The role of mast cells in cutaneous melanoma remains unclear. Tryptase and chymase are serine proteinases and major proteins in mast cell secretory granules. Therefore, this study aimed to investigate the presence of tryptase and chymase mast cells in benign and malignant cutaneous melanocytic lesions and in lymph node metastases of melanomas. The presence of positively stained mast cells was correlated with clinicopathological characteristics in invasive melanomas. Paraffin-embedded sections of 28 benign (13 intradermal, 10 compound, and five junctional nevi) and 26 dysplastic nevi, 15 in-situ melanomas, 36 superficially (pT1, Breslow's thickness<1 mm), and 49 deeply (pT4, Breslow's thickness>4 mm) invasive melanomas and 30 lymph node metastases were immunohistochemically stained for mast cell tryptase and chymase, and immunopositive cells were counted using the hotspot counting method. The mean count of tryptase and chymase mast cells was lower in invasive melanomas compared with in-situ melanomas and dysplastic and benign nevi. In deeply invasive melanomas, the difference was statistically significant compared with dysplastic nevi (P=0.003 for tryptase and P=0.009 for chymase) and in-situ melanomas (0.043 for tryptase). Low numbers of tryptase mast cells were associated with poor overall survival (P=0.031) in deeply invasive melanomas and with a more advanced stage (T1b, P=0.008) in superficially invasive melanomas. Low numbers of chymase mast cells were associated with microsatellites (P=0.017) in deeply invasive melanomas. The results suggest that these serine proteinases of mast cells may be protective in the pathogenesis of melanoma.

BackgroundHyaluronan is a large extracellular matrix molecule involved in several biological processes such as proliferation, migration and invasion. In many cancers, hyaluronan synthesis is altered, which implicates disease progression and metastatic potential. We have previously shown that synthesis of hyaluronan and expression of its synthases 1–2 (HAS1-2) decrease in cutaneous melanoma, compared to benign melanocytic lesions.MethodsIn the present study, we compared immunohistological staining results of HAS1 and HAS2 with clinical and histopathological parameters to investigate whether HAS1 or HAS2 has prognostic value in cutaneous melanoma. The specimens consisted of 129 tissue samples including superficial (Breslow ≤ 1 mm) and deep (Breslow > 4 mm) melanomas and lymph node metastases. The differences in immunostainings were analysed with non-parametric Mann–Whitney U test. Associations between immunohistological staining results and clinical parameters were determined with the χ2 test. Survival between patient groups was compared by the Kaplan-Meier method using log rank test and Cox’s regression model was used for multivariate analyses.ResultsThe expression of HAS1 and HAS2 was decreased in deep melanomas and metastases compared to superficial melanomas. Decreased immunostaining of HAS2 in melanoma cells was significantly associated with several known unfavourable histopathologic prognostic markers like increased mitotic count, absence of tumor infiltrating lymphocytes and the nodular subtype. Furthermore, reduced HAS1 and HAS2 immunostaining in the melanoma cells was associated with increased recurrence of melanoma (p = 0.041 and p = 0.006, respectively) and shortened disease- specific survival (p = 0.013 and p = 0.001, respectively).ConclusionsThis study indicates that reduced expression of HAS1 and HAS2 is associated with melanoma progression and suggests that HAS1 and HAS2 have a prognostic significance in cutaneous melanoma.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-016-2344-8) contains supplementary material, which is available to authorized users.

Aberrant hyaluronan expression implicates aggressive disease progression and metastatic potential in many cancers. In tumors originating from simple epithelium, hyaluronan amount is increased both in the epithelial and stromal component and it correlates with patient's poor overall prognosis. The role of hyaluronan degrading enzymes (hyaluronidases, HYAL1-2) in cancer progression is controversial. Hyaluronidases are proposed to be both tumor suppressors and tumor promoters. In this retrospective study, we characterized the expression levels of HYAL1 and HYAL2 and correlated their expression to hyaluronan in the different stages of primary skin melanoma as well as in metastatic melanoma. Superfically (pT1) and deeply (pT4) invasive melanoma (Breslow &lt; 1mm (n=18) and Breslow &gt; 4mm (n=18)), in situ melanoma (n=17), lymph node metastasis (n=19), dysplastic nevi (n=28) and benign nevi samples (n=29) were analyzed for hyaluronan staining and HYAL1 and HYAL2 immunoreactivity (ABCAM antibodies) in paraffin tissue sections. Stainings were evaluated for their intensity and coverage. The tissue area for hyaluronan and HYAL1/HYAL2 positive staining was estimated with a five-level scoring from 0-4 and the staining intensity of melanocytic cells was evaluated with a four-level scoring (0-3; no color, weak, moderate and strong) by two independent observers. Compared to benign nevi and in situ melanoma, the cell-associated hyaluronan staining coverage and intensity were clearly reduced in the invasive part of melanoma with advanced Breslow depth. Strong hyaluronan staining intensity was detected in 36% of in situ melanoma cases and in 21% of superficial melanoma (Breslow &lt; 1mm) cases, while in the deeply invasive melanoma group (Breslow &gt; 4mm), only 6% of cases showed strong hyaluronan staining intensity. In addition, in lymph node metastases the melanoma cells showed low hyaluronan staining intensity or were totally hyaluronan negative. However, the tumor stroma was highly hyaluronan positive in all groups. HYAL1 immunoreactivity was found in melanocytic cells both in benign nevi and melanoma samples while the tumor stromal cells were negative. The coverage of HYAL2 immunoreactivity was parallel to HYAL1, although its staining intensity was lower than that of HYAL1. Our results suggest that hyaluronan content is clearly decreased in invasive primary and metastatic melanoma compared to benign nevi. The results from hyaluronan stainings will be compared with clinical follow-up data to study the prognostic value of hyaluronan in melanoma. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2458. doi:1538-7445.AM2012-2458

Diffusely infiltrating astrocytomas are central nervous system tumors originating from astrocytic glial cells or their precursor cells. In this retrospective study we investigated the content of hyaluronan and the expression of hyaluronan metabolizing enzymes and its cell surface receptor, CD44, in these aggressive tumors. Hyaluronan is a large extracellular matrix molecule synthesized by three hyaluronan synthases (HAS1-3) on the plasma membrane and degraded by two hyaluronidases (HYAL1-2). In many tumors, aberrant hyaluronan metabolism implicates aggressive disease progression and metastatic potential. Our material consisted of 165 diffusely infiltrating astrocytomas (WHO grades II-IV). Tumor samples were processed into tissue microarray (TMA) blocks. The TMA sections were stained for hyaluronan, CD44, HAS1, HAS2, HAS3 and HYAL2. The staining intensity of astrocytomas was evaluated with a four-level scoring (0-3; no color, weak, moderate and strong) by two independent observers. The immunostaining results were compared with χ2 -test or with Kruskal-Wallis test for correlation with clinicopathological parameters and survival analyses were done with Kaplan-Meier log rank test and Cox regression. Hyaluronan and CD44 were strongly expressed in astrocytic gliomas but their expression did not correlate with WHO grade, cell proliferation activity by Ki-67, p53 status, epidermal growth factor receptor (EGFR) amplification or IDH1 mutation. Whereas HAS2 staining intensity showed a significant correlation with IDH1 mutation. Tumors with high HAS2 expression were IDH1 negative (p = 0.003). In addition, in non-parametric tests increased HAS2 staining intensity showed association with increased cell proliferation (p = 0.013) and in log rank test with decreased overall survival of patients (p = 0.001). Variables included in the multivariable Cox regression analysis were HAS2 staining intensity, p53 status, EGFR amplification, IDH1 mutation and WHO tumor grade; in this analysis HAS2 expression turned out to be a significant independent prognostic factor (p = 0.008). This study indicates that elevated expression of HAS2 is associated with glioma progression and suggests that HAS2 has a prognostic significance in diffusely infiltrating astrocytomas. Citation Format: Mari J. Poukka, Hannu Haapasalo, Kirsi J. Rilla, Kristiina Tyynelä-Korhonen, Ylermi Soini, Sanna M. Pasonen-Seppänen. Elevated expression of hyaluronan synthase 2 associates with poor prognosis in diffusely infiltrating astrocytomas. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3111.