Jennifer M. McNiff

A common human skin tumour is caused by activating mutations in β-catenin

WNT signalling orchestrates a number of developmental programs. In response to this stimulus, cytoplasmic β-catenin (encoded by CTNNB1 ) is stabilized, enabling downstream transcriptional activation by members of the LEF/TCF family. One of the target genes for β-catenin/TCF encodes c-MYC, explaining why constitutive activation of the WNT pathway can lead to cancer, particularly in the colon. Most colon cancers arise from mutations in the gene encoding adenomatous polyposis coli (APC), a protein required for ubiquitin-mediated degradation of β-catenin, but a small percentage of colon and some other cancers harbour β-catenin–stabilizing mutations (refs 8,9,10,11, 12,13,14,15,16, 17). Recently, we discovered that transgenic mice expressing an activated β-catenin are predisposed to developing skin tumours resembling pilomatricomas. Given that the skin of these adult mice also exhibits signs of de novo hair-follicle morphogenesis, we wondered whether human pilomatricomas might originate from hair matrix cells and whether they might possess β-catenin–stabilizing mutations. Here, we explore the cell origin and aetiology of this common human skin tumour. We found nuclear LEF-1 in the dividing tumour cells, providing biochemical evidence that pilomatricomas are derived from hair matrix cells. At least 75% of these tumours possess mutations affecting the amino-terminal segment, normally involved in phosphorylation-dependent, ubiquitin-mediated degradation of the protein. This percentage of CTNNB1 mutations is greater than in all other human tumours examined thus far, and directly implicates β-catenin/LEF misregulation as the major cause of hair matrix cell tumorigenesis in humans.

Memory CD4+ T cells do not induce graft-versus-host disease

Graft-versus-host disease (GVHD) remains a major cause of morbidity and mortality in allogeneic stem cell transplantation (alloSCT). Donor T cells that accompany stem cell grafts cause GVHD by attacking recipient tissues; therefore, all patients receive GVHD prophylaxis by depletion of T cells from the allograft or through immunosuppressant drugs. In addition to providing a graft-versus-leukemia effect, donor T cells are critical for reconstituting T cell-mediated immunity. Ideally, immunity to infectious agents would be transferred from donor to host without GVHD. Most donors have been exposed to common pathogens and have an increased precursor frequency of memory T cells against pathogenic antigens. We therefore asked whether memory CD62L-CD44+ CD4+ T cells would induce less GVHD than unfractionated or naive CD4+ T cells. Strikingly, we found that memory CD4 cells induced neither clinical nor histologic GVHD. This effect was not due to the increased number of CD4+CD25+ regulatory T cells found in the CD62L-CD44+ fraction because memory T cells depletion of these cells did not cause GVHD. Memory CD4 cells engrafted and responded to antigen both in vivo and in vitro. If these murine results are applicable to human alloSCT, selective administration of memory T cells could greatly improve post-transplant immune reconstitution.

Donor APCs are required for maximal GVHD but not for GVL.

Graft-versus-host disease (GVHD) is a major source of morbidity in allogenic stem cell transplantation. We previously showed that recipient antigen-presenting cells (APCs) are required for CD8-dependent GVHD in a mouse model across only minor histocompatibility antigens (minor H antigens). However, these studies did not address the function of donor-derived APCs after GVHD is initiated. Here we show that GVHD develops in recipients of donor major histocompatibility complex class I–deficient (MHC I−) bone marrow. Thus, after initial priming, CD8 cells caused GVHD without a further requirement for hematopoietic APCs, indicating that host APCs are necessary and sufficient for GHVD. Nonetheless, GVHD was less severe in recipients of MHC I− bone marrow. Therefore, once initiated, GVHD is intensified by donor-derived cells, most probably donor APCs cross-priming alloreactive CD8 cells. Nevertheless, donor APCs were not required for CD8-mediated graft-versus-leukemia (GVL) against a mouse model of chronic-phase chronic myelogenous leukemia. These studies identify donor APCs as a new target for treating GVHD, which may preserve GVL.

IL-10 Regulates Murine Lupus

MRL/MpJ-Tnfrsf6lpr (MRL/MpJ-Faslpr; MRL-Faslpr) mice develop a spontaneous lupus syndrome closely resembling human systemic lupus erythematosus. To define the role of IL-10 in the regulation of murine lupus, IL-10 gene-deficient (IL-10−/−) MRL-Faslpr (MRL-Faslpr IL-10−/−) mice were generated and their disease phenotype was compared with littermates with one or two copies of an intact IL-10 locus (MRL-Faslpr IL-10+/− and MRL-Faslpr IL-10+/+ mice, respectively). MRL-Faslpr IL-10−/− mice developed severe lupus, with earlier appearance of skin lesions, increased lymphadenopathy, more severe glomerulonephritis, and higher mortality than their IL-10-intact littermate controls. The increased severity of lupus in MRL-Faslpr IL-10−/− mice was closely associated with enhanced IFN-γ production by both CD4+ and CD8+ cells and increased serum concentration of IgG2a anti-dsDNA autoantibodies. The protective effect of IL-10 in this lupus model was further supported by the observation that administration of rIL-10 reduced IgG2a anti-dsDNA autoantibody production in wild-type MRL-Faslpr animals. In summary, our results provide evidence that IL-10 can down-modulate murine lupus through inhibition of pathogenic Th1 cytokine responses. Modulation of the level of IL-10 may be of potential therapeutic benefit for human lupus.

Target Antigens Determine Graft-versus-Host Disease Phenotype

Chronic graft-vs-host disease (cGVHD) is an increasingly frequent complication of allogeneic stem cell transplantation. Phenotypically, cGVHD differs from patient to patient; in particular, a subset of patients develops extensive cutaneous fibrosis. Similarly, graft-vs-host disease (GVHD) is distinct in inbred murine donor:recipient pairings, indicating a genetic component to disease phenotype. The B10.D2 → BALB/c (H-2d) strain pairing uniquely recapitulates key pathologic features of fibrotic human cutaneous cGVHD. To distinguish whether this genetic component is due to differences in genes that modulate immune responses or to the specific Ags targeted, we asked whether skin-dominant cGVHD also develops in the B10 → BALB.B (H-2b) and B10.BR → BALB.K (H-2k) MHC-congenic pairings. Because each MHC haplotype presents different peptides and selects different T cell repertoires, GVHD in each donor:recipient pair undoubtedly targets different Ags. We found that, in contrast to BALB/c recipients, BALB.B mice never manifested skin disease while BALB.K mice developed a modified form of skin disease. Instead, BALB.B and BALB.K recipients developed systemic GVHD which was absent in BALB/c mice. Moreover, in (B10 × B10.D2)F1 → (BALB.B × BALB/c)F1 H-2b/d transplants, recipients developed both cutaneous and systemic disease. Thus, the selection of immunodominant Ags determines the target and character of GVHD, providing insight into the genetic basis for different forms of GVHD.

TRAIL Induces Apoptosis and Inflammatory Gene Expression in Human Endothelial Cells

Human TRAIL can efficiently kill tumor cells in vitro and kill human tumor xenografts in mice with little effect on normal mouse cells or tissues. The effects of TRAIL on normal human tissues have not been described. In this study, we report that endothelial cells (EC), isolated from human umbilical veins or human dermal microvessels, express death domain-containing TRAIL-R1 and -R2. Incubation with TRAIL for 15 h causes ∼30% of cultured EC to die, as assessed by propidium iodide uptake. Death is apoptotic, as assessed by Annexin V staining, 4′,6′-diamidino-2-phenylindole staining, and DNA fragment ELISA. EC death is increased by cotreatment with cycloheximide but significantly reduced by caspase inhibitors or transduced dominant-negative Fas-associated death domain protein. In surviving cells, TRAIL activates NF-κB, induces expression of E-selectin, ICAM-1, and IL-8, and promotes adhesion of leukocytes. Injection of TRAIL into human skin xenografts promotes focal EC injury accompanied by limited neutrophil infiltration. These data suggest that TRAIL is an inducer of tissue injury in humans, an outcome that may influence antitumor therapy with TRAIL.

Melanoma × macrophage hybrids with enhanced metastatic potential

Studies were conducted on the hypothesis that melanoma metastasis might be initiated through the gener-ation of hybrids comprised of cells of the primary tumor and tumor-infiltrating leukocytes. Fusion hybrids were generated in vitro between weakly metastatic Cloudman S91 mouse melanoma cells and normal mouse or human macrophages. Hybrids were implanted s.c. in the tail and mice were monitored for metastases. Controls included parental S91 cells, autologous S91 × S91 hybrids, and B16F10 melanoma cells. Of 35 hybrids tested, most were more aggressive than the parental melanoma cells, producing metastases sooner and in more mice. A striking characteristic was heterogeneity amongst hybrids, with some lines producing no metastases and others producing metastases in up to 80% of mice. With few exceptions, hybrids with the highest metastatic potential also had the highest basal melanin content whereas those with the lowest metastatic potential were basally amelanotic, as were t he parental melanoma cells. A spontaneous in vivo supermelanotic hybrid between an S91 tumor cell and DBA/2J host cell was one of the most metastatic lines. Hybrids with the highest metastatic potential also exhibited markedly higher chemotaxis to fibroblast-conditioned media. Histologically, the metastatic hybrids demonstrated vascular invasion and spread to distant organs similar to that of metastatic melanomas in mice and humans. Thus previous findings of enhanced metastasis in leukocyte × lymphoma hybrids can now be extended to include leukocyte × melanoma hybrids. Whether such hybridization is a natural cause of metastasis in vivo remains to be determined; however the fusion hybrids with genetically-matched parents described herein so closely resembled naturally- occurring metastatic melanoma cells that they could serve as useful new models for studies of this complex and deadly phenomenon.

Memory T Cells and Their Costimulators in Human Allograft Injury

Both CD4+ and CD8+ human memory but not naive T cells respond to allogeneic human dermal microvascular endothelial cells (HDMEC) in vitro by secreting cytokines and by proliferating. Several recently identified costimulators, namely, 4-1BB ligand, ICOS ligand, and OX40 ligand, are up-regulated on cultured HDMEC in response to TNF or coculture with allogeneic T cells. Blockade of these costimulators each partially reduces IFN-γ and IL-2 secretion and proliferation of previously resting memory T cells. The effects of these costimulators are overlapping but not identical. Memory but not naive T cells are the principal effectors of microvascular injury in human skin allografts following adoptive transfer into immunodeficient mice. Furthermore, blocking 4-1BB ligand, ICOS ligand, or OX40 ligand in this model reduces human skin allograft injury and T cell effector molecule expression. These data demonstrate that human memory T cells respond to microvascular endothelial cells and can injure allografts in vivo without priming. Furthermore, several recently described costimulators contribute to these processes.

Novel inactivating mutations of transforming growth factor-β type I receptor gene in head-and-neck cancer metastases

Carcinoma cell lines are frequently refractory to transforming growth factor‐β (TGFβ)‐mediated cell cycle arrest. Whether and how TGFβ signaling is disrupted in the majority of human tumors, however, remains unclear. To investigate whether TGFβ signaling might be disrupted by inactivation of the key signaling molecule, the TGFβ type I (TβR‐I) receptor, and whether or not TβR‐I inactivation is associated with late stage disease, we conducted a comprehensive structural analysis of the TβR‐I gene in fine‐needle aspirates of 23 head‐&‐neck cancer metastases. We encountered 4 different mutations of TβR‐I, 3 of which have not been previously identified. In 1 case, we found a somatic intragenic 4‐bp deletion predicting for a truncation of the receptor protein. This is the first example of a true loss‐of‐function mutation of TβR‐I in a human epithelial neoplasm. In 2 other cases, we identified missense mutations located between the juxtamembrane‐ and serine‐threonine kinase domains. One of these resulted in an alanine‐to‐threonine substitution (A230T), which disrupts receptor signaling activity by causing rapid protein degradation within the endoplasmatic reticulum. This represents a novel mechanism of inactivation of a TGFβ signaling intermediate. Finally, we identified a serine‐to‐tyrosine substitution at codon 387 (S387Y) in a metastasis but not in the corresponding primary tumor. We had previously shown this S387Y mutant to be predominantly associated with breast cancer metastases and to have a diminished ability to mediate TGFβ‐dependent signaling. In aggregate, these findings provide further support for the hypothesis that inactivation of the TGFβ signaling pathway occurs in a significant subset of human cancers.

Primary Cutaneous B-Cell Lymphoma Treated With Radiotherapy: A Comparison of the European Organization for Research and Treatment of Cancer and the WHO Classification Systems

PURPOSE To determine the relationship between the WHO and European Organization for Research and Treatment of Cancer (EORTC) pathologic classifications for primary cutaneous B-cell lymphoma (CBCL) and the implication of this relationship on initial treatment. PATIENTS AND METHODS Patients with primary CBCL treated with radiotherapy were identified retrospectively. Initial biopsy specimens were reviewed by two dermatopathologists and classified according to the EORTC and WHO systems. Primary outcomes were recurrence-free and overall survival. RESULTS Thirty-four patients were identified; initial biopsy specimens were adequate for classification in 32 patients. Four different composite histopathologic subtypes of lymphoma were identified: 53% (17 of 32) follicle center cell by EORTC and diffuse large B-cell by WHO (FCC/DLB), 25% (eight of 32) follicle center cell by EORTC and follicular by WHO (FCC/Fol), 13% (four of 32) marginal zone by EORTC and WHO (MZ/MZ), and 9% (three of 32) large B-cell of the leg by EORTC and diffuse large B-cell by WHO (Leg/DLB). Five-year relapse-free survival ranged from 62% to 73% for FCC/DLB, FCC/Fol, and MZ/MZ but was 33% for Leg/DLB (P =.6). Five-year overall survival was 100% for FCC/DLB, FCC/Fol, and MZ/MZ but was 67% for Leg/DLB (P =.07). At 5 years, 21% of all patients had developed extracutaneous disease. CONCLUSION Two-thirds of primary cutaneous FCC lymphomas by EORTC criteria satisfy WHO criteria for DLB lymphoma. Unlike DLB lymphoma presenting in nodal or noncutaneous sites, these lesions are associated with an indolent course and may be treated with local radiotherapy alone.