylase (Hdc) marks quiescent myeloid-biased HSCs (MB-HSCs). Daughter myeloid cells form a spatial cluster with Hdc+ MB-HSCs and secrete histamine to enforce their quiescence and protect them from depletion, following activation by a variety of physiologic insults

Dclk1 Defines Quiescent Pancreatic Progenitors that Promote Injury-Induced Regeneration and Tumorigenesis

The existence of adult pancreatic progenitor cells has been debated. While some favor the concept of facultative progenitors involved in homeostasis and repair, neither a location nor markers for such cells have been defined. Using genetic lineage tracing, we show that Doublecortin-like kinase-1 (Dclk1) labels a rare population of long-lived, quiescent pancreatic cells. In vitro, Dclk1+ cells proliferate readily and sustain pancreatic organoid growth. In vivo, Dclk1+ cells are necessary for pancreatic regeneration following injury and chronic inflammation. Accordingly, their loss has detrimental effects after cerulein-induced pancreatitis. Expression of mutant Kras in Dclk1+ cells does not affect their quiescence or longevity. However, experimental pancreatitis converts Kras mutant Dclk1+ cells into potent cancer-initiating cells. As a potential effector of Kras, Dclk1 contributes functionally to the pathogenesis of pancreatic cancer. Taken together, these observations indicate that Dclk1 marks quiescent pancreatic progenitors that are candidates for the origin of pancreatic cancer

The potential risk of tumor progression after use of dehydrated human amnion/chorion membrane allograft in a positive margin resection model

Objective: The objective of this study was to examine the impact of dehydrated human amnion/chorion membrane (dHACM) allografts on prostate and bladder cancer growth in the setting of residual disease and positive surgical margins. Materials and methods: A commercially available version of dHACM was used. Cytokines were identified and quantified, followed by comparative analysis of cell growth in two different human cell lines: prostate cancer (LNCaP) and bladder cancer (UM-UC-3), in vitro and in vivo. Tumor growth between the two groups, membrane versus no membrane implant, was compared and immunohistochemistry studies were conducted to quantify CD-31, Ki-67, and vimentin. A Student’s unpaired t -test was used to determine statistical significance. Results: The UM-UC-3 and LNCaP cells grew quicker in medium plus 10% serum and dHACM extract than in the other media ( p = 0.03). A total of 28 distinct cytokines were found in the extract, 11 of which had relatively high concentrations and are associated with prostate and bladder cancer tumor progression. In vivo LNCaP model, after 10 weeks, the median tumor volume in the membrane group was almost threefold larger than the partial resection alone ( p = 0.01). Two weeks after resection, in the UM-UC-3 model, the membrane group reached fourfold larger than the partial resection without membrane group ( p 0.05). It was only in the LNCaP tumors that vimentin expression was significantly higher in the group without membrane compared with the membrane group ( p = 0.008). Conclusion: The use of dHACM after partial tumor resection is related to faster tumor relapse and growth in prostate and urothelial cancer in vivo models, showing a potential risk of rapid local recurrence in patients at high risk of positive margins

Immunostaining and morphologic analysis of DNA damage using H2AX.

<p>(A) immunostaining of DNA damage marker H2AX in LPD -/- mice without EHS infection, LPD -/- mice with EHS infection and with rectal inflammation and prolapse, LPD -/- mice with EHS infection and without rectal inflammation and prolapse; (B) morphometric quantification of average frequency of H2AX positive cells per thousand enterocytes. For each animal, total 8–10 images were obtained and analyzed. Monoclonal rabbit anti-H2AX antibody was used to label cells bearing DNA damage. The secondary antibody was goat anti-Rabbit Ig(H+L), alexa fluor 568 conjugated. Animal number, group LPD -/- control uninfected mice = 6, group LPD -/- EHS-infected with RP = 17, group LPD -/- EHS-infected without RP = 14, group LPD +/- EHS-infected = 10. *** significant at < 0.001. Magnification = 200x; bar = 20μm.</p

Quantitation of EHS in the Lower Bowel of LPD -/- mice.

<p>Levels of EHS colonization were determined by qPCR in the cecum and colon of both RP and CN mice. Organisms were quantified in the rectum only for RP mice, as the normal rectal tissue was less abundant and thus spared for histologic analysis. As expected, EHS were most abundant in the ceca for both groups of mice. Colonization was more variable and tended to decrease distally, yet EHS were still detected in all locations. (RP: Rectal prolapse; CN: Clinically normal).</p

Flow analysis of CD45⁺CD11b⁺Gr1⁺ myeloid cells.

<p>Proportions of myeloid cells increased significantly in LPD^-/- RP mice blood, spleen, and rectal prolapse tissue. Left panel, representative flow plots of CD11b⁺Gr1⁺ myeloid cells from various tissue samples compared RP and control mice, gating on CD45⁺. Right panel, quantification of CD11b⁺Gr1⁺ myeloid cells in CD45⁺ population (n = 3). Error bars, mean ± s.e.m. P values were derived from an unpaired, two-tailed Student’s t-test (* P<0.05; ** P<0.01). CN = Clinically Normal; RP = Rectal Prolapse.</p