Cell proliferation in cutaneous malignant melanoma: relationship with neoplastic progression

Pitfalls in Cutaneous Melanoma Diagnosis and the Need for New Reliable Markers

Cutaneous melanoma is one of the most aggressive forms of skin cancer, with the development of advanced stage disease resulting in a high rate of patient mortality. Accurate diagnosis of melanoma at an early stage is essential to improve patient outcomes, as this enables treatment before the cancer has metastasised. Histopathologic analysis is the current gold standard for melanoma diagnosis, but this can be subjective due to discordance in interpreting the morphological heterogeneity in melanoma and other skin lesions. Immunohistochemistry (IHC) is sometimes employed as an adjunct to conventional histology, but it remains occasionally difficult to distinguish some benign melanocytic lesions and melanoma. Importantly, the complex morphology and lack of specific biomarkers that identify key elements of melanoma pathogenesis can make an accurate confirmation of diagnosis challenging. We review the diagnostic constraints of melanoma heterogeneity and discuss issues with interpreting routine histology and problems with current melanoma markers. Innovative approaches are required to find effective biomarkers to enhance patient management.

Characteristic of Ultrastructure of Mice B16 Melanoma Cells under the Influence of Different Lighting Regimes

Circadian rhythms of physiological processes, constantly being in a state of dynamic equilibrium and plastically associated with changes in environmental conditions, are the basis of homeostasis of an organism of human and other mammals. Violation of circadian rhythms due to significant disturbances in parameters of main environmental effectors (desynchronosis) leads to the development of pathological conditions and a more severe course of preexisting pathologies. We conducted the study of the ultrastructure of cells of mice transplantable malignant melanoma B16 under the condition of normal (fixed) lighting regime and under the influence of constant lighting. Results of the study show that melanoma B16 under fixed light regime represents a characteristic picture of this tumor-predominantly intact tissue with safe junctions of large, functionally active cells with highly irregular nuclei, developed organelles and a relatively low content of melanin. The picture of the B16 melanoma tissue structure and the ultrastructure of its cells under the action of constant lighting stand in marked contrast to the group with fixed light: under these conditions the tumor exhibits accelerated growth, a significant number of cells in the state of apoptosis and necrosis, ultrastructural signs of degradation of the structure and functions, and signs of embryonization of cells with the background of adaptation to oxygen deficiency.

3D models of the dynamics of cancer cells under external pressure

Skin cancer is one of the most frequent cancers worldwide. Recently, it has been shown that the tumor proliferation rate in skin and its dynamics can be changed by an osmotic pressure. However, these findings are rather unstructured. A weak pressure can slow down the tumor growth, while a very high pressure can, on the contrary, lead to accelerated growth and metastases. The magnitude and spatial distribution of osmotic pressures in tumors at present cannot be measured experimentally. Therefore, it is of particular interest to find appropriate models that would simulate the effects of additional osmotic pressures in skin and assess the features of its implementation. In this paper, we suggest an improved model based on the principles of the conventional hydrodynamic model for macrophase separations, which allows one to include not only the properties of healthy and cancer cells but also the microenvironment. We study and analyze the proliferation of cancer cells in 3D models of the epidermal layer of skin under an osmotic pressure. There are two suggested 3D models that are based on the same principles: (1) cellular cubic lattice and (2) cell spheroid. This allows expanding the application of the model depending on a given task. Here, we are focused on the study of melanoma at an early stage when there are not many cancer cells. Additional compressive and expansive pressures are added to the central part of the system. Both systems demonstrate similar results in slowing down the rate of tumor growth with a small pressure.

DNA Damage Repair Gene Set as a Potential Biomarker for Stratifying Patients with High Tumor Mutational Burden

Simple Summary

Immunotherapy has been a promising therapeutic approach for cancer treatment in recent years. Although cancer immunotherapy has achieved remarkable success, treatment response is only observed in a small number of patients. As nonresponders need to endure high treatment costs and toxicities with little benefit from treatment, identifying potential predictive biomarkers is critical to optimize the benefits of immunotherapy in patients. The total number of mutations in the tumor genome is a useful biomarker. Patients with a large number of mutations tend to respond better to cancer immunotherapy. However, assessment of the total number of mutations may not be easy. In this study, we identified gene sets with only a small number of genes whose mutations serve as an indicator of the total number of mutations. These cancer-specific gene sets can be used as a cost-effective approach to stratify patients with a large number of mutations in clinical practice.

Abstract

Tumor mutational burden (TMB) is a promising predictive biomarker for cancer immunotherapy. Patients with a high TMB have better responses to immune checkpoint inhibitors. Currently, the gold standard for determining TMB is whole-exome sequencing (WES). However, high cost, long turnaround time, infrastructure requirements, and bioinformatics demands have prevented WES from being implemented in routine clinical practice. Panel-sequencing-based estimates of TMB have gradually replaced WES TMB; however, panel design biases could lead to overestimation of TMB. To stratify TMB-high patients better without sequencing all genes and avoid overestimating TMB, we focused on DNA damage repair (DDR) genes, in which dysfunction may increase somatic mutation rates. We extensively explored the association between the mutation status of DDR genes and TMB in different cancer types. By analyzing the mutation data from The Cancer Genome Atlas, which includes information for 33 different cancer types, we observed no single DDR gene/pathway in which mutation status was significantly associated with high TMB across all 33 cancer types. Therefore, a computational algorithm was proposed to identify a cancer-specific gene set as a surrogate for stratifying patients with high TMB in each cancer. We applied our algorithm to skin cutaneous melanoma and lung adenocarcinoma, demonstrating that the mutation status of the identified cancer-specific DDR gene sets, which included only 9 and 14 genes, respectively, was significantly associated with TMB. The cancer-specific DDR gene set can be used as a cost-effective approach to stratify patients with high TMB in clinical practice.

Relevance of 2'-O-Methylation and Pseudouridylation for the Malignant Melanoma

Simple Summary

This study investigates the expression, the histological localization, and the influence of the factors involved in 2′-O-methylation and pseudouridylation on prognostic relevant markers, proliferation markers, overall survival, molecular immune surveillance and evasion mechanisms within the malignant melanoma. Statistically significant positive correlations to the expression of markers involved in cell proliferation were observed. The upregulation of the RNA modifying factors was of prognostic relevance in this tumor disease with a negative impact on the overall survival of melanoma patients. Furthermore, the factors involved in 2′-O-methylation and pseudouridylation were statistically significant negative correlated to the expression of human leukocyte antigen class I genes as well as of components of the antigen processing machinery.

Abstract

The two RNA modifications 2′-O-methylation and pseudouridylation occur on several RNA species including ribosomal RNAs leading to an increased translation as well as cell proliferation associated with distinct functions. Using malignant melanoma (MM) as a model system the proteins mediating these RNA modifications were for the first time analyzed by different bioinformatics tools and public available databases regarding their expression and histological localization. Next to this, the impact of these RNA-modifying factors on prognostic relevant processes and marker genes of malignant melanoma was investigated and correlated to immune surveillance and evasion strategies. The RNA modifying factors exerted statistically significant positive correlations to the expression of genes involved in cell proliferation and were statistically significant negative correlated to the expression of human leukocyte antigen class I genes as well as of components of the antigen processing machinery in malignant melanoma. Upregulation of the RNA modifying proteins was of prognostic relevance in this tumor disease with a negative impact on the overall survival of melanoma patients. Furthermore, the expression of known oncogenic miRs, which are induced in malignant melanoma, directly correlated to the expression of factors involved in these two RNA modifications.

WNT11-FZD7-DAAM1 signalling supports tumour initiating abilities and melanoma amoeboid invasion

Melanoma is a highly aggressive tumour that can metastasize very early in disease progression. Notably, melanoma can disseminate using amoeboid invasive strategies. We show here that high Myosin II activity, high levels of ki-67 and high tumour-initiating abilities are characteristic of invasive amoeboid melanoma cells. Mechanistically, we find that WNT11-FZD7-DAAM1 activates Rho-ROCK1/2-Myosin II and plays a crucial role in regulating tumour-initiating potential, local invasion and distant metastasis formation. Importantly, amoeboid melanoma cells express both proliferative and invasive gene signatures. As such, invasive fronts of human and mouse melanomas are enriched in amoeboid cells that are also ki-67 positive. This pattern is further enhanced in metastatic lesions. We propose eradication of amoeboid melanoma cells after surgical removal as a therapeutic strategy.

Functional Roles of Matrix Metalloproteinases and Their Inhibitors in Melanoma

The extracellular matrix (ECM) plays an important role in the regulation of the tissue microenvironment and in the maintenance of cellular homeostasis. Several proteins with a proteolytic activity toward several ECM components are involved in the regulation and remodeling of the ECM. Among these, Matrix Metalloproteinases (MMPs) are a class of peptidase able to remodel the ECM by favoring the tumor invasive processes. Of these peptidases, MMP-9 is the most involved in the development of cancer, including that of melanoma. Dysregulations of the MAPKs and PI3K/Akt signaling pathways can lead to an aberrant overexpression of MMP-9. Even ncRNAs are implicated in the aberrant production of MMP-9 protein, as well as other proteins responsible for the activation or inhibition of MMP-9, such as Osteopontin and Tissue Inhibitors of Metalloproteinases. Currently, there are different therapeutic approaches for melanoma, including targeted therapies and immunotherapies. However, no biomarkers are available for the prediction of the therapeutic response. In this context, several studies have tried to understand the diagnostic, prognostic and therapeutic potential of MMP-9 in melanoma patients by performing clinical trials with synthetic MMPs inhibitors. Therefore, MMP-9 may be considered a promising molecule for the management of melanoma patients due to its role as a biomarker and therapeutic target.

Automated quantification of Ki67/MART1 stains may prevent false-negative melanoma diagnoses

BACKGROUND

Inability to distinguish melanomas from benign nevi is the most frequent reason for malpractice lawsuits in surgical pathology. Reliable diagnostic tools to support hematoxylin and eosin (H&E) stains and induce diagnostic vigilance are thus highly needed. Because high diagnostic performance recently was showed using automated image analysis, the immunohistochemical proliferation marker Ki67 seems a potential candidate. This study aimed to investigate if this previously presented automated algorithm could have prevented 10 false-negative melanoma diagnoses. In addition, diagnostic utility of another, but narrower, immunohistochemical proliferation marker, phosphohistone H3 (PHH3), was explored.

METHODS

A total of 10 formalin-fixed paraffin-embedded melanocytic tumors, initially classified as benign or dysplastic but revised as melanomas at metastatic debut, were dual-stained for Ki67/MART1 and PHH3/MART1. A Ki67 index was automatically calculated in epidermis, dermis, a combination of such, and a dermal hot spot. Dermal PHH3/MART1 scores were established semi-automatically.

RESULTS

The dermal Ki67 index identified all 10 melanomas, the hot-spot index 8 and the epidermal and combined indices only 2 and 5, respectively. Nine melanomas were PHH3 positive and scores correlated with Ki67.

CONCLUSIONS

PHH3 added limited information, but supplemental automated Ki67 assessment could possibly have prevented the misdiagnosis of most melanomas had the algorithm been available at the time of diagnosis.

Dormancy of growth-stunted malignant melanoma: sustainable and smoldering patterns

The presentations of primary and metastatic cutaneous malignant melanoma (CMM) are very diverse. Evidence increasingly indicates that single CMM cells spread to distant sites quite early during cancer progression and are soon eliminated before they become clinically detectable. However bulky metastases which appear at a later stage might derive from some of these early neoplastic cells. It seems that local CMM single cell micro-metastases commonly predict sentinel lymph node involvement without overtly reflecting CMM progression to bulky visceral metastases. This study is intended to review the current understanding of the mechanisms underlying two CMM presentations. The first is the long interval, apparently disease-free, with persistent CMM dormancy, which may precede overt metastatic growth. Immunosurveillance may induce dormancy in single CMM cells disseminated in the body by blocking their proliferation cycle. The second is the so-called CMM smoldering phenomenon, which is marked by an alternate progression and regression of CMM locally with metastases that wax and wane for long periods of time over restricted skin areas. These very diverse patterns of CMM progression are likely to be ascribable to a number of biological factors, including the activation of CMM stem cells, and the combined phenotypic heterogeneity and variability in proliferative amplification in CMM cell clusters. Furthermore an adequate stimulation of CMM immune-surveillance and the induction of a specific stromal structure and vascular response are required. In this context, most early CMM tumors are in part controlled by lymphocyte-mediated responses before they become clinically detectable. However both the role of immune-surveillance and the mechanisms underlying both persistent and smoldering CMM dormancy remain unclear.

In vivo skin fluorescence imaging in young Caucasian adults with early malignant melanomas

Background

Human cutaneous malignant melanoma (CMM) is an aggressive cancer showing a dramatic worldwide increase in incidence over the past few decades. The most prominent relative epidemiological increase has been disclosed in young women. The aim of the study was to assess the effects of chronic sun exposures in order to rate the extend of melanocytic stimulations in the vicinity of CMM.

Methods

The study was designed to evaluate the melanin distribution and density using ultraviolet light illumination. The present study was performed on surgical excision specimens of thin CMM lesion removed from the upper limbs of 55 Caucasian adults (37 women and 18 men). Two control groups comprised 23 men and 21 women of similar ages who had medium-size congenital melanocytic nevi, also present on the upper limbs. The peritumoral skin was scrutinized using a Visioscan^® VC98 device, revealing the faint mosaic melanoderma (FMM) pattern that grossly indicates early signs of chronic photodamage in epidermal melanin units.

Results

The median extent of relative FMM was significantly higher in the CMM male group. By contrast, the CMM female group showed a reverse bimodal distribution in FMM size. Only 12/37 (32.5%) of the CMM female group had an increased FMM size, whereas 25/37 (67.5%) of females with CMM had a global FMM extent in the normal range, relative to the controls.

Conclusion

Thin CMM supervening in young women appear unrelated to repeat photoexposure. Other mechanisms are possibly involved.

Cell cycle analysis can differentiate thin melanomas from dysplastic nevi and reveals accelerated replication in thick melanomas

Cell replication integrates aberrations of cell cycle regulation and diverse upstream pathways which all can contribute to melanoma development and progression. In this study, cell cycle regulatory proteins were detected in situ in benign and malignant melanocytic tumors to allow correlation of major cell cycle fractions (G1, S-G2, and G2-M) with melanoma evolution. Dysplastic nevi expressed early cell cycle markers (cyclin D1 and cyclin-dependent kinase 2; Cdk2) significantly more (p < 0.05) than common nevi. Post-G1 phase markers such as cyclin A, geminin, topoisomerase IIα (peaking at S-G2) and aurora kinase B (peaking at G2-M) were expressed in thin (≤1 mm) melanomas but not in dysplastic nevi, suggesting that dysplastic melanocytes engaged in the cell cycle do not complete replication and remain arrested in G1 phase. In malignant melanomas, the expression of general and post-G1 phase markers correlated well with each other implying negligible cell cycle arrest. Post-G1 phase markers and Ki67 but none of the early markers cyclin D1, Cdk2 or minichromosome maintenance protein 6 (Mcm6) were expressed significantly more often in thick (>1 mm) than in thin melanomas. Marker expression did not differ between metastatic melanomas and thick melanomas, with the exception of aurora kinase A of which the expression was higher in metastatic melanomas. Combined detection of cyclin A (post-G1 phase) with Mcm6 (replication licensing) and Ki67 correctly classified thin melanomas and dysplastic nevi in 95.9 % of the original samples and in 93.2 % of cross-validated grouped cases at 89.5 % sensitivity and 92.6 % specificity. Therefore, cell cycle phase marker detection can indicate malignancy in early melanocytic lesions and accelerated cell cycle progression during vertical melanoma growth.

Proliferation indices of phosphohistone H3 and Ki67: strong prognostic markers in a consecutive cohort with stage I/II melanoma

Cellular proliferation is correlated with the progression of melanoma. Accordingly, the proliferation index of H&E-stained thin melanomas was recently included in the staging system of the American Joint Committee on Cancer. Yet, the immunohistochemical markers of proliferation phosphohistone H3 and Ki67 may improve such indices. To accurately quantify these markers, they should be combined with a melanocytic marker, for example, MART1 in an immunohistochemical double stain; also enabling automated quantification by image analysis. The aim of the study was to compare the prognostic impact of phosphohistone H3/MART1, Ki67/MART1, and H&E stains in primary cutaneous melanoma, and to determine the difference between indices established in hot spots and the global tumor areas. The study included 153 consecutive stage I/II melanoma-patients. The follow-up time was 8-14 years for event-free melanoma. Recurrent disease occurred in 43 patients; 37 died of melanoma. Both events occurred in only three thin melanomas. Their paraffin-embedded tissue was stained for phosphohistone H3/MART1, Ki67/MART1, and with H&E. And proliferation indices were established in 1-mm(2) hot spots and in the global tumor areas. In multivariate Cox analyses, only hot spot indices of phosphohistone H3/MART1 and Ki67/MART1 were independent prognostic markers. Phosphohistone H3/MART1 tended to be better than Ki67/MART1 with adjusted hazard ratios of 3.66 (95% CI, 1.40-9.55; P=0.008) for progression-free survival and 3.42 (95% CI, 1.29-9.04; P=0.013) for melanoma-specific death. In all stains, prognostic performance was substantially improved by using hot spots instead of the global tumor areas. In conclusion, phosphohistone H3/MART1 and Ki67/MART1 were superior to H&E stains, and hot spots superior to the global tumor areas. Given the potential for automated analysis, these double stains seem to be robust alternatives to conventional mitotic detection by H&E in stage I/II melanomas in general. This was particularly true for thick melanomas whereas no specific analyses for thin melanomas only could be performed.

HOX Gene Aberrant Expression in Skin Melanoma: A Review

The homeobox family and its subset of HOX gene products represent a family of transcription factors directing DNA-protein and protein-protein interactions. In the embryo, they are central regulators in cell differentiation during morphogenesis. A series of genes of the four HOX gene clusters A, B, C, and D were reported to show aberrant expressions in oncogenesis, particularly in cutaneous malignant melanoma (CMM). They are involved in cell proliferation and progression in the CMM metastatic path. We present relevant peer-reviewed literature findings about the aberrant expression of HOX genes in CMM. The number of CMM cell nuclei exhibiting aberrant HOX protein expression appears correlated with tumour progression.

Malignant melanoma and its stromal nonimmune microecosystem

In recent years, rapid advances were reached in the understanding of a series of biologic signals influencing cutaneous malignant melanoma (CMM) cells. CMM is in close contact with a peculiar dermal extracellular matrix (ECM). Stromal cells store and release various structural ECM components. The impact on CMM growth and progression is mediated through strong and long-lasting effects of ECM products. This paper summarizes some peculiar aspects of the peri-CMM stroma showing intracytoplasmic loads in Factor XIIIa, CD34, versican, and α (IV) collagen chains. The restricted peri-CMM skin territory exhibiting such changes corresponds to the area showing neoangiogenesis and extravascular unicellular metastatic spread. The latter inconspicuous migratory CMM cells possibly correspond to CMM stem cells or to CMM cells with aberrant HOX gene expression. Their presence is associated with an increased risk for metastases in the regional sentinel lymph nodes. In conclusion, the CMM-stroma connection appears crucial to the growth regulation, invasiveness and initial metastatic spread of CMM cells. Although much remains to be learned in this field, the active intervention of the peri-CMM stroma is likely involved in the inconspicuous early metastatic migration of CMM cells.