Association with clinical outcome of expression of VLA-4 in primary cutaneous malignant melanoma as well as P-selectin and E-selectin on intratumoral vessels

PET Imaging of VLA-4 in a New BRAFV600E Mouse Model of Melanoma

PURPOSE

Despite unprecedented responses to immune checkpoint inhibitors and targeted therapy in melanoma, a major subset of patients progresses and have few effective salvage options. We have previously demonstrated robust, selective uptake of the peptidomimetic LLP2A labeled with Cu-64 ([64Cu]-LLP2A) for positron emission tomography (PET) imaging in subcutaneous and metastatic models of B16F10 murine melanoma. LLP2A binds with high affinity to very late antigen-4 (VLA-4, integrin α4β1), a transmembrane protein overexpressed in melanoma and other cancers that facilitates tumor growth and metastasis. Yet B16F10 fails to faithfully reflect human melanoma biology, as it lacks certain oncogenic driver mutations, including BRAF mutations found in ≥ 50 % of clinical specimens. Here, we evaluated the PET tracer [64Cu]-CB-TE1A1P-PEG4-LLP2A ([64Cu]-LLP2A) in novel, translational BRAFV600E mutant melanoma models differing in VLA-4 expression-BPR (VLA-4-) and BPRα (VLA-4+).

PROCEDURES

BPR cells were transduced with α4 (CD49d) to overexpress intact cell surface VLA-4 (BPRα). The binding affinity of [64Cu]-LLP2A to BPR and BPRα cells was determined by saturation binding assays. [64Cu]-LLP2A internalization into B16F10, BPR, and BPRα cells was quantified via a plate-based assay. Tracer biodistribution and PET/CT imaging were evaluated in mice bearing subcutaneous BPR and BPRα tumors.

RESULTS

[64Cu]-LLP2A demonstrated high binding affinity to BPRα (Kd = 1.4 nM) but indeterminate binding to BPR cells. VLA-4+ BPRα and B16F10 displayed comparable time-dependent [64Cu]-LLP2A internalization, whereas BPR internalization was undetectable. PET/CT showed increased tracer uptake in BPRα tumors vs. BPR tumors in vivo, which was validated by significantly greater (p < 0.0001) BPRα tumor uptake in biodistribution analyses.

CONCLUSIONS

[64Cu]-LLP2A discriminates BPRα (VLA-4+) vs. BPR (VLA-4-) melanomas in vivo, supporting translation of these BRAF-mutated melanoma models via prospective imaging and theranostic studies. These results extend the utility of LLP2A to selectively target clinically relevant and therapy-resistant tumor variants toward its use for therapeutic patient care.

Melanoma‐derived extracellular vesicles mediate lymphatic remodelling and impair tumour immunity in draining lymph nodes

Tumour‐draining lymph nodes (LNs) undergo massive remodelling including expansion of the lymphatic sinuses, a process that has been linked to lymphatic metastasis by creation of a pre‐metastatic niche. However, the signals leading to these changes have not been completely understood. Here, we found that extracellular vesicles (EVs) derived from melanoma cells are rapidly transported by lymphatic vessels to draining LNs, where they selectively interact with lymphatic endothelial cells (LECs) as well as medullary sinus macrophages. Interestingly, uptake of melanoma EVs by LN‐resident LECs was partly dependent on lymphatic VCAM‐1 expression, and induced transcriptional changes as well as proliferation of those cells. Furthermore, melanoma EVs shuttled tumour antigens to LN LECs for cross‐presentation on MHC‐I, resulting in apoptosis induction in antigen‐specific CD8⁺ T cells. In conclusion, our data identify EV‐mediated melanoma—LN LEC communication as a new pathway involved in tumour progression and tumour immune inhibition, suggesting that EV uptake or effector mechanisms in LECs might represent a new target for melanoma therapy.

Transcriptomic and genomic heterogeneity in blastic plasmacytoid dendritic cell neoplasms: from ontogeny to oncogenesis

Oncogenesis and ontogeny of blastic plasmacytoid dendritic cell neoplasm (BPDCN) remain uncertain, between canonical plasmacytoid dendritic cells (pDCs) and AXL+ SIGLEC6+ DCs (AS-DCs). We compared 12 BPDCN to 164 acute leukemia by Affymetrix HG-U133 Plus 2.0 arrays: BPDCN were closer to B-cell acute lymphoblastic leukemia (ALL), with enrichment in pDC, B-cell signatures, vesicular transport, deubiquitination pathways, and AS-DC signatures, but only in some cases. Importantly, 1 T-cell ALL clustered with BPDCN, with compatible morphology, immunophenotype (cCD3+ sCD3- CD123+ cTCL1+ CD304+), and genetics. Many oncogenetic pathways are deregulated in BPDCN compared with normal pDC, such as cell-cycle kinases, and importantly, the transcription factor SOX4, involved in B ontogeny, pDC ontogeny, and cancer cell invasion. High-throughput sequencing (HaloPlex) showed myeloid mutations (TET2, 62%; ASXL1, 46%; ZRSR2, 31%) associated with lymphoid mutations (IKZF1), whereas single-nucleotide polymorphism (SNP) array (Affymetrix SNP array 6.0) revealed frequent losses (mean: 9 per patient) involving key hematological oncogenes (RB1, IKZF1/2/3, ETV6, NR3C1, CDKN2A/B, TP53) and immune response genes (IFNGR, TGFB, CLEC4C, IFNA cluster). Various markers suggest an AS-DC origin, but not in all patients, and some of these abnormalities are related to the leukemogenesis process, such as the 9p deletion, leading to decreased expression of genes encoding type I interferons. In addition, the AS-DC profile is only found in a subgroup of patients. Overall, the cellular ontogenic origin of BPDCN remains to be characterized, and these results highlight the heterogeneity of BPDCN, with a risk of a diagnostic trap.

Advances in Receptor-Targeted Radiolabeled Peptides for Melanoma Imaging and Therapy

Melanocortin-1 receptor (MC1R) and very late antigen-4 (VLA-4, integrin α₄β₁) are 2 attractive molecular targets for developing peptide radiopharmaceuticals for melanoma imaging and therapy. MC1R- and VLA-4-targeting peptides and peptide-conjugated Cornell prime dots (C' dots) can serve as delivery vehicles to target both diagnostic and therapeutic radionuclides to melanoma cells for imaging and therapy. This review highlights the advances of MC1R- and VLA-4-targeted radiolabeled peptides and peptide-conjugated C' dots for melanoma imaging and therapy. The promising preclinical and clinical results of these new peptide radiopharmaceuticals present an optimistic outlook for clinical translation into receptor-targeting melanoma imaging and radionuclide therapy in the future.

Targeting the cutaneous lymphocyte antigen (CLA) in inflammatory and neoplastic skin conditions

Introduction: The cutaneous lymphocyte antigen interacts with E-selectin on endothelial cells and is expressed on 15% of circulating T-cells. Skin-homing T-cells express the cutaneous lymphocyte antigen and play a role in local cutaneous immunity in inflammatory reactions and neoplastic conditions.Areas covered: Lymphocyte extravasation is the essential para-physiological mechanism enabling immune surveillance of tissues for tumors as well as effector cell recruitment to inflammatory sites.The authors focused on skin inflammatory disorders, on cutaneous lymphoproliferative disease, and on other skin malignancies.Expert opinion: Interfering with leukocyte extravasation has been regarded as an attractive strategy in skin disorders, in the past for inflammatory conditions and more recently for cutaneous T-cell lymphomas. Therapeutic blocking of skin-homing interactions has been attempted in psoriasis and atopic dermatitis and has been achieved in the treatment of cutaneous T-cell lymphomas. Cutaneous lymphocyte antigen is a potential molecular target for both systemic and skin-directed therapy for cutaneous T-cell lymphomas.

VLA-4 mediated adhesion of melanoma cells on the blood-brain barrier is the critical cue for melanoma cell intercalation and barrier disruption

Melanoma is the most aggressive skin cancer in humans. One severe complication is the formation of brain metastasis, which requires extravasation of melanoma cells across the tight blood-brain barrier (BBB). Previously, VLA-4 has been assigned a role for the adhesive interaction of melanoma cells with non-BBB endothelial cells. However, the role of melanoma VLA-4 for breaching the BBB remained unknown. In this study, we used a mouse in vitro BBB model and imaged the shear resistant arrest of melanoma cells on the BBB. Similar to effector T cells, inflammatory conditions of the BBB increased the arrest of melanoma cells followed by a unique post-arrest behavior lacking immediate crawling. However, over time, melanoma cells intercalated into the BBB and compromised its barrier properties. Most importantly, antibody ablation of VLA-4 abrogated melanoma shear resistant arrest on and intercalation into the BBB and protected the BBB from barrier breakdown. A tissue microarray established from human brain metastasis revealed that indeed a majority of 92% of all human melanoma brain metastases stained VLA-4 positive. We propose VLA-4 as a target for the inhibition of brain metastasis formation in the context of personalized medicine identifying metastasizing VLA-4 positive melanoma.

The First Step in Adoptive Cell Immunotherapeutics: Assuring Cell Delivery via Glycoengineering

Despite decades of intensive attention directed to creation of genetically altered cells (e.g., as in development of chimeric antigen receptor (CAR) T-cells) and/or to achieve requisite in vitro accumulation of desired immunologic effectors (e.g., elaboration of virus-specific T cells, expansion of NK cells, differentiation of dendritic cells, isolation, and propagation of Tregs, etc.), there has been essentially no interest in the most fundamental of all hurdles: assuring tissue-specific delivery of administered therapeutic cells to sites where they are needed. With regards to use of CAR T-cells, the absence of information on the efficacy of cell delivery is striking, especially in light of the clear association between administered cell dose and adverse events, and the obvious fact that pertinent cell acquisition/expansion costs would be dramatically curtailed with more efficient delivery of the administered cell bolus. Herein, based on information garnered from studies of human leukocytes and adult stem cells, the logic underlying the use of cell surface glycoengineering to enforce E-selectin ligand expression will be conveyed in the context of how this approach offers strategies to enhance delivery of CAR T-cells to marrow and to tumor beds. This application of glycoscience principles and techniques with intention to optimize cell therapeutics is a prime example of the emerging field of “translational glycobiology.”

Combined VLA-4-Targeted Radionuclide Therapy and Immunotherapy in a Mouse Model of Melanoma

Very late antigen-4 (VLA-4; also known as integrin α₄β₁) is expressed at high levels in aggressive and metastatic melanoma tumors and may provide an ideal target for imaging and targeted radionuclide therapy (TRT). ¹⁷⁷Lu-DOTA-PEG₄-LLP2A (¹⁷⁷Lu-LLP2A) is a TRT that shows high affinity for VLA-4 and high uptake in B16F10 mouse melanoma tumors in vivo. Here, we report efficacy studies of ¹⁷⁷Lu-LLP2A, alone and combined with immune checkpoint inhibitors (ICIs) (anti-PD-1, anti-PD-L1, and anti-CTLA-4 antibodies), in B16F10 tumor-bearing mice. Methods: Tumor cells (1 × 10⁶) were implanted subcutaneously in C57BL/6 mice. After 8-10 d, the mice were randomized into 8 groups. ¹⁷⁷Lu-LLP2A was injected intravenously on day 8 or 9 (single dose), and ICI antibodies were administered intraperitoneally in 3 doses. Tumor growth was monitored over time via calipers. Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining for apoptosis was performed on fixed tumors. In a separate study, Cy3-LLP2A or Cy3-scrambled LLP2A was injected in tumor-bearing mice, and tumors were collected 4 h after injection and then analyzed by flow cytometry and immunofluorescence microscopy using different immune cell markers. Results: TRT alone showed efficacy comparable to the dual-ICI anti-PD-1 + anti-CTLA-4 or anti-PD-L1 + anti-CTLA-4, whereas TRT + ICIs significantly enhanced survival. TUNEL staining showed that the highest levels of apoptosis were in the TRT + ICI groups. In addition to targeting tumor cells, TRT also bound immune cells in the tumor microenvironment. Flow cytometry data showed that the tumors consisted of about 77% tumor cells and fibroblasts (CD45-negative/CD49d-positive) and about 23% immune cells (CD45-positive/CD49d-positive) and that immune cells expressed higher levels of VLA-4. Cy3-LLP2A and CD49d colocalized with macrophages (CD68), T cells (CD8, CD4), and B cells (CD19). Immunohistochemical analysis identified a significant colocalization of Cy3-LLP2A and CD68. Conclusion: Combination treatment with TRT + ICIs targets both tumor cells and immune cells and has potential as a therapeutic agent in patients with metastatic melanoma.

Preliminary evaluation of 18F-labeled LLP2A-trifluoroborate conjugates as VLA-4 (α4β1 integrin) specific radiotracers for PET imaging of melanoma

INTRODUCTION

The transmembrane α₄β₁ integrin receptor, or very-late antigen 4 (VLA-4), is associated with tumor metastasis and angiogenesis, the development of chemotherapeutic drug resistance, and is overexpressed in multiple myelomas, osteosarcomas, lymphomas, leukemias, and melanomas. The peptidomimetic, LLP2A, is a high-affinity ligand with specificity for the extracellular portion of VLA-4 and several conjugates have been evaluated in vivo by NIR-fluorescence, ¹¹¹In-SPECT and ⁶⁸Ga- and ⁶⁴Cu-PET imaging, but to date, not with ¹⁸F-PET.

METHODS

Using two highly stable organotrifluoroborate prosthetic groups: ammoniumdimethyl-trifluoroborate (AMBF₃) and a new N-pyridinyl-para-trifluoroborate (N-Pyr-p-BF₃), both capable of facile aqueous ¹⁸F-labeling by isotope exchange (IEX), we present the first PET imaging evaluations of two [¹⁸F]R-BF₃^--PEG₂-LLP2A tracers using VLA-4 overexpressing B16-F10 murine melanoma tumor mouse models.

RESULTS

Here, we demonstrate successful one-step ¹⁸F-labeling of both conjugates with wet NCA [¹⁸F]F^- in radiochemical yields of up to 11.6% within 75 min at molar activities of 40-100 GBq/μmol. Average tumor uptake values based on ex vivo biodistribution values were 4.4%ID/g (11) and 2.8%ID/g (12) using ¹⁸F-labeled LLP2A-conjugates with the two prosthetic groups: N-Pyr-p-BF₃ (5) and alkyl-N,N-dimethylammonio-BF₃ (AMBF₃) (7), respectively, and was found to be target-specific as evidenced by in vivo blocking controls. Dynamic PET scanning and biodistribution studies revealed slow clearance of the [¹⁸F]R-BF₃^--PEG₂-LLP2A tracers from the tumors, and also substantial uptake in the intestines, gall bladder, liver and bladder. Observed bone uptake was blockable, consistent with known VLA-4 expression in hematopoietic stem cells found in bone marrow.

CONCLUSIONS

These studies show that these [¹⁸F]R-BF₃^--PEG₂-LLP2A conjugates (11 and 12) are promising VLA-4 targeting radiotracers, yet, further optimization will be required to reduce uptake in the gastro-intestinal tract.

Facile synthesis and 18F-radiolabeling of α4β1-specific LLP2A-aryltrifluoroborate peptidomimetic conjugates

The peptidomimetic, LLP2A, is a specific, high-affinity ligand for α₄β₁ integrin receptors. Previously, several PEGylated LLP2A conjugates were evaluated in vivo as imaging agents for the detection of lymphoma, leukemia, multiple myeloma and melanoma tumours via NIR-fluorescence, ¹¹¹In-SPECT, and ⁶⁴Cu- and ⁶⁸Ga-PET imaging. Despite these successes, to date there is no report of an ¹⁸F-labeled LLP2A conjugate. Notably, fluorine-18 is a preferred radionuclide for PET imaging, yet its short half-life and general inactivity under aqueous conditions present challenges for peptide labeling. A simple method for labeling complex biomolecules can be achieved with arylboronic acids that readily capture aqueous [¹⁸F]-fluoride ion resulting in an ¹⁸F-labeled aryltrifluoroborate ([¹⁸F]-ArBF₃^-) radioprosthetic group. Herein, we present the first radiosynthesis of an ¹⁸F-labeled LLP2A conjugate by both one-step ¹⁸F-labeling and one-pot two-step ¹⁸F-labeling post-'click' conjugation of the ¹⁸F-alkynyl-ArBF₃^- prosthetic. Competition with a fluorescent conjugate of LLP2A demonstrated specific binding of the non-radioactive isotopolog ArBF₃^--PEG₂-LLP2A to α₄β₁ integrin-expressing MOLT-4 leukemia cells, as evidenced and confirmed by fluorescence microscopy. This work provides a key first step in the development of an expanding library of [¹⁸F]-R-BF₃^--LLP2A radiotracers for PET imaging.

Melanoma-derived IL-1 converts vascular endothelium to a proinflammatory and procoagulatory phenotype via NFκB activation

Spreading of melanoma is associated with efficient extravasation of circulating tumor cells from the vascular system into distant target organs. This process is accompanied and supported by proinflammatory and procoagulatory conditions. In this study, we analysed the ability of human melanoma cell lines to activate endothelial cells (ECs) in vitro. Some melanoma cells, that is, MV3, were shown to trigger an prompt calcium-flux-dependent, procoagulatory endothelial response that was accompanied by luminal release of ultra-large von Willebrand factor (ULVWF) fibres that were immobilized to the endothelial surface layer. In contrast to MV3-derived supernatant, prolonged treatment of ECs with WM9-derived supernatant mediated a pronounced activation of nuclear factor kappa B (NFκB). NFκB activation in ECs was dependent on both IL-1α and IL-1β secreted from melanoma cells. Melanoma-derived IL-1 mediated an upregulation of proinflammatory cytokines IL-6 and IL-8, the intercellular adhesion molecule-1 (ICAM-1), the vascular cell adhesion molecule-1 (VCAM-1) and the procoagulatory tissue factor (TF) in ECs. Our data show that melanoma cells activate ECs either directly and within seconds or by an IL-1-mediated NFκB activation. Both pathways of EC activation convert the regular repressive function of ECs on inflammation and coagulation to a proinflammatory and procoagulatory surface that supports tumor progression.

Assessing Tumor Angiogenesis in Histological Samples

Tumor neovascularization acquires their vessels through a number of processes including angiogenesis, vasculogenesis, vascular remodeling, intussusception, and possibly vascular mimicry in certain tumors. The end result of the tumor vasculature has been quantified by counting the number of immunohistochemically identified microvessels in areas of maximal vascularity, so-called hot spot. Other techniques have been developed such as Chalkley counting and the use of image analysis systems that are robust and reproducible as well as being more objective. Many of the molecular pathways that govern tumor neovascularization have been identified and many reagents are now available to study these tissue sections. These include angiogenic growth factors and their receptors and cell adhesion molecules, proteases, and markers of activated, proliferating, cytokine-stimulated, or angiogenic vessels, such as CD105. It is also possible to differentiate quiescent from active vessels. Other reagents that can identify proteins involved in microenvironmental influences such as hypoxia have also been generated. Although the histological assessment of tumor vascularity is used mostly in the research context, it may also have clinical applications if appropriate methodology and trained observers perform the studies.

Peptide vaccination in Montanide adjuvant induces and GM-CSF increases CXCR3 and cutaneous lymphocyte antigen expression by tumor antigen-specific CD8 T cells

T cell infiltration of melanoma is associated with enhanced clinical efficacy and is a desirable endpoint of immunotherapeutic vaccination. Infiltration is regulated, in part, by chemokine receptors and selectin ligands on the surface of tumor-specific lymphocytes. Therefore, we investigated the expression of two homing molecules--CXCR3 and CLA - on vaccine-induced CD8 T cells, in the context of a clinical trial of a melanoma-specific peptide vaccine. Both CXCR3 and CLA have been associated with T cell infiltration of melanoma. We demonstrate that a single subcutaneous/intradermal administration of peptide vaccine in Montanide adjuvant induces tumor-specific CD8 T cells that are predominantly positive for CXCR3, with a subpopulation of CXCR3(+)CLA(+) cells. Addition of GM-CSF significantly enhances CXCR3 expression and increases the proportion of CLA-expressing cells. Concurrent with CXCR3 and CLA expression, vaccine-induced CD8 cells express high levels of Tbet, IFN-γ, and IL-12Rβ1. Collectively, these studies demonstrate that peptide vaccination in adjuvant induces CD8 T cells with a phenotype that may support infiltration of melanoma.

PET imaging of very late antigen-4 in melanoma: comparison of 68Ga- and 64Cu-labeled NODAGA and CB-TE1A1P-LLP2A conjugates

Melanoma is a malignant tumor derived from epidermal melanocytes, and it is known for its aggressiveness, therapeutic resistance, and predisposition for late metastasis. Very late antigen-4 (VLA-4; also called integrin α4β1) is a transmembrane noncovalent heterodimer overexpressed in melanoma tumors that plays an important role in tumor growth, angiogenesis, and metastasis by promoting adhesion and migration of cancer cells. In this study, we evaluated 2 conjugates of a high-affinity VLA-4 peptidomimetic ligand, LLP2A, for PET/CT imaging in a subcutaneous and metastatic melanoma tumor.

METHODS

LLP2A was conjugated to 1,4,8,11-tetraazacyclotetradecane-1-(methane phosphonic acid)-8-(methane carboxylic acid) (CB-TE1A1P) and 2-(4,7-bis(carboxymethyl)-1,4,7-triazonan-1-yl)pentanedioic acid (NODAGA) chelators for (68)Ga and (64)Cu labeling. The conjugates were synthesized by solid-phase peptide synthesis, purified by reversed-phase high-performance liquid chromatography, and verified by liquid chromatography mass spectrometry. Saturation and competitive binding assays with B16F10 melanoma cells determined the affinity of the compounds for VLA-4. The biodistributions of the LLP2A conjugates were evaluated in murine B16F10 subcutaneous tumor-bearing C57BL/6 mice. Melanoma metastasis was induced by intracardiac injection of B16F10 cells. PET/CT imaging was performed at 2, 4, and 24 h after injection for the (64)Cu tracers and 1 h after injection for the (68)Ga tracer.

RESULTS

(64)Cu-labeled CB-TE1A1P-PEG4-LLP2A and NODAGA-PEG4-LLP2A showed high affinity to VLA-4, with a comparable dissociation constant (0.28 vs. 0.23 nM) and receptor concentration (296 vs. 243 fmol/mg). The tumor uptake at 2 h after injection was comparable for the 2 probes, but (64)Cu-CB-TE1A1P-PEG4-LLP2A trended toward higher uptake than (64)Cu-NODAGA-PEG4-LLP2A (16.9 ± 2.2 vs. 13.4 ± 1.7 percentage injected dose per gram, P = 0.07). Tumor-to-muscle and tumor-to-blood ratios from biodistribution and PET/CT images were significantly higher for (64)Cu-CB-TE1A1P-PEG4-LLP2A than (64)Cu-NODAGA-PEG4-LLP2A (all P values < 0.05). PET/CT imaging of metastatic melanoma with (68)Ga-NODAGA-PEG4-LLP2A and (64)Cu-NODAGA-PEG4-LLP2A showed high uptake of the probes at the site of metastasis, correlating with the bioluminescence imaging of the tumor.

CONCLUSION

These data demonstrate that (64)Cu-labeled CB-TE1A1P/NODAGA LLP2A conjugates and (68)Ga-labeled NODAGA-LLP2A are excellent imaging agents for melanoma and potentially other VLA-4-positive tumors. (64)Cu-CB-TE1A1P-PEG4-LLP2A had the most optimal tumor-to-nontarget tissue ratios for translation into humans as a PET imaging agent for melanoma.

Molecular networks in melanoma invasion and metastasis

Metastatic melanoma accounts for approximately 80% of skin cancer-related deaths. Up to now there has been no effective treatment for stage IV melanoma patients due to the complexity and dissemination potential of this disease. Melanomas are heterogeneous tumors in which conventional therapies fail to improve overall survival. Targeted therapies are being developed, but the final outcome can be hampered by the incomplete knowledge of the process of melanoma progression. Even if the intracellular pathways are similar, the interaction of the cells with the surrounding environment should be taken into consideration. This article seeks to highlight some of the advances in the understanding of the molecular mechanisms underlying melanoma dissemination.

Clinical significance of joint detection of CD44v6 and CD62P in nasopharyngeal carcinoma

AIM

The aim of this study was to investigate the expression and clinical prognostic significance of adhesion molecules in nasopharyngeal carcinoma (NPC) tissues and peripheral blood.

MATERIALS AND METHODS

Flow cytometry assays for the expression levels of CD44v6 and CD62P protein in peripheral blood and tissues from controls and NPC patients were performed. Clinical and pathological features were reported and analyzed, and a survival study was carried out.

RESULTS

The expression of CD44v6 and CD62P in NPC tissues and peripheral blood was higher than that of the control group (p < 0.05). Expression levels in peripheral blood of stage III/IV NPC patients was markedly higher than that of patients in stage I/II (p < 0.05), while it had no statistically significant difference in tissues (p > 0.05). The expression levels of CD44v6 and CD62P in the lymph gland metastasis and distant metastasis group were higher than groups without such metastasis (p < 0.05), and there was no statistical difference in NPC tissues (p > 0.05). The survival rates of NPC groups with low expression in the peripheral blood were higher than those of high-expression groups (p < 0.05).

CONCLUSION

Joint detection of CD44v6 and CD62P in the peripheral blood or tissues of NPC patients has diagnostic and prognostic value as a marker of poor clinical outcome.

Gene therapy for advanced melanoma: selective targeting and therapeutic nucleic acids

Despite recent advances, the treatment of malignant melanoma still results in the relapse of the disease, and second line treatment mostly fails due to the occurrence of resistance. A wide range of mutations are known to prevent effective treatment with chemotherapeutic drugs. Hence, approaches with biopharmaceuticals including proteins, like antibodies or cytokines, are applied. As an alternative, regimens with therapeutically active nucleic acids offer the possibility for highly selective cancer treatment whilst avoiding unwanted and toxic side effects. This paper gives a brief introduction into the mechanism of this devastating disease, discusses the shortcoming of current therapy approaches, and pinpoints anchor points which could be harnessed for therapeutic intervention with nucleic acids. We bring the delivery of nucleic acid nanopharmaceutics into perspective as a novel antimelanoma therapeutic approach and discuss the possibilities for melanoma specific targeting. The latest reports on preclinical and already clinical application of nucleic acids in melanoma are discussed.

The biology of brain metastasis

BACKGROUND

It is estimated that at least 200 000 cases of brain metastases occur each year in the US, which is 10 times the number of patients diagnosed with primary brain tumors. Brain metastasis is associated with poor prognosis, neurological deterioration, diminished quality of life, and extremely short survival. Favorable interactions between tumor cells and cerebral microvascular endothelial cells encourage tumor growth in the central nervous system, while tumor cell interactions with astrocytes protect brain metastases from the cytotoxic effects of chemotherapy.

CONTENT

We review the pathogenesis of brain metastasis and emphasize the contributions of microvascular endothelial cells and astrocytes to disease progression and therapeutic resistance. Animal models used to study brain metastasis are also discussed.

SUMMARY

Brain metastasis has many unmet clinical needs. There are few clinically relevant tumor models and no targeted therapies specific for brain metastases, and the mean survival for untreated patients is 5 weeks. Improved clinical outcomes are dependent on an enhanced understanding of the metastasis-initiating population of cells and the identification of microenvironmental factors that encourage disease progression in the central nervous system.

The inhibition of the integrin VLA-4 in MV3 melanoma cell binding by non-anticoagulant heparin derivatives

INTRODUCTION

The integrin VLA-4-mediated binding is important for the metastatic dissemination of melanoma cells. Recently we found that heparin possesses a binding capacity to VLA-4. This could contribute to the heparin function to attenuate metastasis in a selectin-dependent manner. Aiming to a purposive, anti-adhesive heparin application, structural requirements of heparin for VLA-4 recognition have to be elucidated.

MATERIALS AND METHODS

A series of non-anticoagulant heparin derivatives were investigated concerning their inhibitory capacities for VLA-4 mediated binding of human melanoma MV3 cells to VCAM-1 under physiological flow conditions in vitro. A surface acoustic wave biosensor was applied to detect kinetic constants of selected derivatives binding to both, VLA-4 or P- and L-selectin.

RESULTS

Experimental metastasis of MV3 cells in mice confirmed the relevance of VLA-4 for metastatic dissemination. LMWHs (enoxaparin, tinzaparin) efficiently blocked VLA-4 cell binding, dominantly via the integrin`s α-chain. Desulfation at 2-O-position, N-acetylation or a size smaller than tetradecasaccharide disfavoured VLA-4 inhibition. Glycol-splitting of heparin and thus higher chain flexibility is a tolerable parameter. A derivative with 50% 6-O-desulfation appeared promising and exceeded tinzaparin in VLA-4 inhibition, both compounds displayed binding affinities to VLA-4 in the low micromolar range.

CONCLUSIONS

These findings provide structure-activity relationships for heparin VLA-4 binding, which partly differ from P- and L-selectin requirements. The data confirm that anti-coagulative and anti-adhesive function of heparin can be distinguished favouring applications of non-anticoagulant heparins in antimetastatic approaches without the risk of bleeding complications. The 50% 6-O-desulfated heparin-derivative appears promising to further evaluate the interference with selectin and VLA-4 binding functions in vivo.

Vascular endothelial growth factor regulates melanoma cell adhesion and growth in the bone marrow microenvironment via tumor cyclooxygenase-2

BACKGROUND

Human melanoma frequently colonizes bone marrow (BM) since its earliest stage of systemic dissemination, prior to clinical metastasis occurrence. However, how melanoma cell adhesion and proliferation mechanisms are regulated within bone marrow stromal cell (BMSC) microenvironment remain unclear. Consistent with the prometastatic role of inflammatory and angiogenic factors, several studies have reported elevated levels of cyclooxygenase-2 (COX-2) in melanoma although its pathogenic role in bone marrow melanoma metastasis is unknown.

METHODS

Herein we analyzed the effect of cyclooxygenase-2 (COX-2) inhibitor celecoxib in a model of generalized BM dissemination of left cardiac ventricle-injected B16 melanoma (B16M) cells into healthy and bacterial endotoxin lipopolysaccharide (LPS)-pretreated mice to induce inflammation. In addition, B16M and human A375 melanoma (A375M) cells were exposed to conditioned media from basal and LPS-treated primary cultured murine and human BMSCs, and the contribution of COX-2 to the adhesion and proliferation of melanoma cells was also studied.

RESULTS

Mice given one single intravenous injection of LPS 6 hour prior to cancer cells significantly increased B16M metastasis in BM compared to untreated mice; however, administration of oral celecoxib reduced BM metastasis incidence and volume in healthy mice, and almost completely abrogated LPS-dependent melanoma metastases. In vitro, untreated and LPS-treated murine and human BMSC-conditioned medium (CM) increased VCAM-1-dependent BMSC adherence and proliferation of B16M and A375M cells, respectively, as compared to basal medium-treated melanoma cells. Addition of celecoxib to both B16M and A375M cells abolished adhesion and proliferation increments induced by BMSC-CM. TNFα and VEGF secretion increased in the supernatant of LPS-treated BMSCs; however, anti-VEGF neutralizing antibodies added to B16M and A375M cells prior to LPS-treated BMSC-CM resulted in a complete abrogation of both adhesion- and proliferation-stimulating effect of BMSC on melanoma cells. Conversely, recombinant VEGF increased adherence to BMSC and proliferation of both B16M and A375M cells, compared to basal medium-treated cells, while addition of celecoxib neutralized VEGF effects on melanoma. Recombinant TNFα induced B16M production of VEGF via COX-2-dependent mechanism. Moreover, exogenous PGE2 also increased B16M cell adhesion to immobilized recombinant VCAM-1.

CONCLUSIONS

We demonstrate the contribution of VEGF-induced tumor COX-2 to the regulation of adhesion- and proliferation-stimulating effects of TNFα, from endotoxin-activated bone marrow stromal cells, on VLA-4-expressing melanoma cells. These data suggest COX-2 neutralization as a potential anti-metastatic therapy in melanoma patients at high risk of systemic and bone dissemination due to intercurrent infectious and inflammatory diseases.

Transcriptional control of melanoma metastasis: the importance of the tumor microenvironment

The molecular changes associated with the transition of melanoma cells from radial growth phase (RGP) to vertical growth phase (VGP) and the metastatic phenotype are not very well defined. However, some of the genes involved in this process and their transcriptional regulation are beginning to be elucidated. For example, the switch from RGP to VGP and the metastatic phenotype is associated with loss of the AP-2α transcription factor. AP-2α regulates the expression of c-KIT, MMP-2, VEGF, and the adhesion molecule MCAM/MUC18. Recently, we reported that AP-2α also regulates two G-protein coupled receptors (GPCRs) PAR-1 and PAFR. In turn, the thrombin receptor, PAR-1, regulates the expression of the gap junction protein Connexin-43 and the tumor suppressor gene Maspin. Activation of PAR-1 also leads to overexpression and secretion of proangiogenic factors such as IL-8, uPA, VEGF, PDGF, as well certain integrins. PAR-1 also cooperates with PAFR to regulate the expression of the MCAM/MUC18 via phosphorylation of CREB. The ligands for these GPCRs, thrombin and PAF, are secreted by stromal cells, emphasizing the importance of the tumor microenvironment in melanoma metastasis. The metastatic phenotype of melanoma is also associated with overexpression and function of CREB/ATF-1. Loss of AP-2α and overexpression of CREB/ATF-1 results in the overexpression of MCAM/MUC18 which by itself contributes to melanoma metastasis by regulating the inhibitor of DNA binding-1 (Id-1). CREB/ATF-1 also regulates the angiogenic factor CYR-61. Our recent data indicate that CREB/ATF-1 regulates the expression of AP-2α, thus, supporting the notion that CREB is an important "master switch" in melanoma progression.

Biomarkers: the useful and the not so useful--an assessment of molecular prognostic markers for cutaneous melanoma

Among individuals with localized (Stage I-II) melanoma, stratifying patients by a number of phenotypic variables (e.g., depth of invasion, ulceration) yields a wide range of 10-year melanoma-specific survival rates. With the possible exception of Ki-67, no molecular assessment is routinely used. However, there have been a tremendous number of studies assessing protein expression by immunohistochemistry toward the goal of better prediction of recurrence. In a previous systematic review, which required publication of multivariable prognostic models as a strict inclusion criterion, we identified 37 manuscripts that collectively reported on 62 proteins. Data for 324 proteins extracted from 418 manuscripts did not meet our inclusion criteria for that study, but are revisited here, emphasizing trends of protein expression across either melanocytic lesion progression or gradations of tumor thickness. These identified 101 additional proteins that stratify melanoma, organized according to the Hanahan and Weinberg functional capabilities of cancer.

Constitutive expression of the alpha4 integrin correlates with tumorigenicity and lymph node metastasis of the B16 murine melanoma

The lymphatic system plays a critical role in melanoma metastasis, and yet, virtually no information exists regarding the cellular and molecular mechanisms that take place between melanoma cells and the lymphatic vasculature. Here, we generated B16-F1 melanoma cells that expressed high (B16alpha(4)+) and negligible (B16alpha(4)-) levels of alpha(4) integrin to determine how the expression of alpha(4) integrins affects tumor cell interactions with lymphatic endothelial cells in vitro and how it impacts lymphatic metastasis in vivo. We found a direct correlation between alpha(4) integrin expression on B16-F1 melanoma cells and their ability to form adhesive interactions with monolayers of lymphatic endothelial cells. Adhesion of B16-F1 melanoma cells to lymphatic endothelial cells was mediated by the melanoma cell alpha(4) integrin binding to its counterreceptor, vascular cell adhesion molecule 1 (VCAM-1), that was constitutively expressed on the lymphatic endothelial cells. VCAM-1 was also expressed on the tumor-associated lymphatic vessels of B16-F1 and B16alpha(4)+ tumors growing in the subcutaneous space of C57BL/6J mice. B16-F1 tumors metastasized to lymph nodes in 30% of mice, whereas B16alpha(4)+ tumors generated lymph node metastases in 80% of mice. B16-F1 melanoma cells that were deficient in alpha(4) integrins (B16alpha(4)-) were nontumorigenic. Collectively, these data show that the alpha(4) integrin expressed by melanoma cells contributes to tumorigenesis and may also facilitate metastasis to regional lymph nodes by promoting stable adhesion of melanoma cells to the lymphatic vasculature.

Melanoma biomarkers: current status and utility in diagnosis, prognosis, and response to therapy

Melanoma is the most devastating form of skin cancer and represents a leading cause of cancer death, particularly in young adults. As even relatively small melanomas can readily metastasize, accurate staging of progression is critical. Diagnosis is typically made on the basis of histopathologic criteria; with tumor thickness (Breslow), invasion level (Clark), ulceration, and the extent of lymph node involvement being important prognostic indicators. However, histologic criteria alone cannot diagnose all melanomas and there are often problems in distinguishing subsets of benign nevi from melanoma. There also exists a group of patients with thin primary melanomas for whom surgery should be curative but who ultimately go on to develop metastases. Therefore, there is an urgent need to develop molecular biomarkers that identify melanoma patients with high-risk primary lesions to facilitate greater surveillance and possible adjuvant therapy. The advent of large-scale genomic profiling of melanoma is revealing considerable heterogeneity, suggesting that melanomas could be subgrouped according to their patterns of oncogenic mutation and gene expression. It is hoped that this subgrouping will allow for the personalization of melanoma therapy using novel molecularly targeted agents. Much effort is now geared toward defining the genetic markers that may predict response to targeted therapy agents as well as identifying pharmacodynamic markers of therapy response. In this review, we discuss the utility of melanoma biomarkers for diagnosis and prognosis and suggest how novel molecular signatures can help guide both melanoma diagnosis and therapy selection.

Assessing tumor angiogenesis in histological samples

Tumor neovascularization acquires vessels through a number of processes, including angiogenesis, vasculogenesis, vascular remodelling, intussusception, and possibly vascular mimicry in certain tumors. The end result of the tumor vasculature has been quantified by counting the number of immunohistochemically identified microvessels in areas of maximal vascularity so-called hot spots. Other techniques have been developed, such as Chalkley counting and the use of image analysis systems that are robust and reproducible as well as more objective. Many of the molecular pathways that govern tumor neovascularization have been identified, and many reagents are now available to study these tissue sections. These include angiogenic growth factors and their receptors, cell adhesion molecules, proteases, and markers of activated, proliferating, cytokine-stimulated, or angiogenic vessels, such as CD105. It is also possible to differentiate quiescent from active vessels. Other reagents that can identify proteins involved in microenvironmental influences such as hypoxia have also been generated. Although the histological assessment of tumor vascularity is used mostly in the research context, it may also have clinical applications if appropriate methodology and trained observers perform the studies.

Targeting selectins and selectin ligands in inflammation and cancer

Inflammation and cancer metastasis are associated with extravasation of leukocytes or tumor cells from blood into tissue. Such movement is believed to follow a coordinated and sequential molecular cascade initiated, in part, by the three members of the selectin family of carbohydrate-binding proteins: E-selectin (CD62E), L-selectin (CD62L) and P-selectin (CD62P). E-selectin is particularly noteworthy in disease by virtue of its expression on activated endothelium and on bone-skin microvascular linings and for its role in cell rolling, cell signaling and chemotaxis. E-selectin, along with L- or P-selectin, mediates cell tethering and rolling interactions through the recognition of sialo-fucosylated Lewis carbohydrates expressed on structurally diverse protein-lipid ligands on circulating leukocytes or tumor cells. Major advances in understanding the role of E-selectin in inflammation and cancer have been advanced by experiments assaying E-selectin-mediated rolling of leukocytes and tumor cells under hydrodynamic shear flow, by clinical models of E-selectin-dependent inflammation, by mice deficient in E-selectin and by mice deficient in glycosyltransferases that regulate the binding activity of E-selectin ligands. Here, the authors elaborate on how E-selectin and its ligands may facilitate leukocyte or tumor cell recruitment in inflammatory and metastatic settings. Antagonists that target cellular interactions with E-selectin and other members of the selectin family, including neutralizing monoclonal antibodies, competitive ligand inhibitors or metabolic carbohydrate mimetics, exemplify a growing arsenal of potentially effective therapeutics in controlling inflammation and the metastatic behavior of cancer.

High affinity interaction of integrin alpha4beta1 (VLA-4) and vascular cell adhesion molecule 1 (VCAM-1) enhances migration of human melanoma cells across activated endothelial cell layers

The capacity of tumor cells to form metastatic foci correlates with their ability to interact with and migrate through endothelial cell layers. This process involves multiple adhesive interactions between tumor cells and the endothelium. Only little is known about the molecular nature of these interactions during extravasation of tumor cells. In human melanoma cells, the integrin alphavbeta3 is involved in transendothelial migration and its expression correlates with metastasis. However, many human melanoma cells do not express beta3 integrins. Therefore, it remained unclear how these cells undergo transendothelial migration. In this study we show that human melanoma cells with different metastatic potency, which do not express beta2 or beta3 integrins, express the VCAM-1 receptor alpha4beta1. VCAM-1 is up-regulated on activated endothelial cells and is known to promote transendothelial migration of leukocytes. Interestingly, despite comparable cell surface levels of alpha4beta1, only the highly metastatic melanoma cell lines MV3 and BLM, but not the low metastatic cell lines IF6 and 530, bind VCAM-1 with high affinity without further stimulation, and are therefore able to adhere to and migrate on isolated VCAM-1. Moreover, we demonstrate that function-blocking antibodies against the integrin alpha4beta1, as well as siRNA-mediated knock-down of the alpha4 subunit in these highly metastatic human melanoma cells reduce their transendothelial migration. These data imply that only high affinity interactions between the integrin alpha4beta1 on melanoma cells and VCAM-1 on activated endothelial cells may enhance the metastatic capacity of human beta2/beta3-negative melanoma cells.

Phosphorylation of ectopically expressed L-plastin enhances invasiveness of human melanoma cells

The leukocyte specific actin-binding protein L-plastin is aberrantly expressed in several nonhematopoetic malignant tumors. However, little is known about the functional consequences of L-plastin expression. Here, we investigated the function of L-plastin in human malignant melanoma cells. Knock-down of endogenous L-plastin by siRNA treatment reduced migration of the melanoma cell line IF6. However, in melanoma patients, no correlation existed between L-plastin expression and tumor stages. This implied that additional factors such as phosphorylation of L-plastin may influence its function in tumor cells. To investigate this further, EGFP-tagged wild-type L-plastin (wt-LPL-EGFP) and a mutated, nonphosphorylatable L-plastin protein (5A7A-LPL-EGFP), were expressed in the L-plastin negative melanoma cell line MV3. Biochemical analysis revealed that wt-LPL-EGFP is phosphorylated in MV3 cells while 5A7A-LPL-EGFP is not. Although both wt-LPL-EGFP and 5A7A-LPL-EGFP were targeted to, and promote the formation of, vinculin-containing adhesion sites, static adhesion to either Matrigel or isolated extracellular matrix molecules was neither influenced by expression of wt-LPL-EGFP nor by expression of 5A7A-LPL-EGFP when compared with EGFP expressing control cells. In contrast, haptotactic, but not chemotactic, migration of melanoma cells towards either Matrigel or isolated extracellular matrix molecules was similarly enhanced, if either 5A7A-LPL-EGFP or wt-LPL-EGFP were expressed in MV3 cells. Interestingly, only cells expressing the phosphorylatable wt-LPL-EGFP protein showed enhanced invasion into Matrigel. In line with these findings the in vivo metastatic capacity of mouse B16 melanoma cells correlates with expression and phosphorylation of L-plastin. These data show that an increase in melanoma cell invasiveness requires not only expression but also phosphorylation of L-plastin.

Tumor cell-organ microenvironment interactions in the pathogenesis of cancer metastasis

The process of cancer metastasis is sequential and selective and contains stochastic elements. The growth of metastases represents the endpoint of many lethal events that few tumor cells can survive. Primary tumors consist of multiple subpopulations of cells with heterogeneous metastatic properties, and the outcome of metastasis depends on the interplay of tumor cells with various host factors. The findings that different metastases can originate from different progenitor cells account for the biological diversity that exists among various metastases. Even within a solitary metastasis of proven clonal origin, however, heterogeneity of biological characteristics can develop rapidly. The pathogenesis of metastasis depends on multiple interactions of metastatic cells with favorable host homeostatic mechanisms. Interruption of one or more of these interactions can lead to the inhibition or eradication of cancer metastasis. For many years, all of our efforts to treat cancer have concentrated on the inhibition or destruction of tumor cells. Strategies both to treat tumor cells (such as chemotherapy and immunotherapy) and to modulate the host microenvironment (including the tumor vasculature) should offer additional approaches for cancer treatment. The recent advances in our understanding of the biological basis of cancer metastasis present unprecedented possibilities for translating basic research to the clinical reality of cancer treatment.

Adhesion, migration and communication in melanocytes and melanoma

Under normal conditions, homeostasis determines whether a cell remains quiescent, proliferates, differentiates, or undergoes apoptosis. In this state of homeostasis, keratinocytes control melanocyte growth and behaviour through a complex system of paracrine growth factors and cell-cell adhesion molecules. Alteration of this delicate homeostatic balance and can lead to altered expression of cell-cell adhesion and cell communication molecules and to the development of melanoma. Melanoma cells escape from this control by keratinocytes through three major mechanisms: (1) down-regulation of receptors important for communication with keratinocytes such as E-cadherin, P-cadherin, desmoglein and connexins, which is achieved through growth factors produced by fibroblasts or keratinocytes; (2) up-regulation of receptors and signalling molecules not found on melanocytes but important for melanoma-melanoma and melanoma-fibroblast interactions such as N-cadherin, Mel-CAM, and zonula occludens protein-1 (ZO-1); (3) loss of anchorage to the basement membrane because of an altered expression of the extracellular-matrix binding integrin family. In the current review, we describe the alterations in cell-cell adhesion and communication associated with melanoma development and progression, and discuss how a greater understanding of these processes may aid the future therapy of this disease.

Histological quantitation of tumour angiogenesis

Tumours establish their blood supply via a number of processes in addition to angiogenesis. These include vasculogenesis, vascular remodelling, intussusception and possibly vascular mimicry in certain tumours. The mainstay of the assessment of tumour vascularity has been counting the number of immunohistochemically identified microvessels in vascular hot spots. Nevertheless, several other techniques are available, including Chalkley counting, vascular grade and the use of image analysis systems. Angiogenic activity can furthermore be assessed in histological samples by measuring the molecules involved in the establishment of the tumour vasculature, including angiogenic growth factors and their receptors, cell adhesion molecules, proteases and markers of activated, proliferating, cytokine stimulated or angiogenic vessels, such as CD105. Measuring the maturity of vessels may give an indication of the proportion of the tumour vasculature that is functional. Other reagents that can identify hypoxia-activated pathways are also being developed. The histological assessment of tumour vascularity is mainly used in the research setting but may also have applications in the clinic if appropriate methodology and trained observers perform the studies. Gene arrays may be able to provide an angiogenesis profile. Continued study into the processes involved in generating a tumour blood supply is likely to identify new markers that may be more accurate measures.

Interactions between cancer cells and the endothelium in metastasis

The haematogenous phase of cancer metastasis facilitates the transport of metastatic cells within the blood and incorporates a sequence of interactions between circulating intravascular cancer cells and the endothelium of blood vessels at the sites of tumour cell arrest. Initial interactions involve mechanical contact and transient adhesion, mediated by endothelial selectins and their ligands on the neoplastic cells. This contact initiates a sequence of activation pathways that involves cytokines, growth factors, bioactive lipids, and reactive oxygen species produced by either the cancer cell or the endothelium. These molecules elicit expression of integrin adhesion molecules in cancer cells and the endothelium, matrix metalloproteinases, and chemotactic factors that promote the attachment of tumour cells to the vessel wall and/or transvascular penetration. Induction of endothelial free radicals can be cytotoxic to cancer cells. Collectively, the sum of these interactions constitutes an interdependent relationship, the outcome of which determines the fate of the metastatic process.

Serum levels of the soluble adhesion molecules in patients with malignant melanoma

The incidence of malignant melanoma has been steadily increasing over the past decades. CD 44 is a transmembrane glycoprotein which is implicated in a number of adhesive and migratory events. Downregulation of CD 44 is implicated in the metastatic process. P-Selectin is a member of the selectin family of cell surface molecules. The levels of P-Selectin in biological fluids may be elevated in subjects with a variety of pathological conditions. In malignant melanoma, elevation of the plasma level of soluble intercellular adhesion molecule-1 (sICAM-1) has been associated with a reduction in disease-free survival. This study was performed to investigate the differences in the serum concentrations of the adhesion molecules in patients with malignant melanoma. The study group consisted of 52 patients with malignant melanoma and 20 healthy subjects. No meaningful difference was observed for P-selectin and sICAM 1 levels. A statistically significant decrease was observed in the cancer patients for serum CD 44 levels.

Are selectins involved in metastasis?

The selectins are a family of intercellular adhesion molecules that mediate the attachment of leukocytes to the endothelial lining of blood vessels. Another biological process that may involve selectins is the adhesion of circulating tumour cells to endothelium in cancer metastasis. This review discusses the evidence for the involvement of E-, P- and L-selectin in the metastasis of different tumour types. It is concluded that, with certain reservations and qualifications, selectins can play a role in metastasis. For example, the evidence for the involvement of E-selectin in breast and colon cancer metastasis is very strong. For the other selectins and tumour types the evidence is less convincing and further investigations are required to clarify the situation. Certainly, selectins are not the only mechanism available for tumours to metastasise. In the future, measurement of selectins could be useful prognostically and manipulation of their levels could lead to new cancer therapies.

Molecular prognostic markers in intermediate-thickness cutaneous malignant melanoma

BACKGROUND

The limitations of morphologic criteria alone in determining the prognosis for a patient with a particular intermediate-thickness primary melanoma have prompted efforts to identify other markers.

METHODS

In this study, the authors analyzed expression of p53, beta1 integrin, and beta3 integrin in primary tumors from 111 patients with intermediate-thickness malignant melanoma.

RESULTS

Eighty-nine (80%) had detectable p53 protein, 58 (52%) expressed beta1 integrin, and 71 (64%) expressed beta3 integrin. Patients with beta3 positive melanomas were more likely to die of their disease (32 of 71 patients, 45%) than those with beta3 negative tumors (3 of 40 patients, 8%) (P < 0.0001). The number of involved lymph nodes, Clark's level, beta1 integrin expression, thickness, and mitotic rate also had prognostic significance. beta3 integrin was associated with subsequent lung metastases and beta1 integrin with lymph node involvement.

CONCLUSIONS

Integrin expression, along with histopathologic criteria, is a prognostic marker for intermediate-thickness malignant melanoma and may indicate the site of subsequent metastasis. These observations may have clinical utility and suggest areas for future investigation.

Markers of melanocytic tumour progression

Melanoma progression markers can be defined as molecules with a preferential expression in one or a few stages of melanocytic tumour development. These molecules include growth factors, growth factors receptors, adhesion molecules, proteases and related components. Immunohistochemical studies suggest that some of these molecules are useful as prognostic markers in melanoma patients. In cutaneous melanocytic lesions, the distribution of E-cadherin, a member of a family of cell adhesion molecules that mediate cell-cell interactions by means of Ca2+ dependent, homophilic interactions, appears to be complex. Although a decrease of E-cadherin would be expected with invasive tumour growth in advanced primary melanoma and eventually in metastasis, surprisingly an increase is found, whereas alpha- and beta-catenin, (cytoplasmic) molecules functionally associated with E-cadherin, are detected in all benign and malignant lesions. A possible interpretation includes a difference in the morphogenesis and function of melanocytic cells, compared with epithelial cells. Further research is needed to clarify the role of E-cadherin/catenin during melanoma progression.

Prognosis in malignant melanoma

A uniform and practical classification and staging system for melanoma must exist and be widely adopted if useful comparisons between different treatment centers and databases are to be made. This article reviews the 1992 American Joint Committee on Cancer pTNM staging system. In this classification, localized disease without regional nodal involvement is defined as stage I or II, depending on the tumor thickness of the primary melanoma. Regional lymph node involvement and/or in-transit metastasis is defined as stage III, and systemic metastatic disease is defined as stage IV.

Elevated pretreatment serum levels of soluble vascular cell adhesion molecule 1 and lactate dehydrogenase as predictors of survival in cutaneous metastatic malignant melanoma

Very rapid progression of disease with a median survival of 6-9 months is a common feature of metastatic cutaneous malignant melanoma. Nevertheless, substantial variability of survival suggests that metastatic cutaneous malignant melanoma can be divided into several biological subgroups. Pretreatment serum levels of soluble adhesion molecules and various clinical parameters in cutaneous metastatic malignant melanoma were evaluated to determine their prognostic value. In this study pretreatment serum levels of soluble vascular cell adhesion molecule 1 (sVCAM-1), soluble intercellular cell adhesion molecule 1 (sICAM-1), soluble endothelial leukocyte adhesion molecule 1 (sE-selectin) and multiple clinical factors were assessed in relation to overall survival of 97 consecutive patients with metastatic cutaneous malignant melanoma seen at our institution between May 1990 and April 1996. For statistical analysis, both univariate and multivariate Cox proportional-hazards models were used. Elevated pretreatment serum levels of sVCAM-1 (P < 0.005) and of lactate dehydrogenase (P < 0.002) were rendered statistically independent and were significantly associated with unfavourable outcome. Patients were assigned to one of three risk categories (low, intermediate and high) according to a cumulative risk score defined as the function of the sum of these two variables. There were significant differences in overall survival (P < 0.0001) between low- (n = 53, 5-year survival probability of 23.3%), intermediate- (n = 29, 5-year survival probability of 9.9%) and high-risk (n = 15) patients. Elevated pretreatment serum levels of sVCAM-1 and of lactate dehydrogenase correlate with poor outcome in metastatic cutaneous malignant melanoma. These data support risk stratification for future therapeutic trials and identify factors that need to be validated in prospective studies and may potentially influence decision-making in palliative management of patients with disseminated cutaneous malignant melanoma.

The disintegrin eristostatin interferes with integrin alpha 4 beta 1 function and with experimental metastasis of human melanoma cells

Peptides containing the integrin recognition sequence, RGD, can inhibit experimental metastasis of mouse melanoma cells, but the integrin(s) affected in these experiments is unknown. Besides "classical" RGD-binding integrins such as alpha 5 beta 1 and alpha v beta 3, RGD has been reported to bind alpha 4 beta 1, and mAbs to alpha 4 beta 1 can inhibit melanoma metastasis. We investigated the mode of action of the disintegrin eristostatin, an RGD-containing peptide isolated from snake venom, in a human melanoma experimental metastasis model. Lung colonization following i.v. injection of MV3 cells in nude mice was strongly inhibited by eristostatin. MV3 cells bound FITC-eristostatin and adhered to eristostatin-coated wells. This adhesion was partially inhibited by a GRGDSP peptide and by alpha 4 mAb. Binding of FITC-eristostatin to Jurkat cells and adhesion of Jurkat (but not K562) cells to eristostatin-coated wells further suggested that eristostatin binds alpha 4 beta 1, even though, again, alpha 4 mAb only partially inhibited adhesion. Expression of alpha 4 beta 1 was enhanced in metastatic melanoma cells compared to normal melanocytes and nonmetastatic melanoma cells. Finally, eristostatin inhibited adhesion of both MV3 and CHO alpha 4 cells to the alpha 4 beta 1-ligand VCAM-1, while adhesion to other ligands via other integrins was not affected. These findings demonstrate that inhibition of melanoma cell metastasis by RGD-containing peptides such as eristostatin, may be due to interference with alpha 4 beta 1-VCAM binding, in addition to inhibition of the classical RGD-binding integrins.

Activation status and function of the VLA-4 (alpha4beta1) integrin expressed on human melanoma cell lines

We have examined the functional status of the VLA-4/alpha4beta1 integrin in a panel of human melanoma cell lines, focusing on the ability of cells expressing alpha4beta1 to mediate adhesion to the alpha4-specific ligands CS-1 peptide and VCAM-1. All melanoma cells expressing alpha4pbeta1 (8 of 10 lines examined) were capable of adhering to these specific ligands in adhesion assays, whereas 2 cell lines (HMB2 and VUP) which lacked surface alpha4 were unable to do so. Adherence of different melanoma cell lines to VCAM-1 was relatively uniform and not susceptible to upregulation with known integrin-activating factors, such as manganese ions, phorbol ester and activating monoclonal antibody (mAb) TS2/16. Cell adhesion to CS-1 peptide, however, varied according to cell surface receptor density and, in some cases, could be up-regulated by integrin-activating factors. Adhesion of SK23 cells to CS-1 peptide was increased by all 3 activating stimuli, whereas for all other melanoma cells an increase was obtained only by the use of TS2/16 mAb. Our data indicate not only an unusually low activation state of alpha4beta1 in SK23 cells but also heterogeneity in the activating capacity of the various stimuli. Moreover, a protein kinase C-dependent role in alpha4beta1 activity was suggested by adhesion assays carried out in the presence of the protein kinase C inhibitor calphostin C, which considerably reduced adhesion to CS-1 peptide.