Angiogenesis in cutaneous melanoma: pathogenesis and clinical implications

Anti-angiogenesis Revisited: Combination with Immunotherapy in Solid Tumors

PURPOSE OF REVIEW

Both anti-angiogenesis and immunotherapy are well-established therapeutic options in solid tumors. Here, we review the rationale as well as clinical evidence of combining these two approaches.

RECENT FINDINGS

There is strong rationale and substantial preclinical and clinical evidence that anti-angiogenesis plays a pivotal role in overcoming immunotherapy resistance. The combination of an anti-angiogenic agent and a checkpoint inhibitor offers a more robust treatment option in many clinical trials in a wide variety of solid tumor types. Combination of anti-angiogenesis and immunotherapy has emerged as a standard of care in some tumor types and the indication is expected to expand to more tumor types in the years to come.

Targeted drug delivery to melanoma

Melanoma derived from melanocytes is the most aggressive genre of skin cancer. Although the considerable advancement in the study of human cancer biology and drug discovery, most advanced melanoma patients are inevitably unable to be cured. With the emergence of nanotechnology, the use of nano-carriers is widely expected to alter the landscape of melanoma treatment. In this review, we will discuss melanoma biology, current treatment options, mechanisms behind drug resistance, and nano-based solutions for effective anti-cancer therapy, followed by challenges and perspectives in both pre-clinical and clinical settings.

Immunohistochemical Expression of Vascular Endothelial Growth Factor (VEGF) and C-KIT in Cutaneous Melanocytic Lesions

Vascular endothelial growth factor (VEGF) and C-KIT are involved in tumor progression in several human neoplasms. The aim of the present study has been to investigate their immunohistochemical expression in melanocytic lesions. We examined 11 compound nevi, 12 dysplastic nevi, and 18 melanomas. Immunostaining for VEGF was observed only in melanomas; c-kit expression was detected in melanomas (higher in radial than in vertical growth phase) and in nevi (predominantly in the junctional component). Our data indicate that assessment of VEGF expression might aid in the differential diagnosis between dysplastic nevi and melanomas. Moreover, VEGF might be a candidate for targeted therapy. The loss of c-kit expression might contribute to melanoma progression.

Toward in vivo biopsy of melanoma based on photoacoustic and ultrasound dual imaging with an integrated detector

Melanoma is the most dangerous type of skin cancer with high lethal rate. Tumor thickness and tumor-associated vasculature are two key parameters for staging melanoma. Previous techniques for diagnosing melanoma have insurmountable restrictions, such as invasive, low specificity, or inaccurate depth measurement. Here we develop an integrated photoacoustic (PA) and ultrasound (US) imaging system dedicated to overcome these limitations. An integrated detector with sound-light coaxial/confocal design and flexible coupling mode is employed for the combined PA/US imaging strategy. PA imaging results enable a clear characterization of tumor angiogenesis with high resolution and high contrast. Furthermore, accurate thickness measurements of melanoma in different stages can be resolved with the simultaneously obtained PA/US image. Phantom experiments and in vivo animal experimental results demonstrate the integrated PA/US system could provide potential for noninvasive biopsy of melanoma.

Assessment of vascularity in common blue nevi, small/medium congenital nevocellular, common and dysplastic acquired melanocytic nevi and melanomas: a comparative study

Angiogenesis and vascularity are researched in melanocytic tumors for their importance in carcinogenesis. For the first time, to the best of our knowledge, the authors compared the microvascular characteristics between small/medium congenital nevocellular nevi (CN), common blue nevi (BN), common and dysplastic acquired melanocytic nevi (AMN), and melanomas. The authors collected 31 BN, 48 CN (≤5 cm), 35 AMN (14 common, 21 dysplastic), and 26 melanomas. Vessels were stained with factor VIII. Microvascular density (MVD) and total vascular area (TVA), where evaluated in high capillary density areas. Student t and Mann-Whitney tests were used. MVD (mean ± SD) was low in BN (3.52 ± 1.21) and significantly higher in CN (7.56 ± 2.47) (P < 0.001). TVA was low in BN and significantly higher in CN (Mann-Whitney U = 141, n1 = 48, n2 = 31, P < 0.001, 2-tailed). MVD was not significantly different between common and dysplastic AMN (20.64 ± 7.87 and 20.38 ± 9.54, respectively) (P > 0.05). TVA was not significantly different between common and dysplastic AMN (Mann-Whitney U = 164, n1 = 14, n2 = 21, P > 0.05, 2-tailed). MVD was significantly lower in CN (7.56 ± 2.47) compared with AMN (20.49 ± 8.79) (P < 0.001). TVA was significantly lower in CN compared with AMN (Mann-Whitney U = 1486, n1 = 48, n2 = 35, P < 0.001, 2-tailed). MVD was significantly lower in AMN (20.49 ± 8.79) compared with melanomas (33.77 ± 14.32) (P < 0.001). TVA (mean ± SD) was significantly smaller in AMN (18473.94 ± 7050.61) compared with melanomas (29308.50 ± 11307.22) (P < 0.001). Vascularity increased from BN to CN to AMN with melanomas being the most vascular. Common and dysplastic AMN had comparable vascularity. The implications of our results regarding melanoma transformation risk are considered.

Advances in the management of melanoma: targeted therapy, immunotherapy and future directions

Metastatic melanoma is an aggressive, immunogenic and molecularly heterogeneous disease for which most patients require systemic treatment. Recently, significant clinical breakthroughs have revolutionized the treatment of advanced melanoma, leading to the licensing of ipilimumab, a monoclonal antibody targeting cytotoxic T-lymphocyte-associated antigen 4, and vemurafenib, a BRAF inhibitor used in patients whose tumors contain a V600 mutation in the BRAF gene. This recent success has led to optimism and momentum has gathered with updated trial results from these therapies, next-generation compounds that target validated molecular pathways and novel agents that are mechanistically distinct. This review summarizes the recent advances and updated results since the licensing of vemurafenib and ipilimumab, the benefits and limitations of these agents, future strategies to improve upon existing treatments and overcome acquired resistance, in-progress and future clinical trials, as well as novel therapeutic targets, pathways and therapies that hold promise in advancing clinical benefit.

The Roles of Angiogenesis in Malignant Melanoma: Trends in Basic Science Research over the Last 100 Years

Blood vessels arose during evolution carrying oxygen and nutrients to distant organs via complex networks of blood vessels penetrating organs and tissues. Mammalian cells require oxygen and nutrients for survival, of which oxygen has a diffusion limit of 100 to 200 μm between cell and blood vessel. For growth beyond this margin, cells must recruit new blood vessels, first by vasculogenesis, where embryonic vessels form from endothelial precursors, then angiogenesis which is the sprouting of interstitial tissue columns into the lumen of preexisting blood vessels. Angiogenesis occurs in many inflammatory diseases and in many malignant disease states, including over 90% of solid tumours. Malignant melanoma (MM) is the most lethal skin cancer, highly angiogenic, highly metastatic, and refractory to all treatments. Raised serum levels of vascular endothelial growth factor (VEGF) strongly correlate MM disease progression and poor prognosis. Melanoma cells secrete several proangiogenic cytokines including VEGF-A, fibroblast growth factor (FGF-2), platelet growth factor (PGF-1), interleukin-8 (IL-8), and transforming growth factor (TGF-1) that modulate the angiogenic switch, changing expression levels during tumour transition from radial to invasive vertical and then metastatic growth. We highlight modern and historical lines of research and development that are driving this exciting area of research currently.

Therapy for metastatic melanoma: the past, present, and future

Metastatic melanoma is the most aggressive form of skin cancer with a median overall survival of less than one year. Advancements in our understanding of how melanoma evades the immune system as well as the recognition that melanoma is a molecularly heterogeneous disease have led to major improvements in the treatment of patients with metastatic melanoma. In 2011, the US Food and Drug Administration (FDA) approved two novel therapies for advanced melanoma: a BRAF inhibitor, vemurafenib, and an immune stimulatory agent, ipilimumab. The success of these agents has injected excitement and hope into patients and clinicians and, while these therapies have their limitations, they will likely provide excellent building blocks for the next generation of therapies. In this review we will discuss the advantages and limitations of the two new approved agents, current clinical trials designed to overcome these limitations, and future clinical trials that we feel hold the most promise.

A pilot study of bevacizumab and interferon-α2b in ocular melanoma

OBJECTIVES

We hypothesized that administration of bevacizumab, a monoclonal antibody that neutralizes vascular endothelial growth factor, in combination with high-dose interferon-alpha2b (IFN-α2b), an inhibitor of basic fibroblast growth factor, would have clinical activity in patients with metastatic ocular melanoma.

METHODS

Patients with metastatic ocular melanoma received bevacizumab (15 mg/kg intravenously every 2 weeks) plus IFN-α2b (5 MU/m subcutaneously 3 times weekly for 2 weeks followed by a dose of 10 MU/m subcutaneously thereafter). Patients exhibiting a clinical response or stabilization of disease were treated until disease progression.

RESULTS

In this pilot study, 5 patients were treated (3 men, 2 women) with a mean age of 63.8 years (range, 53-71 years). Overall, the regimen was well-tolerated. The following adverse events were noted: grade 3 dyspnea (2 patients), grade 3 and 4 fatigue (2), grade 3 muscle weakness (1), grade 3 anorexia (1), grade 1 and 2 proteinuria (2), and grade 3 diarrhea (1). All adverse events resolved with a treatment holiday or dose reduction. One patient had reduction in tumor burden of 23% by Response Evaluation Criteria in Solid Tumors criteria and 2 patients had stabilization of disease lasting 28 and 36 weeks, respectively. Two patients failed to respond and progressed after 6 and 7 weeks of therapy.

CONCLUSION

Bevacizumab and IFN-α2b were well tolerated in this patient population, and clinical activity was observed. Further study of high-dose IFN-α2b in combination with bevacizumab in this setting is warranted.

A novel histochemical method for a simultaneous staining of melanin and collagen fibers

For the histopathologic diagnosis of melanocytic lesions, it could be necessary to identify the melanin pigment because its visualization is unspecific with hematoxylin-eosin (HE). The Fontana-Masson (FM) technique is used in histopathology in this type of lesion, which allows the identification of the pigment, but it loses all the morphologic parameters. The authors describe a modification to the FM method, for the evaluation of the morphology, the argentaffin reaction of the melanin, and collagens fibers of the extracellular matrix simultaneously, for which they have developed the Fontana-Masson picrosirius (FMPS) method. Biopsies of different melanocytic lesions were used for the performance of the HE, FM, and FMPS methods. The pixel intensity of the reaction for melanin, collagen, and epithelium was determined with ImageJ software. The FMPS method allows the evaluation of morphological characteristics, identifying the melanin pigment and collagen fibers with high intensity simultaneously. This method does not differ significantly from FM in the identification of melanin, maintaining its sensitivity and specificity. In addition, it does not differ in the demonstration of the morphology with HE. However, FMPS is significantly superior in the identification of collagen fibers. The FMPS method combines morphological and histochemical parameters that could be useful in the study of pigmented lesions of melanocytic origin.

Dual targeting of tumor and endothelial cells by gonadotropin-releasing hormone agonists to reduce melanoma angiogenesis

We showed previously that GnRH receptors are expressed in melanoma cells; their activation reduces cell growth and metastatic behavior. Here, we investigated whether GnRH agonists might affect the expression of genes involved in melanoma progression. By genome-wide transcriptomic and real-time PCR analysis, we first observed that GnRH agonists decrease the expression of the pro-angiogenic factor vascular endothelial growth factor (VEGF) (all isoforms) in BLM melanoma cells. Then, we demonstrated that GnRH agonists specifically decrease the expression of the VEGF165 isoform as well as its secretion from BLM cells. These data suggested that activation of GnRH receptors might reduce the pro-angiogenic behavior of melanoma cells. To verify this hypothesis, we treated BLM cells with a GnRH agonist; the conditioned medium from these cells was tested to assess its capability to stimulate human umbilical vein endothelial cell (HUVEC) motility. The migration of HUVECs towards the conditioned medium of GnRH agonist-treated BLM cells was significantly lower than the migration of HUVECs toward the conditioned medium of untreated cells. Thus, GnRH agonists reduce the pro-angiogenic behavior of melanoma cells through a decreased production of bioactive VEGF. We then found that GnRH receptors are also expressed on HUVECs and that GnRH agonists reduce their ability to proliferate and to form capillary-like tubes when stimulated by VEGF. These findings suggest that GnRH agonists exert an anti-angiogenic activity indirectly by decreasing VEGF secretion from tumor cells and directly by counteracting the pro-angiogenic activity of the growth factor. These data might lead to the development of novel targeted approaches for melanoma.

In vivo molecular photoacoustic tomography of melanomas targeted by bioconjugated gold nanocages

Early diagnosis, accurate staging, and image-guided resection of melanomas remain crucial clinical objectives for improving patient survival and treatment outcomes. Conventional techniques cannot meet this demand because of the low sensitivity, low specificity, poor spatial resolution, shallow penetration, and/or ionizing radiation. Here we overcome such limitations by combining high-resolution photoacoustic tomography (PAT) with extraordinarily optical absorbing gold nanocages (AuNCs). When bioconjugated with [Nle(4),D-Phe(7)]-alpha-melanocyte-stimulating hormone, the AuNCs can serve as a novel contrast agent for in vivo molecular PAT of melanomas with both exquisite sensitivity and high specificity. The bioconjugated AuNCs enhanced contrast approximately 300% more than the control, PEGylated AuNCs. The in vivo PAT quantification of the amount of AuNCs accumulated in melanomas was further validated with inductively coupled plasma mass spectrometry (ICP-MS).

Mechanism of dihydrofolate reductase downregulation in melanoma by 3-O-(3,4,5-trimethoxybenzoyl)-(-)-epicatechin

In our search to improve the stability and cellular absorption of tea polyphenols, we synthesized 3-O-(3,4,5-trimethoxybenzoyl)-(-)-epicatechin (TMECG), which showed high antiproliferative activity against melanoma. TMECG downregulates dihydrofolate reductase (DHFR) expression in melanoma cells and we detail the sequential mechanisms that result from this even. TMECG is specifically activated in melanoma cells to form a stable quinone methide (TMECG-QM). TMECG-QM has a dual action on these cells. First, it acts as a potent antifolate compound, disrupting folate metabolism and increasing intracellular oxidized folate coenzymes, such as dihydrofolate, which is a non-competitive inhibitor of dihydropterine reductase, an enzyme essential for tetrahydrobiopterin (H(4)B) recycling. Such inhibition results in H(4)B deficiency, endothelial nitric oxide synthase (eNOS) uncoupling and superoxide production. Second, TMECG-QM acts as an efficient superoxide scavenger and promotes intra-cellular H(2)O(2) accumulation. Here, we present evidence that TMECG markedly reduces melanoma H(4)B and NO bioavailability and that TMECG action is abolished by the eNOS inhibitor N(omega)-nitro-L-arginine methyl ester or the H(2)O(2) scavenger catalase, which strongly suggests H(2)O(2)-dependent DHFR downregulation. In addition, the data presented here indicate that the simultaneous targeting of important pathways for melanoma survival, such as the folate cycle, H(4)B recycling, and the eNOS reaction, could represent an attractive strategy for fighting this malignant skin pathology.

Tumor-immune interaction, surgical treatment, and cancer recurrence in a mathematical model of melanoma

Malignant melanoma is a cancer of the skin arising in the melanocytes. We present a mathematical model of melanoma invasion into healthy tissue with an immune response. We use this model as a framework with which to investigate primary tumor invasion and treatment by surgical excision. We observe that the presence of immune cells can destroy tumors, hold them to minimal expansion, or, through the production of angiogenic factors, induce tumorigenic expansion. We also find that the tumor–immune system dynamic is critically important in determining the likelihood and extent of tumor regrowth following resection. We find that small metastatic lesions distal to the primary tumor mass can be held to a minimal size via the immune interaction with the larger primary tumor. Numerical experiments further suggest that metastatic disease is optimally suppressed by immune activation when the primary tumor is moderately, rather than minimally, metastatic. Furthermore, satellite lesions can become aggressively tumorigenic upon removal of the primary tumor and its associated immune tissue. This can lead to recurrence where total cancer mass increases more quickly than in primary tumor invasion, representing a clinically more dangerous disease state. These results are in line with clinical case studies involving resection of a primary melanoma followed by recurrence in local metastases.

Melanoma is a deadly skin cancer that invades into the dermis and metastasizes into the surrounding tissue. In clinical cases, surgical excision of the primary tumor has led to widespread and accelerated growth in metastases. We develop a mathematical model describing the basic process of melanoma invasion, metastatic spread, and the anti-tumor immune response. This model is formulated using partial differential equations that describe the spatial and temporal evolution of a number of different cellular populations, and it uses a realistic skin geometry. Using simulations, we examine the importance of the immune response when a primary tumor is spawning satellite metastases. We find that local metastases can be suppressed by the immune response directed against the primary tumor, but grow aggressively following surgical treatment. We also find that moderately metastatic tumors optimally activate the local immune response against disseminated disease, and in this case tumor excision may have profound effects on metastatic growth. We conclude that surgical perturbation of the immune response controlling local metastases is one mechanism by which cancer can recur. This could have implications as to the appropriate clinical management of melanomas and other solid tumors.

Phase 2 trial of carboplatin, weekly paclitaxel, and biweekly bevacizumab in patients with unresectable stage IV melanoma: a North Central Cancer Treatment Group study, N047A

BACKGROUND

Vascular endothelial growth factor (VEGF) plays an important role in the growth and metastatic progression of melanoma. Exposure of melanoma cells to chemotherapy induces VEGF overproduction, which in turn may allow melanoma cells to evade cell death and become chemotherapy resistant. Therefore, in patients with metastatic melanoma, the combination of chemotherapy with an agent that specifically targets VEGF might be able to control tumor growth and progression more effectively than chemotherapy alone.

METHODS

A 2-stage phase 2 clinical trial was conducted in patients with unresectable stage IV (metastatic) melanoma to assess antitumor activity and the toxicity profile of the combination of carboplatin (area under the curve 6 iv on Day 1 of a 28-day cycle), paclitaxel (80 mg/m2 iv on Days 1, 8, and 15), and bevacizumab (10 mg/kg iv on Days 1 and 15). Treatment was continued until progression or intolerable toxicity.

RESULTS

Fifty-three patients (62.3% male) were enrolled. Nine (17%) patients achieved partial remission, and another 30 (57%) achieved stable disease for at least 8 weeks. Median progression-free survival and median overall survival were 6 months and 12 months, respectively. One patient died after 8 treatment cycles from intracranial hemorrhage into undiagnosed brain metastases. The most common severe (grade>or=3) toxicities were neutropenia (53%), thrombocytopenia (11%), hypertension (9%), and anemia (8%).

CONCLUSIONS

This combination of carboplatin, paclitaxel, and bevacizumab appears to be moderately well tolerated and clinically beneficial in patients with metastatic melanoma. Further study of this combination is warranted.

VEGF secretion is inhibited by interferon-alpha in several melanoma cell lines

Interferon-alpha (IFN-alpha) is employed in the treatment of malignant melanoma; however, it mediates regression of disease in only 10-15% of patients. Currently, its mechanism of action is uncharacterized. Low-dose IFN-alpha exerts anti-angiogenic effects when used in the treatment of life-threatening hemangiomas of infancy, suggesting anti-angiogenesis as a mechanism of action. IFN-alpha may exert its anti-tumor effect in the setting of advanced malignancy by inhibiting the secretion of vascular endothelial growth factor (VEGF), a pro-angiogenic substance. We hypothesized that IFN-alpha would decrease the release of VEGF by melanoma tumors. We studied the effect of IFN-alpha on VEGF production in nine human melanoma cell lines. We also examined VEGF levels in 49 patients with advanced malignancies who received low-dose IFN-alpha and interleukin-12 (IL-12) on an NCI-sponsored phase I trial. Human melanoma cell lines produced varying amounts of VEGF in vitro (60-1500 pg/mL at 48 h). Certain melanoma cell lines such as 18105 MEL secreted low levels of VEGF (152 pg/mL) after 48 h of culture, whereas other lines secreted very high levels (FO-1 3,802 pg/mL). Treatment of melanoma cells with IFN-alpha (2000 U/mL) decreased VEGF secretion by 40-60% in VEGF-high cell lines; however, this effect was not demonstrated in VEGF-low cell lines. In cancer patients, pretreatment VEGF plasma levels varied from 471 to 4200 pg/mL. A decrease in VEGF plasma levels after treatment directly correlated with the number of treatment cycles administered (Pearson correlation, p = 0.04). In summary, IFN-alpha inhibits VEGF secretion by melanoma cell lines in vitro and may have similar actions in malignancies that respond to IFN-alpha treatment.

A phase II study of ABT-510 (thrombospondin-1 analog) for the treatment of metastatic melanoma

OBJECTIVES

Thrombospondins are natural inhibitors of angiogenesis, tumor metastases, and tumor growth (melanoma). ABT-510 is a synthetic analog of thrombospondin-1, well tolerated in phase I studies. We conducted a phase II trial evaluating the clinical efficacy of ABT-510 and its effects on biomarkers of angiogenesis and immunity in patients with metastatic melanoma (MM).

PATIENTS AND METHODS

A 2-stage phase II clinical trial was conducted to assess the clinical efficacy, safety, and pharmacodynamic effects (angiogenesis and immunity) of ABT-510 in patients with stage IV melanoma. The primary endpoint was 18-week treatment failure rate. Patients self-administered 100 mg of ABT-510 subcutaneously twice daily. Blood samples were collected at baseline and every 3 weeks while on therapy. Eligible patients demonstrated measurable disease, good performance status and no evidence of intracranial metastases. Correlative laboratory studies evaluated biomarkers of angiogenesis and immunity.

RESULTS

Twenty-one patients were enrolled. Most patients were stage M1c (71%) and all had prior therapy for MM. Only 3 of the first 20 patients enrolled were progression free and on treatment at 18 weeks resulting in early termination of the study. Decreases in peripheral blood VEGF-A levels and VEGF-C levels, and CD146 and CD34/133 counts relative to pretreatment were detected. Limited changes in antitumor T cell immunity were observed.

CONCLUSIONS

ABT-510 therapy administered at 100 mg twice/day in patients with MM did not demonstrate definite clinical efficacy. Further dose escalation or combination with cytotoxic therapy may be more effective therapeutically.

Elastin-elastases and inflamm-aging

Degradation of elastin, the main amorphous component of elastic fibers, by elastases belonging to the serine, metallo, or cysteine families leads to the generation of elastin fragments, designated as elastokines in keeping with their cytokine-like properties. Generation of elastokines from one of the longest lived protein in human might represent a strong tissue repair signal. Indeed, they (1) exhibit potent chemotactic activity for leukocytes, (2) stimulate fibroblast and smooth muscle cell proliferation, and (3) display proangiogenic activity as potent as VEGF. However, continuous exposure of cells to these matrikines, through increased elastase(s) expression with age, can contribute to the formation of a chronic inflammatory state, that is, inflamm-aging. Importantly, binding of elastokines to S-Gal, their cognate receptor, proved to stimulate matrix metalloproteinase expression in normal and cancer cells. Besides, these elastin fragments can polarize lymphocytes toward a Th-1 response or induce an osteogenic response in smooth muscle cells, and arterial wall calcification. In this chapter, emphasis will be made on the contribution of elastokines on the genesis of age-related arterial wall diseases, particularly abdominal aortic aneurysms (AAAs). An elastokine theory of AAAs progression will be proposed. Age is one main risk factor of cancer incidence and development. The myriad of biological effects exerted by elastokines on stromal and inflammatory cells led us to hypothesize that they might be main actors in elaborating a favorable cancerization field in melanoma; for instance these peptides could catalyze the vertical growth phase transition in melanoma through increased expression of gelatinase A and membrane-type 1 matrix metalloproteinase.

A possible additional diagnostic tool for cutaneous melanoma

The rise in incidence of malignant melanoma and the dismal prognosis of late detection emphasize the need for early detection and recognition of the disease. The well-known ABCD method for detection of melanoma has recently been revised by adding an "E" for changes in size, shape, color, crusting, itching, bleeding, and erythema. In an observational study, 8 of 14 (57%) melanoma patients exhibited a particular reddish hue to the skin adjacent to the melanoma, with no distinguishable borders. In another study, vascular endothelial growth factor was positive in biopsy specimens from 3 of 6 (50%) patients with erythema and in 4 of 7 (57%) patients without erythema. Platelet-derived growth factor was positive in all 6 (100%) of the patients with erythema and in 4 of the 7 (57%) without erythema. This erythema can help alert the clinician to the presence of malignant melanoma and serve as a prognostic factor or an indicator of the efficacy of treatment.

Molecular diagnostics in melanoma

Molecular pathology is rapidly evolving, featuring continuous technologic improvements that offer novel clinical opportunities for the recognition of disease predisposition, for identifying sub-clinical disease, for more accurate diagnosis, for selecting efficacious and non-toxic therapy, and for monitoring of disease outcome. Currently, the identification and prognosis of primary cutaneous melanoma is based on histologic factors (tumor depth and ulceration) and clinical factors (number of lymph node and/or distant metastases). However, metastasis can occur in patients with thin melanomas, and sentinel lymph node biopsy does not identify all patients at risk for distant metastasis. New markers exist that correlate with melanoma progression, which may aid in melanoma identification, prognostication, and detection of minimal residual disease/early recurrence. Moreover, not many therapeutic options exist for melanoma as no regimen prolongs survival. Emerging data with investigational therapies suggest that certain markers might play a crucial role in identifying patients who will respond to therapy or show utility in the monitoring the response to therapy. Herein, molecular diagnostics that can potentially benefit the individual melanoma patient will be discussed.

Increased laser Doppler flow in skin tumors corresponds to elevated vessel density and reactive hyperemia

BACKGROUND/PURPOSE

Tumor angiogenesis plays a key role in tumor growth and formation of metastasis. Quantitative analysis of tumor blood flow is a prerequisite for developing novel treatment strategies such as antiangiogenic and antivascular treatment options. Laser Doppler flow in malignant melanomas has been shown to be increased compared with normal skin and melanocytic nevi. This study investigated whether this phenomenon is originated by elevated blood vessel density or by reactive hyperemia.

METHODS

Laser Doppler flow was studied in 35 melanocytic nevi, 22 malignant melanomas and three basal cell carcinomas. After excision digital imaging analysis was performed in microtome sections (factor VIII-associated antigen and CD 31 labelled). The ratio of vessel area in histological sections from tumor tissue and in non-lesional skin was calculated and related to Doppler flow values.

RESULTS

Malignant melanomas demonstrated an enlargement of vessel cross-sectional area by factor 3.7+/-1.9 and of Doppler flow by factor 10.56+/-10.7, and melanocytic nevi accomplished increase of vessel cross-sectional area by factor 1.7+/-0.9 and of Doppler flow by factor 2.7+/-3.5.

CONCLUSION

The laser Doppler flow is influenced by the number and the velocity of erythrocytes in the tissue. The greater increase of laser Doppler flow than of vessel density in histological sections demonstrates that the flow signal in skin tumors is caused by neovascularization as well as by functional hyperemia. Laser Doppler perfusion imaging is a useful method for non-invasive, repeated and quantitative assessment of tumor vascular network and effects of antiangiogenic treatment directed vs. tumor vasculature in vivo, but it cannot distinguish between increased vessel density and reactive hyperemia.

Normal human fibroblasts enable melanoma cells to induce angiogenesis in type I collagen

BACKGROUND

We previously reported that fibroblasts induce human microvascular endothelial cells (HMVECs) to differentiate from monolayer to capillarylike morphology. We now test the hypothesis that fibroblasts modulate angiogenesis in melanoma cells.

METHODS

We tested 12 human melanoma lines (2 radial growth phase (RGP), 3 vertical growth phase (VGP), and 7 metastatic (MM)) for ability to induce HMVECs to invade/migrate into collagen and form capillarylike networks. HMVEC monolayers were overlaid with 3-dimensional collagen gels embedded with melanoma cells alone (M), fibroblasts alone (F), or a 1:1 mixture of the 2 cells (M+F). After 5 days, gels were removed, fixed, and HMVEC networks were quantified by von Willebrand's factor (vWF) immunofluorescence. The influence of soluble factors on HMVEC invasion/migration into collagen was assessed with the use of acellular 3-D collagen gels overlaid on HMVEC monolayers, cultured with conditioned media (CM) derived from monolayers of M, F, or M+F. Angiogenic growth factors involved in the observed invasion/migration were identified with the use of a RayBio Cytokine Antibody Array (RayBiotech, Norcross, Ga).

RESULTS

Cell line-specific variability in melanoma-supported angiogenesis was observed only when in combination with fibroblasts (analysis of variance [ANOVA], P < .01). Melanoma plus fibroblasts uniformly resulted in a significantly higher angiogenic response than melanoma alone (P < .05). One vertical growth phase and one metastatic melanoma line, while weakly angiogenic alone, induced significantly higher angiogenesis than either fibroblast or melanoma alone (P < .05) when combined with fibroblasts. CM from M or M+F induced significantly less HMVEC invasion/migration into collagen than CM from fibroblasts alone. Interleukin 8, monocyte chemotactic protein-1, and tissue inhibitor of metalloproteinase-2 were identified as significantly elevated in the media derived from M+F cultures, compared with either cell type alone.

CONCLUSION

To our knowledge, this is the first report demonstrating that melanoma-supported angiogenesis in collagen is more significantly influenced by normal skin-derived fibroblasts than by the intrinsic biology of the melanoma cell type. Interleukin 8, monocyte chemotactic protein-1, and tissue inhibitor of metalloproteinase-2 are implicated as potential paracrine factors regulating this observed effect.

Molecular MR imaging of melanoma angiogenesis with alphanubeta3-targeted paramagnetic nanoparticles

Neovascularization is a critical component in the progression of malignant melanoma. The objective of this study was to determine whether alpha(nu)beta(3)-targeted paramagnetic nanoparticles can detect and characterize sparse alpha(nu)beta integrin expression on neovasculature induced by nascent melanoma xenografts ( approximately 30 mm(3)) at 1.5T. Athymic nude mice bearing human melanoma tumors were intravenously injected with alpha(v)beta(3)-integrin-targeted paramagnetic nanoparticles, nontargeted paramagnetic nanoparticles, or alpha(v)beta(3)-targeted-nonparamagnetic nanoparticles 2 hr before they were injected with alpha(v)beta(3)-integrin-targeted paramagnetic nanoparticles (i.e., in vivo competitive blockade) and imaged with MRI. Contrast enhancement of neovascularity in animals that received alpha(nu)beta(3)-targeted paramagnetic nanoparticles increased 173% by 120 min. Signal contrast with nontargeted paramagnetic nanoparticles was approximately 50% less than that in the targeted group (P < 0.05). Molecular MRI results were corroborated by histology. In a competitive cell adhesion assay, incubation of alpha(nu)beta(3)-expressing cells with targeted nanoparticles significantly inhibited binding to a vitronectin-coated surface, confirming the bioactivity of the targeted nanoparticles. The present study lowers the limit previously reported for detecting sparse biomarkers with molecular MRI in vivo. This technique may be employed to noninvasively detect very small regions of angiogenesis associated with nascent melanoma tumors, and to phenotype and stage early melanoma in a clinical setting.