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

The retinal pigmentation pathway in human albinism: Not so black and white

Albinism is a pigment disorder affecting eye, skin and/or hair. Patients usually have decreased melanin in affected tissues and suffer from severe visual abnormalities, including foveal hypoplasia and chiasmal misrouting. Combining our data with those of the literature, we propose a single functional genetic retinal signalling pathway that includes all 22 currently known human albinism disease genes. We hypothesise that defects affecting the genesis or function of different intra-cellular organelles, including melanosomes, cause syndromic forms of albinism (Hermansky-Pudlak (HPS) and Chediak-Higashi syndrome (CHS)). We put forward that specific melanosome impairments cause different forms of oculocutaneous albinism (OCA1-8). Further, we incorporate GPR143 that has been implicated in ocular albinism (OA1), characterised by a phenotype limited to the eye. Finally, we include the SLC38A8-associated disorder FHONDA that causes an even more restricted "albinism-related" ocular phenotype with foveal hypoplasia and chiasmal misrouting but without pigmentation defects. We propose the following retinal pigmentation pathway, with increasingly specific genetic and cellular defects causing an increasingly specific ocular phenotype: (HPS1-11/CHS: syndromic forms of albinism)-(OCA1-8: OCA)-(GPR143: OA1)-(SLC38A8: FHONDA). Beyond disease genes involvement, we also evaluate a range of (candidate) regulatory and signalling mechanisms affecting the activity of the pathway in retinal development, retinal pigmentation and albinism. We further suggest that the proposed pigmentation pathway is also involved in other retinal disorders, such as age-related macular degeneration. The hypotheses put forward in this report provide a framework for further systematic studies in albinism and melanin pigmentation disorders.

Correlation Between KIT Expression and c-Kit Mutations in 2 Subtypes of Canine Oral Melanocytic Neoplasms

c-Kit mutations have been reported in 15% to 40% of certain human melanoma subtypes, including those histologically similar to canine oral malignant melanomas. Therapeutic response to tyrosine kinase inhibitors has been demonstrated in those human patients. As canine oral malignant melanomas tend to have a poor prognosis despite aggressive surgical removal, evaluation of KIT expression and identification of c-Kit mutations in canine oral melanocytic neoplasms was performed to determine if there is any indication that tyrosine kinase inhibitor drugs might effectively treat any of these cases. This study evaluated 27 canine oral malignant melanomas and 12 canine histologically well-differentiated oral melanocytic neoplasms for activating c-Kit mutations, determined differences in immunohistochemical expression of KIT and c-Kit mutation status, and determined if KIT expression could predict c-Kit mutation status. Among samples that contained intraepithelial nests of neoplastic melanocytes in the KIT-labeled sections, KIT was expressed within cells in these nests in 22/23 (96%) malignant melanomas and 5/7 histologically well-differentiated neoplasms. KIT was expressed in 10% to 30% of neoplastic melanocytes in the lamina propria in 3/24 (13%) malignant melanomas, but 0/9 (0%) histologically well-differentiated neoplasms. Next-generation sequencing identified 85 variants in c-Kit, including 9 nonsynonymous mutations that resulted in amino acid changes predicted to affect protein function. c-Kit mutations with predicted deleterious protein effects were more common in malignant melanomas (8/27 [30%] vs 1/12 [8%]). There was no apparent relationship between detected c-Kit mutations and KIT expression. These results do not support the use of therapies that target c-Kit.

Blood and urine concentrations of vascular endothelial growth factor in dogs with tumours

Vascular endothelial growth factor (VEGF) is a potent mitogen for vascular endothelial cells. It improves cell survival, stimulates angiogenesis, inhibits cell apoptosis and strongly enhances vascular permeability. In this study, VEGF concentrations were assayed in blood plasma and urine of 22 dogs with neoplasms (lymphosarcoma, splenic haemangiosarcoma and mammary gland carcinoma) and in 7 healthy dogs by means of ELISA. Average blood plasma VEGF in control dogs was 42.13 ± 7.37 pg/mL, while in dogs with lymphoma – 113.35 ± 16.48 pg/mL, in dogs with haemangiosarcoma – 154.85 ± 48.46 pg/mL and in dogs with mammary gland carcinoma – 104.31 ± 12.45 pg/mL. Urine VEGF concentrations in dogs affected with lymphosarcoma were 712.42 ± 233.85 ng/g uCr, in animals with haemangiosarcoma – 223.50 ± 262.33 ng/g uCr and in those with mammary carcinoma: 1053.92 ± 311.63 ng/g uCr. In healthy controls average urine VEGF was 310.11 ± 28.11 ng/g uCr.

Targeting SRPK1 to control VEGF-mediated tumour angiogenesis in metastatic melanoma

Background:

Current therapies for metastatic melanoma are targeted either at cancer mutations driving growth (e.g., vemurafenib) or immune-based therapies (e.g., ipilimumab). Tumour progression also requires angiogenesis, which is regulated by VEGF-A, itself alternatively spliced to form two families of isoforms, pro- and anti-angiogenic. Metastatic melanoma is associated with a splicing switch to pro-angiogenic VEGF-A, previously shown to be regulated by SRSF1 phosphorylation by SRPK1. Here, we show a novel approach to preventing angiogenesis—targeting splicing factor kinases that are highly expressed in melanomas.

Methods:

We used RT–PCR, western blotting and immunohistochemistry to investigate SRPK1, SRSF1 and VEGF expression in tumour cells, and in vivo xenograft assays to investigate SRPK1 knockdown and inhibition in vivo.

Results:

In both uveal and cutaneous melanoma cell lines, SRPK1 was highly expressed, and inhibition of SRPK1 by knockdown or with pharmacological inhibitors reduced pro-angiogenic VEGF expression maintaining the production of anti-angiogenic VEGF isoforms. Both pharmacological SRPK1 inhibitors and SRPK1 knockdown reduced growth of human melanomas in vivo, but neither affected cell proliferation in vitro.

Conclusions:

These results suggest that selective blocking of pro-angiogenic isoforms by inhibiting splice-site selection with SRPK1 inhibitors reduces melanoma growth. SRPK1 inhibitors may be used as therapeutic agents.

Randomized, double-blind, placebo-controlled trial of sulindac in individuals at risk for melanoma: evaluation of potential chemopreventive activity

BACKGROUND

Reduced melanoma risk has been reported with regular use of nonsteroidal anti-inflammatory drugs (NSAIDs). However, the ability of NSAIDs to reach melanocytes in vivo and modulate key biomarkers in preneoplastic lesions such as atypical nevi has not been evaluated.

METHODS

This randomized, double-blind, placebo-controlled trial of sulindac was conducted in individuals with atypical nevi (AN) to determine bioavailability of sulindac and metabolites in nevi and effect on apoptosis and vascular endothelial growth factor A (VEGFA) expression in AN. Fifty subjects with AN ≥ 4 mm in size and 1 benign nevus (BN) were randomized to sulindac (150 mg twice a day) or placebo for 8 weeks. Two AN were randomized for baseline excision, and 2 AN and BN were excised after intervention.

RESULTS

Postintervention sulindac, sulindac sulfone, and sulindac sulfide concentrations were 0.31 ± 0.36, 1.56 ± 1.35, and 2.25 ± 2.24 μg/mL in plasma, and 0.51 ± 1.05, 1.38 ± 2.86, and 0.12 ± 0.12 μg/g in BN, respectively. Sulindac intervention did not significantly change VEGFA expression but did increase expression of the apoptotic marker cleaved caspase-3 in AN (increase of 3 ± 33 in sulindac vs decrease of 25 ± 45 in the placebo arm, P = .0056), although significance was attenuated (P = .1103) after adjusting for baseline expression.

CONCLUSIONS

Eight weeks of sulindac intervention resulted in high concentrations of sulindac sulfone, a proapoptotic metabolite, in BN but did not effectively modulate VEGFA and cleaved caspase-3 expression. Study limitations included limited exposure time to sulindac and the need to optimize a panel of biomarkers for NSAID intervention studies.

Immunohistochemical expression of VEGF, HIF1-a, and PlGF in malignant melanomas and dysplastic nevi

We evaluated the role of vascular endothelial growth factor (VEGF), placental growth factor (PlGF), and hypoxia-inducible factor 1-a (HIF1-a) in melanoma angiogenesis and investigated their expression in dysplastic nevi, as potential melanoma precursors. In addition, we examined a possible correlation of VEGF expression with PlGF and HIF1-a. These factors were detected immunohistochemically in 95 melanomas of all types and stages and in 28 dysplastic nevi. We used 10 intradermal melanocytic nevi as controls. HIF1-a was expressed in 93 out of 95 (97.89%) melanomas and in none of the dysplastic or control nevi. HIF1-a expression was more intense in melanocytes around necrotic areas but did not correlate with melanoma type, the Clark staging or the Breslow thickness. A strong positive association was detected between HIF1-a and VEGF expression in all cases. VEGF was detected in 82 out of 95 (86.31%) melanomas and in 21 out of 28 (75%) dysplastic nevi, whereas it was expressed weakly in neoplastic cells of the controls. Its expression was more intense in melanomas, especially in nodular melanomas of elevated stage and thickness. PIGF was detected in 46 out of 95 (48.42%) melanomas and in none of the nevi. Expression did not correlate with melanoma staging nor thickness; however, it was more intense in superficial spreading melanomas, where a weak positive association between VEGF and PlGF was also detected. There was no association between HIF1-a and PlGF in any melanoma type. Hypoxia, through the expression of HIF1-a, plays a key role in melanoma progression; it activates VEGF secretion, which induces angiogenesis and metastasis. The role of PlGF seems to be limited.

The usefulness of c-Kit in the immunohistochemical assessment of melanocytic lesions

C-Kit (CD117), the receptor for the stem cell factor, a growth factor for melanocyte migration and proliferation, has shown differential immunostaining in various benign and malignant melanocytic lesions. The purpose of this study is to compare c-Kit immunostaining in benign nevi and in primary and metastatic malignant melanomas, to determine whether c-Kit can aid in the differential diagnosis of these lesions. c-Kit immunostaining was performed in 60 cases of pigmented lesions, including 39 benign nevi (5 blue nevi, 5 intradermal nevi, 3 junctional nevi, 15 cases of primary compound nevus, 11 cases of Spitz nevus), 18 cases of primary malignant melanoma and 3 cases of metastatic melanoma. The vast majority of nevi and melanomas examined in this study were positive for c-Kit, with minimal differences between benign and malignant lesions. C-Kit cytoplasmatic immunoreactivity in the intraepidermal proliferating nevus cells, was detected in benign pigmented lesions as well as in malignant melanoma, increasing with the age of patients (P=0.007) in both groups. The patient's age at presentation appeared to be the variable able to cluster benign and malignant pigmented lesions. The percentage of c-Kit positive intraepidermal nevus cells was better associated with age despite other variables (P=0.014). The intensity and percentage of c-Kit positivity in the proliferating nevus cells in the dermis was significantly increased in malignant melanocytic lesions (P=0.015 and P=0.008) compared to benign lesions (compound melanocytic nevi, Spitz nevi, intradermal nevi, blue nevi). Immunostaning for c-Kit in metastatic melanomas was negative. Interestingly in two cases of melanoma occurring on a pre-existent nevus, the melanoma tumor cells showed strong cytoplasmatic and membranous positivity for c-kit, in contrast with the absence of any immunoreactivity in pre-existent intradermal nevus cells. C-Kit does not appear to be a strong immunohistochemical marker for distinguishing melanoma from melanocytic nevi, if we consider c-Kit expression in intraepidermal proliferating cells. The c-Kit expression in proliferating melanocytes in the dermis could help in the differential diagnosis between a superficial spreading melanoma (with dermis invasion) and a compound nevus or an intradermal nevus. Finally, c-Kit could be a good diagnostic tool for distinguishing benign compound nevi from malignant melanocytic lesions with dermis invasion and to differentiate metastatic melanoma from primary melanoma.

Expression of c-Kit, p-ERK and cyclin D1 in malignant melanoma: an immunohistochemical study and analysis of prognostic value

BACKGROUND

The mitogen-activated protein kinase (MAPK) signaling pathway is one of the major cascades that are crucial for the initiation and progression of melanoma; however, the influence of these signaling molecules on patient survival has not been clarified.

OBJECTIVE

The purpose of this study was to analyze the protein expression of MAPK signaling molecules in melanoma, and to correlate the expression status with clinicopathologic parameters.

METHODS

Expression of c-Kit, phosphorylated ERK (p-ERK), and cyclin D1 was examined by immunohistochemistry in 78 primary melanomas, 24 metastatic lesions, and in 42 benign nevi. The following clinicopathologic variables were evaluated: age, gender, histologic type, tumor site, Breslow thickness, Clark's level, ulceration, and survival period. Statistical analyses were performed for assessment of associations and melanoma-specific survival.

RESULTS

The expression of c-Kit, p-ERK, and cyclin D1 was significantly higher in primary melanomas than in nevi. c-Kit immunoreactivity was highest in thin (Tis-pT2) melanomas, and showed a significant reduction with tumor progression and metastasis. The expression of p-ERK was high in all stages of melanoma. Cyclin D1 positivity increased significantly according to tumor progression, but decreased in metastases. A significant correlation between p-ERK and cyclin D1 expression was observed. Survival analysis failed to detect any trends towards shorter or longer survival among patients expressing either c-Kit, p-ERK or cyclin D1.

CONCLUSIONS

The expression of c-Kit, p-ERK, and cyclin D1 might help to differentiate thin melanoma from melanocytic nevus, but it appears to lack prognostic potential.

Expression of vascular endothelial growth factor in melanocytic nevi

Melanocytic nevi represent a benign neoplastic proliferation of melanocytes. The level of vascular endothelial growth factor expression in these proliferations is low in most cases; whereas an increased expression of this factor may be an indicator of pre-neoplastic changes in melanocyte lesions. We performed a semi-quantitative assessment of the level of vascular endothelial growth factor expression (score 0 to 3) on samples taken from 34 patients with benign melanocyte alterations of the skin. Melanocytic nevi showed an expression of vascular endothelial growth factor in 79.41% of the cases. The low level of expression (score 1) was seen in 70.59% cases. The results showed no statistically significant difference in the presence and level of vascular endothelial growth factor expression in relation to the following morphological parameters: histological type, a defect in the surface, density of inflammation infiltrate, mitotic index, growth phase and cell type.

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.

Significance of vascular endothelial growth factor expression in skin melanoma

Background/Aim. Melanoma is a heterogeneous disease of skin and mucous membranes which shows significant increase in incidence worldwide in the past decades. In the process of forming new blood vessels stimulators of angiogenesis participate. There is an increase production of vascular endothelial growth factor (VEGF-C and VEGF-D), which expression cause change of endothelial cells, and higher degree of tumor's aggressiveness. The aim of this research was to determine the level of VEGF expression in skin melanoma in different body regions and in different primary stages of the disease. Methods. The research was conducted on bioptic materials of skin in 39 patients. On excision-made materials a routine histological preparation was done and following parameters were determined: histological type, alteration thickness (according to Breslow), Clark level, TNM (Tumor Nodus Metastasis) stage (pT), alteration width, thickness of lymphocytic infiltration in the tumor, mitotic index, phase of the tumor growth, presence of ulcerations, cellular type of the tumor, localization and level of VEGF expression. Results. Analysis confirmed that 61.54% of skin melanoma showed a high VEGF expression. Nodular and acral lentiginous melanomas showed more frequently a high level of VEGF expression, while superficial spreading melanoma showed a lower level of VEGF expression (p = 0.032, p < 0.05). A higher level of expression was present in thicker melanomas (higher in the Breslow stage; p = 0.011, p < 0.05). The width of the lesion did not have an influence on the level of VEGF expression in melanoma (U =142.000, p = 0.273). Conclusion. Melanomas show a higher level of VEGF expression. Nodular and acral lentiginous types of melanoma show a high level of VEGF expression, while superficial spreading melanoma shows a lower level of VEGF expression. Melanomas in higher-stage disease (Breslow, Clark, pTNM) show a higher level of VEGF expression.

Tissue biomarkers for prognosis in cutaneous melanoma: a systematic review and meta-analysis

In the clinical management of early-stage cutaneous melanoma, it is critical to determine which patients are cured by surgery alone and which should be treated with adjuvant therapy. To assist in this decision, many groups have made an effort to use molecular information. However, although there are hundreds of studies that have sought to assess the potential prognostic value of molecular markers in predicting the course of cutaneous melanoma, at this time, no molecular method to improve risk stratification is part of recommended clinical practice. To help understand this disconnect, we conducted a systematic review and meta-analysis of the published literature that reported immunohistochemistry-based protein biomarkers of melanoma outcome. Three parallel search strategies were applied to the PubMed database through January 15, 2008, to identify cohort studies that reported associations between immunohistochemical expression and survival outcomes in melanoma that conformed to the REMARK criteria. Of the 102 cohort studies, we identified only 37 manuscripts, collectively describing 87 assays on 62 distinct proteins, which met all inclusion criteria. Promising markers that emerged included melanoma cell adhesion molecule (MCAM)/MUC18 (all-cause mortality [ACM] hazard ratio [HR] = 16.34; 95% confidence interval [CI] = 3.80 to 70.28), matrix metalloproteinase-2 (melanoma-specific mortality [MSM] HR = 2.6; 95% CI = 1.32 to 5.07), Ki-67 (combined ACM HR = 2.66; 95% CI = 1.41 to 5.01), proliferating cell nuclear antigen (ACM HR = 2.27; 95% CI = 1.56 to 3.31), and p16/INK4A (ACM HR = 0.29; 95% CI = 0.10 to 0.83, MSM HR = 0.4; 95% CI = 0.24 to 0.67). We further noted incomplete adherence to the REMARK guidelines: 14 of 27 cohort studies that failed to adequately report their methods and nine studies that failed to either perform multivariable analyses or report their risk estimates were published since 2005.

Human melanoma cytolysis by combined inhibition of mammalian target of rapamycin and vascular endothelial growth factor/vascular endothelial growth factor receptor-2

Vascular endothelial growth factor (VEGF) plays a vital role in tumor angiogenesis. VEGF is produced by human melanomas, and the VEGF receptor 2 (VEGFR-2) is expressed by most advanced stage melanomas, suggesting the possibility of an autocrine loop. Here, we show that bevacizumab, an anti-VEGF antibody, inhibits proliferation of VEGFR-2(+) melanoma cell lines by an average of 41%; however, it failed to inhibit proliferation of VEGFR-2(neg) melanoma cell lines. The growth inhibitory effect of bevacizumab was eliminated by VEGFR-2 knockdown with small interfering RNA, showing that VEGF autocrine growth in melanoma is mediated through VEGFR-2. However, bevacizumab inhibition of autocrine signals did not completely inhibit cell proliferation nor cause cell death. Cell survival is mediated partially through mammalian target of rapamycin (mTOR), which is inhibited by rapamycin. Combination of bevacizumab with rapamycin caused loss of half of the VEGFR-2(+) melanoma cells, but no reduction in the number of VEGFR-2(neg) melanoma cells. The results show (a) an autocrine growth loop active in VEGFR-2(+) melanoma, (b) a nonangiogenic mechanism for inhibition of melanoma by blocking autocrine VEGFR-2 activation, and (c) a possible therapeutic role for combination of inhibitors of mTOR plus VEGF in selected melanomas.

Expression of VEGF(xxx)b, the inhibitory isoforms of VEGF, in malignant melanoma

Malignant melanoma is the most lethal of the skin cancers and the UK incidence is rising faster than that of any other cancer. Angiogenesis – the growth of new vessels from preexisting vasculature – is an absolute requirement for tumour survival and progression beyond a few hundred microns in diameter. We previously described a class of anti-angiogenic isoforms of VEGF, VEGF_xxxb, that inhibit tumour growth in animal models, and are downregulated in some cancers, but have not been investigated in melanoma. To determine whether VEGF_xxxb expression was altered in melanoma, PCR and immunohistochemistry of archived human tumour samples were used. In normal epidermis and in a proportion of melanoma samples, VEGF_xxxb staining was seen. Some melanomas had much weaker staining. Subsequent examination revealed that expression was significantly reduced in primary melanoma samples (both horizontal and vertical growth phases) from patients who subsequently developed tumour metastasis compared with those who did not (analysis of variance (ANOVA) P<0.001 metastatic vs nonmetastatic), irrespective of tumour thickness, while the surrounding epidermis showed no difference in expression. Staining for total VEGF expression showed staining in metastatic and nonmetastatic melanomas, and normal epidermis. An absence of VEGF_xxxb expression appears to predict metastatic spread in patients with primary melanoma. These results suggest that there is a switch in splicing as part of the metastatic process, from anti-angiogenic to pro-angiogenic VEGF isoforms. This may form part of a wider metastatic splicing phenotype.

Circulating serum levels of angiogenic factors and vascular endothelial growth factor receptors 1 and 2 in melanoma patients

Angiogenesis is essential for tumor progression and metastasis; however, the angiogenesis regulators that are biologically relevant for melanoma are still unknown. In this study, we analyzed the circulating serum levels of potent angiogenic factors, including vascular endothelial growth factor (VEGF), angiogenin, transforming growth factor-beta1 and VEGF receptors, VEGFR1 and VEGFR2, in human melanoma patients. One hundred and fourteen patients with histopathologically verified cutaneous melanoma at different stages and 30 healthy controls were investigated. Serum levels of angiogenic factors and VEGF receptors were quantitatively analyzed by solid-phase enzyme-linked immunosorbent assay. The age of the patients (61 men and 53 women) ranged from 18 to 80 years; median age was 51 years. Serum transforming growth factor-beta1 (P < 0.001), VEGF (P = 0.006) and VEGFR1 (P = 0.007) levels were significantly higher in patients with melanoma than in the control group. No significant differences, however, exist in the serum angiogenin and VEGFR2 levels between melanoma patients and the controls. The positive correlations of elevated serum levels of transforming growth factor-beta1, VEGF and VEGFR1 with advanced stages of disease were found. Significant relationship was found only between serum levels of VEGF and VEGFR2. Elevated serum transforming growth factor-beta1 (P < 0.001) and VEGF levels (P = 0.0012) were found to be poor prognostic factors. Serum level of angiogenin and VEGF receptors, however, had no effect on survival. Our data suggest that the angiogenic serum factors, including VEGF, transforming growth factor-beta1 and VEGFR1, but not angiogenin and VEGFR2 were increased in melanoma patients, especially associated with advanced disease stages. The mechanism of VEGF regulation of angiogenesis may in part be due to enhanced proliferation of VEGFRs, especially VEGFR1.

Interstitial cells of Cajal in health and disease. Part II: ICC and gastrointestinal stromal tumours

Mesenchymal tumours in the gastrointestinal tract have long been problematic in terms of diagnosis, prognosis and therapy, but recent advances in immunohistochemistry and related therapies have allowed more specific diagnosis. In particular, the recognition that both the interstitial cells of Cajal (ICC) and many gastrointestinal stromal tumours (GISTs) are positive for c-kit and CD34 and have other features similar to those of ICC has led to the use of imatinib, a novel small molecule therapy that blocks the CD117/c-kit tyrosine kinase receptor, which shows remarkable efficacy in treatment of malignant and metastatic GISTs as well as other malignancies.

Gastrointestinal stromal tumors: a contemporary review

The literature on gastrointestinal stromal tumors (GISTs) has rapidly expanded and has demonstrated how scientific advancements in diagnosis can revolutionize the understanding of disease, while paving the way for effective treatment. While KIT (CD117) immunohistochemistry has established our definition of GISTs, molecular genetics continue to refine it. Elucidation of the aberrant receptor tyrosine kinase (RTK) model of GIST pathogenesis through mutations in c-kit and platelet-derived growth factor alpha PDGFRalpha proto-oncogenes has been prerequisite to the use of imatinib mesylate (STI571, Gleevec; Novartis, Switzerland), a molecular inhibitor of several tyrosine kinases, in the treatment of GISTs. In addition to providing a means for effective treatment, clarification of the molecular pathology of GISTs may potentially offer a new classification of these tumors by correlating genotype with histological, immunohistochemical, and clinical phenotype. This article seeks to review current knowledge of GISTs, offering a practical guide to their diagnosis and describing current epidemiological, molecular biological, and therapeutic aspects.

Expression of c-kit (CD117) in Spitz nevus and malignant melanoma

BACKGROUND

CD117, the receptor for kit-ligand, which is a growth factor for melanocyte migration and proliferation, has shown differential staining in various benign and malignant melanocytic lesions. The purpose of this study is to compare CD117 immunohistological staining in Spitz nevus versus malignant melanoma, to determine whether CD117 can aid in the diagnosis of these two lesions.

METHODS

CD-117 immunohistological staining was performed in 22 clinically and pathologically diagnosed pigmented lesions including 9 cases of Spitz nevus, 10 cases of primary MM and 3 cases of metastatic melanoma.

RESULTS

There was no significant difference in CD117 staining in either epidermis or dermis between Spitz nevi and primary melanomas. However staining of metastatic melanomas is less than dermal staining of primary MM and Spitz nevus.

CONCLUSIONS

CD117 is unlikely a useful diagnostic tool in differentiating Spitz nevus from primary MM. On the other hand, CD 117 may be useful in differentiating metastatic melanoma from primary melanoma in patients who had a history of melanoma and who present with new dermal lesions.

The role of c-kit and imatinib mesylate in uveal melanoma

Background

Uveal melanoma (UM) is the most common primary intraocular tumor in adults, leading to metastasis in 40% of the cases and ultimately to death in 10 years, despite local and/or systemic treatment. The c-kit protein (CD117) is a membrane-bound tyrosine kinase receptor and its overexpression has been observed in several neoplasms. Imatinib mesylate is a FDA approved compound that inhibits tyrosine quinase receptors, as well as c-kit. Imatinib mesylate controls tumor growth in up to 85% of advanced gastrointestinal stromal tumors, a neoplasia resistant to conventional therapy.

Methods

Fifty-five specimens of primary UM selected from the archives of the Ocular Pathology Laboratory, McGill University, Montreal, Canada, were immunostained for c-kit. All cells displaying distinct immunoreactivity were considered positive. Four human UM cell lines and 1 human uveal transformed melanocyte cell line were tested for in vitro proliferation Assays (TOX-6) and invasion assay with imatinib mesylate (concentration of 10 μM).

Results

The c-kit expression was positive in 78.2% of the UM. There was a statistical significant decrease in the proliferation and invasion rates of all 5 cell lines.

Conclusion

The majority of UM expressed c-kit, and imatinib mesylate does decrease the proliferation and invasion rates of human UM cell lines. These results justify the need for a clinical trial to investigate in vivo the response of UM to imatinib mesylate.