A novel mouse model of isolated limb perfusion for extremity melanoma.

BACKGROUND: Isolated limb perfusion (ILP) for extremity melanoma has been used clinically for over half a century. Mouse modeling of ILP may offer significant experimental advantages compared with existing models. We propose a novel mouse model and report our initial experience. METHODS: We injected female C57BL/6 mice (22-25 g) with 1 × 10(6) B16 melanoma cells subcutaneously in the distal right thigh. After 7 d of tumor establishment, we cannulated the superficial femoral artery (inflow) and vein (outflow) of anesthetized mice and placed a proximal tourniquet. Non-oxygenated perfusate included low-dose or high-dose melphalan and saline (control). We analyzed endpoints of cannulation time, procedural complications, morbidity, toxicity, and tumor response. RESULTS: We performed 11 superficial femoral vessel cannulations. Median cannulation time was 19 min (range, 15-32 min). Intact perfusion models were obtained in 10 of 11 cases (91%); one case failed owing to superficial femoral vein dissection. Morbidity rate was 20% (one wound dehiscence and one hematoma). Both high- and low-dose melphalan perfusion groups (4 mice/group) trended to growth delay and regression compared with saline-perfused groups. Toxicity was greater in the high-dose melphalan-treated mice. CONCLUSIONS: We have established the first reproducible mouse model of ILP for melanoma. Future experiments will take advantage of the large number of established mouse knockout models and reagents to dissect the precise mechanisms of tumor control after ILP, and examine to novel agents.

Water: a simple solution for tumor spillage.

BACKGROUND: Although often proposed as a means to reduce the harmful consequences of tumor spill, water lavage has yet to be systematically evaluated in relevant in vitro and in vivo models. This study evaluates the mechanisms and utility of a single water lavage to improve the sequelae of tumor spill during laparotomy. METHODS: Murine colorectal tumor cell susceptibility to water-induced osmotic lysis was characterized in vitro. A reproducible model of tumor spill was established to recapitulate water or saline lavage during laparotomy. Analyses of tumor volumes calculated from noninvasive imaging were performed. The tumor volumes and survival of mice treated with water, normal saline, or sham laparotomy were assessed. RESULTS: Significant osmotic lysis of cultured murine colorectal cancer cells was observed after a brief exposure to water. Compared to saline or sham laparotomy, water lavage demonstrated superior clinical outcomes with a decrease in tumor burden and concomitant improvement in survival. CONCLUSIONS: The use of water lavage during oncologic surgeries to reduce the sequelae of tumor spill is justified and strongly supported by our study. Data from our study raise several concerns regarding the mechanisms and efficacy of saline lavage. Clinically, the use of water lavage during laparotomy would be anticipated to reduce peritoneal disease burden with minimal toxicity or cost.

Expression and functional analysis of human leukocyte antigen class I antigen-processing machinery in medulloblastoma.

Defects in the expression and/or function of the human leukocyte antigen (HLA) class I antigen-processing machinery (APM) components are found in many tumor types. These abnormalities may have a negative impact on the interactions of tumor cells with host's immune system and on the outcome of T cell-based immunotherapy. To the best of our knowledge, no information is available about APM component expression and functional characteristics in human medulloblastoma cells (Mb). Therefore, in the present study, we have initially compared the expression of APM components in Mb, an embryonal pediatric brain tumor with a poor prognosis, with that in noninfiltrating astrocytic pediatric tumors, a group of differentiated brain malignancies with favorable prognosis. LMP2, LMP7, calnexin, beta2-microglobulin-free heavy chain (HC) and beta2-microglobulin were down-regulated or undetectable in Mb lesions, but not in astrocytic tumors or normal fetal cerebellum. Two Mb cell lines (DAOI and D283) displayed similar but not superimposable defects in APM component expression as compared with primary tumors. To assess the functional implications of HLA class I APM component down-regulation in Mb cell lines, we tested their recognition by HLA class I antigen-restricted, tumor antigen (TA)-specific CTL, generated by stimulations with dendritic cells that had been transfected with Mb mRNA. The Mb cell lines were lysed by TA-specific CTL in a HLA-restricted manner. Thus, defective expression of HLA class I-related APM components in Mb cells does not impair their ability to present TA to TA-specific CTL. In conclusion, these results can contribute to optimize T cell-based immunotherapeutic strategies for Mb treatment.

Restriction landmark genomic scanning (RLGS) spot identification by second generation virtual RLGS in multiple genomes with multiple enzyme combinations.

BACKGROUND: Restriction landmark genomic scanning (RLGS) is one of the most successfully applied methods for the identification of aberrant CpG island hypermethylation in cancer, as well as the identification of tissue specific methylation of CpG islands. However, a limitation to the utility of this method has been the ability to assign specific genomic sequences to RLGS spots, a process commonly referred to as "RLGS spot cloning." RESULTS: We report the development of a virtual RLGS method (vRLGS) that allows for RLGS spot identification in any sequenced genome and with any enzyme combination. We report significant improvements in predicting DNA fragment migration patterns by incorporating sequence information into the migration models, and demonstrate a median Euclidian distance between actual and predicted spot migration of 0.18 centimeters for the most complex human RLGS pattern. We report the confirmed identification of 795 human and 530 mouse RLGS spots for the most commonly used enzyme combinations. We also developed a method to filter the virtual spots to reduce the number of extra spots seen on a virtual profile for both the mouse and human genomes. We demonstrate use of this filter to simplify spot cloning and to assist in the identification of spots exhibiting tissue-specific methylation. CONCLUSION: The new vRLGS system reported here is highly robust for the identification of novel RLGS spots. The migration models developed are not specific to the genome being studied or the enzyme combination being used, making this tool broadly applicable. The identification of hundreds of mouse and human RLGS spot loci confirms the strong bias of RLGS studies to focus on CpG islands and provides a valuable resource to rapidly study their methylation.

Multiple defects of the antigen-processing machinery components in human neuroblastoma: immunotherapeutic implications.

Low expression of human leukocyte antigen (HLA) class I in human tumors may be related to defects of the antigen-processing machinery (APM) components. Neuroblastoma cells are virtually HLA class I negative, but (i) the underlying mechanisms are unknown, and (ii) expression of the APM components has never been investigated. Here we have used a panel of novel monoclonal antibodies to proteasomal and immunoproteasomal components, chaperons and transporter associated with antigen processing (TAP) to characterize 24 stroma-poor neuroblastoma tumors and six neuroblastoma cell lines. Primary tumors showed defects in the expression of zeta, tapasin, TAP1 or TAP2, HLA class I heavy chain and beta2 microglobulin, LMP2 and LMP7, as compared to normal adrenal medulla. Neuroblastoma cell lines displayed roughly similar patterns of APM expression in comparison to primary tumors. Incubation of neuroblastoma cell lines with interferon-gamma caused upregulation of HLA class I molecules and reduced lysis by killer inhibitory receptor HLA ligand-matched NK cells. Defects in APM components explain reduced peptide loading on HLA class I molecules, their instability and failure to be expressed on the cell surface. HLA class I upregulation by interferon-gamma, although enhancing neuroblastoma cell recognition by cytotoxic T cells, dampens their susceptibility to NK cells.

Mechanisms of immune evasion of human neuroblastoma.

Neuroblastoma (NB) is a common neuroectodermal tumor of childhood with low response to conventional therapy in patients with advanced stage disease. Among novel strategies, immumotherapy has attracted much interest. However, scanty information is available about the immunogenicity of human NB. Here, we review our data showing that human NB may evade the control mediated by T cytotoxic lymphocytes and natural killer (NK) cells through multiple mechanisms: (i) downregulation of HLA class I molecules and antigen processing machinery components (ii) downregulation of activating ligands for the activating immunoreceptor NKG2D expressed by cytotoxic T lymphocytes and NK cells. Additional mechanisms of immune evasion used by human NB cells are discussed.

Immune Adjuvant Activity of Pre-Resectional Radiofrequency Ablation Protects against Local and Systemic Recurrence in Aggressive Murine Colorectal Cancer.

PURPOSE: While surgical resection is a cornerstone of cancer treatment, local and distant recurrences continue to adversely affect outcome in a significant proportion of patients. Evidence that an alternative debulking strategy involving radiofrequency ablation (RFA) induces antitumor immunity prompted the current investigation of the efficacy of performing RFA prior to surgical resection (pre-resectional RFA) in a preclinical mouse model. EXPERIMENTAL DESIGN: Therapeutic efficacy and systemic immune responses were assessed following pre-resectional RFA treatment of murine CT26 colon adenocarcinoma. RESULTS: Treatment with pre-resectional RFA significantly delayed tumor growth and improved overall survival compared to sham surgery, RFA, or resection alone. Mice in the pre-resectional RFA group that achieved a complete response demonstrated durable antitumor immunity upon tumor re-challenge. Failure to achieve a therapeutic benefit in immunodeficient mice confirmed that tumor control by pre-resectional RFA depends on an intact adaptive immune response rather than changes in physical parameters that make ablated tumors more amenable to a complete surgical excision. RFA causes a marked increase in intratumoral CD8+ T lymphocyte infiltration, thus substantially enhancing the ratio of CD8+ effector T cells: FoxP3+ regulatory T cells. Importantly, pre-resectional RFA significantly increases the number of antigen-specific CD8+ T cells within the tumor microenvironment and tumor-draining lymph node but had no impact on infiltration by myeloid-derived suppressor cells, M1 macrophages or M2 macrophages at tumor sites or in peripheral lymphoid organs (i.e., spleen). Finally, pre-resectional RFA of primary tumors delayed growth of distant tumors through a mechanism that depends on systemic CD8+ T cell-mediated antitumor immunity. CONCLUSION: Improved survival and antitumor systemic immunity elicited by pre-resectional RFA support the translational potential of this neoadjuvant treatment for cancer patients with high-risk of local and systemic recurrence.

Downregulation and/or release of NKG2D ligands as immune evasion strategy of human neuroblastoma.

Neuroblastoma (NB) is a pediatric extracranial tumor characterized by downregulation of human leukocyte antigen class I and defects of the antigen processing machinery, two features that make it an appropriate target for natural killer (NK)-mediated lysis. NKG2D is an activating immunoreceptor expressed by cytotoxic T lymphocytes and NK cells. The ligands for NKG2D are the major histocompatibility complex class I-related chain (MIC)A and MICB glycoproteins, and the UL-16-binding proteins (ULBPs). Here, the expression of NKG2D ligands was investigated in human primary NB tumors and cell lines because scanty information is available on this issue. MICA, MICB, and ULBP transcripts were found in most tumors and cell lines. MICA protein was detected in some NB cell lines but not in primary tumors. A soluble form of MICA (sMICA) was identified in most patient sera and in some cell line supernatants. sMICA downregulated surface NKG2D in normal peripheral blood CD8(+) cells and decreased NK-mediated killing of MICA(+) NB cells. MICB was detected exclusively in the cytosol of primary tumors and cell lines. Approximately 50% of primary tumors expressed ULBP-2, but not ULBP-1 or -3. ULBP-3 was expressed in 5 of 9 cell lines, ULBP-2 in 2 of 9, whereas ULBP-1 was never detected. These studies delineate novel potential pathways of tumor escape and immunodeficiency in NB.

The benefit of intraperitoneal chemotherapy for the treatment of colorectal carcinomatosis.

The clinical practice of hyperthermic intraperitoneal chemoperfusion (HIPEC) for carcinomatosis has lacked preclinical justification. A standardized mouse model was created to evaluate the independent effects of intraperitoneal chemotherapy. Diffuse colorectal carcinomatosis was generated in mice prior to intraperitoneal lavage with mitomycin C (MMC) at clinically comparable dosing for variable lengths of time. Tumor volumes, MMC tissue concentrations and survival were measured in comparison to saline lavage and intravenous MMC. Magnetic resonance imaging revealed a direct correlation between tumor volume, MMC dose and exposure time and survival. Intravenous MMC demonstrated a rapid clearance from the blood, lower peritoneal tissue concentrations, less tumor growth inhibition and decreased survival compared to intraperitoneal administration. Intraperitoneal chemotherapy inhibited tumor growth independent of cytoreduction or hyperthermia, demonstrated improved peritoneal tissue concentration and was associated with increased survival. These data support the clinical utility of the intraperitoneal chemotherapy component of HIPEC.

CTLA-4 is expressed by human monocyte-derived dendritic cells and regulates their functions.

Cytotoxic T lymphocyte antigen-4 (CTLA-4) is the major negative regulator of T-cell responses, although growing evidence supports its wider role as an immune attenuator that may also act in other cell lineages. Here, we have analyzed the expression of CTLA-4 in human monocytes and monocyte-derived dendritic cells (DCs), and the effect of its engagement on cytokine production and T-cell stimulatory activity by mature DCs. CTLA-4 was highly expressed on freshly isolated monocytes, then down-modulated upon differentiation toward immature DCs (iDCs) and it was markedly upregulated on mature DCs obtained with different stimulations (lipopolysaccharides [LPS], Poly:IC, cytokines). In line with the functional role of CTLA-4 in T cells, treatment of mDCs with an agonistic anti-CTLA-4 mAb significantly enhanced secretion of regulatory interleukin (IL)-10 but reduced secretion of IL-8/IL-12 pro-inflammatory cytokines, as well as autologous CD4+ T-cell proliferation in response to stimulation with recall antigen purified protein derivative (PPD) loaded-DCs. Neutralization of IL-10 with an anti-IL-10 antibody during the mDCs-CD4+ T-cell co-culture partially restored the ability of anti-CTLA-4-treated mDCs to stimulate T-cell proliferation in response to PPD. Taken together, our data provide the first evidence that CTLA-4 receptor is expressed by human monocyte-derived mDCs upon their full activation and that it exerts immune modulatory effects.

Phenotype-specific CpG island methylation events in a murine model of prostate cancer.

Aberrant DNA methylation plays a significant role in nearly all human cancers and may contribute to disease progression to advanced phenotypes. Study of advanced prostate cancer phenotypes in the human disease is hampered by limited availability of tissues. We therefore took advantage of the Transgenic Adenocarcinoma of Mouse Prostate (TRAMP) model to study whether three different phenotypes of TRAMP tumors (PRIM, late-stage primary tumors; AIP, androgen-independent primary tumors; and MET, metastases) displayed specific patterns of CpG island hypermethylation using Restriction Landmark Genomic Scanning. Each tumor phenotype displayed numerous hypermethylation events, with the most homogeneous methylation pattern in AIP and the most heterogeneous pattern in MET. Several loci displayed a phenotype-specific methylation pattern; the most striking pattern being loci methylated at high frequency in PRIM and AIP but rarely in MET. Examination of the mRNA expression of three genes, BC058385, Goosecoid, and Neurexin 2, which exhibited nonpromoter methylation, revealed increased expression associated with downstream methylation. Only methylated samples showed mRNA expression, in which tumor phenotype was a key factor determining the level of expression. The CpG island in the human orthologue of BC058385 was methylated in human AIP but not in primary androgen-stimulated prostate cancer or benign prostate. The clinical data show a proof-of-principle that the TRAMP model can be used to identify targets of aberrant CpG island methylation relevant to human disease. In conclusion, phenotype-specific hypermethylation events were associated with the overexpression of different genes and may provide new markers of prostate tumorigenesis.