Differential expression of matrix metalloproteinase-2 by fibroblasts in co-cultures with keratinocytes, basal cell carcinoma and melanoma

Matrix Effectors in the Pathogenesis of Keratinocyte-Derived Carcinomas

Basal cell carcinoma (BCC) and cutaneous squamous cell carcinoma (cSCC), referred to as keratinocyte carcinomas, are skin cancer with the highest incidence. BCCs, rarely metastasize; whereas, though generally not characterized by high lethality, approximately 2–4% of primary cSCCs metastasize with patients exhibiting poor prognosis. The extracellular matrix (ECM) serves as a scaffold that provides structural and biological support to cells in all human tissues. The main components of the ECM, including fibrillar proteins, proteoglycans (PGs), glycosaminoglycans (GAGs), and adhesion proteins such as fibronectin, are secreted by the cells in a tissue-specific manner, critical for the proper function of each organ. The skin compartmentalization to the epidermis and dermis compartments is based on a basement membrane (BM), a highly specialized network of ECM proteins that separate and unify the two compartments. The stiffness and assembly of BM and tensile forces affect tumor progenitors' invasion at the stratified epithelium's stromal border. Likewise, the mechanical properties of the stroma, e.g., stiffness, are directly correlated to the pathogenesis of the keratinocyte carcinomas. Since the ECM is a pool for various growth factors, cytokines, and chemokines, its' intense remodeling in the aberrant cancer tissue milieu affects biological functions, such as angiogenesis, adhesion, proliferation, or cell motility by regulating specific signaling pathways. This review discusses the structural and functional modulations of the keratinocyte carcinoma microenvironment. Furthermore, we debate how ECM remodeling affects the pathogenesis of these skin cancers.

Current Perspectives on the Role of Matrix Metalloproteinases in the Pathogenesis of Basal Cell Carcinoma

Basal cell carcinoma (BCC) is the most common skin malignancy, which rarely metastasizes but has a great ability to infiltrate and invade the surrounding tissues. One of the molecular players involved in the metastatic process are matrix metalloproteinases (MMPs). MMPs are enzymes that can degrade various components of the extracellular matrix. In the skin, the expression of MMPs is increased in response to various stimuli, including ultraviolet (UV) radiation, one of the main factors involved in the development of BCC. By modulating various processes that are linked to tumor growth, such as invasion and angiogenesis, MMPs have been associated with UV-related carcinogenesis. The sources of MMPs are multiple, as they can be released by both neoplastic and tumor microenvironment cells. Inhibiting the action of MMPs could be a useful therapeutic option in BCC management. In this review that reunites the latest advances in this domain, we discuss the role of MMPs in the pathogenesis and evolution of BCC, as molecules involved in tumor aggressiveness and risk of recurrence, in order to offer a fresh and updated perspective on this field.

Matrix metalloproteinases in keratinocyte carcinomas

The incidence of cutaneous keratinocyte-derived cancers is increasing globally. Basal cell carcinoma (BCC) is the most common malignancy worldwide, and cutaneous squamous cell carcinoma (cSCC) is the most common metastatic skin cancer. BCC can be classified into subtypes based on the histology, and these subtypes are classified further into low- and high-risk tumors. There is an increasing need to identify new therapeutic strategies for the treatment of unresectable and metastatic cSCC, and for aggressive BCC variants such as infiltrating, basosquamous or morpheaform BCCs. The most important risk factor for BCC and cSCC is solar UV radiation, which causes genetic and epigenetic alterations in keratinocytes. Similar gene mutations are noted already in sun-exposed normal skin emphasizing the role of the alterations in the tumor microenvironment in the progression of cSCC. Early events in cSCC progression are alterations in the composition of basement membrane and dermal extracellular matrix induced by influx of microbes, inflammatory cells and activated stromal fibroblasts. Activated fibroblasts promote inflammation and produce growth factors and proteolytic enzymes, including matrix metalloproteinases (MMPs). Transforming growth factor-β produced by tumor cells and fibroblasts induces the expression of MMPs by cSCC cells and promotes their invasion. Fibroblast-derived keratinocyte growth factor suppresses the malignant phenotype of cSCC cells by inhibiting the expression of several MMPs. These findings emphasize the importance of interplay of tumor and stromal cells in the progression of cSCC and BCC and suggest tumor microenvironment as a therapeutic target in cSCC and aggressive subtypes of BCC.

UVA, metabolism and melanoma: UVA makes melanoma hungry for metastasis

Ultraviolet (UV) radiation has a plethora of effects on human tissues. In the UV spectrum, wavelengths above 320 nm fall into the UVA range, and for these, it has been shown that they induce reactive oxygen species (ROS), DNA mutations and are capable to induce melanoma in mice. In addition to this, it was recently shown that UVA irradiation and UVA-induced ROS also increase glucose metabolism of melanoma cells. UVA irradiation causes a persistent increase in glucose consumption, accompanied by increased glycolysis, increased lactic acid production and activation of the pentose phosphate pathway. Furthermore, it was shown that the enhanced secretion of lactic acid is important for invasion of melanoma in vitro. The current knowledge of this link between UVA, metabolism and melanoma, possible mechanisms of UVA-induced glucose metabolism and their starting points are discussed in this review with focus on ROS- and UVA-induced cellular stress signalling, DNA damage signalling and DNA repair systems. When looking at the benefits of UVA-induced glucose metabolism, it becomes apparent that there are more advantages of these metabolic changes than one would expect. Besides the role of lactic acid as initiator of protease expression and invasion, its role for immune escape of melanoma cells and the pentose phosphate pathway-derived nicotinamide adenine dinucleotide phosphate (NADPH) as part of a ROS detoxification strategy are discussed.

Expression of metalloproteinases (MMP-2 and MMP-9) in basal-cell carcinoma

The aim of this study was to compare the expressions of mRNA for metalloproteinases (MMP-2 and MMP-9) and type IV collagen in two different histological types of basal-cell carcinoma (BCCs; nodular and infiltrative) and in normal tissues from the tumor interface. The study included biopsy specimens of the skin involved with BCC and normal skin adjacent the lesion. The expressions of mRNA for MMP-2, MMP-9 and type IV collagen were determined by means of RT-PCR (Reverse transcription polymerase chain reaction). The level of type IV collagen mRNA in nodular and infiltrative BCCs turned out to be significantly lower, and the expressions of MMP-2 and MMP-9 mRNA significantly higher than in normal tissues adjacent to these tumors. The expression of mRNA for MMP-9 but not for MMP-2 was significantly higher in infiltrative BCCs than in the nodular BCCs. In turn, normal tissues adjacent to nodular BCCs showed significantly higher levels of mRNA for MMP-2 and significantly lower levels of type IV collagen mRNA than the normal tissues from the interface of infiltrative BCCs. The findings suggest that MMP-2 and MMP-9 could be used as prognostic factors of BCCs.

Role of Matrix Metalloproteinases in Photoaging and Photocarcinogenesis

Matrix metalloproteinases (MMPs) are zinc-containing endopeptidases with an extensive range of substrate specificities. Collectively, these enzymes are able to degrade various components of extracellular matrix (ECM) proteins. Based on their structure and substrate specificity, they can be categorized into five main subgroups, namely (1) collagenases (MMP-1, MMP-8 and MMP-13); (2) gelatinases (MMP-2 and MMP-9); (3) stromelysins (MMP-3, MMP-10 and MMP-11); (4) matrilysins (MMP-7 and MMP-26); and (5) membrane-type (MT) MMPs (MMP-14, MMP-15, and MMP-16). The alterations made to the ECM by MMPs might contribute in skin wrinkling, a characteristic of premature skin aging. In photocarcinogenesis, degradation of ECM is the initial step towards tumor cell invasion, to invade both the basement membrane and the surrounding stroma that mainly comprises fibrillar collagens. Additionally, MMPs are involved in angiogenesis, which promotes cancer cell growth and migration. In this review, we focus on the present knowledge about premature skin aging and skin cancers such as basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and melanoma, with our main focus on members of the MMP family and their functions.

Regulation of fibroblast gene expression by keratinocytes in organotypic skin culture provides possible mechanisms for the antifibrotic effect of reepithelialization

To investigate the mechanisms behind the antifibrotic effect associated with epidermal regeneration, the expression of 12 fibroblast genes important for the modulation of the extracellular matrix (ECM), as well as α-smooth muscle actin, was studied in a keratinocyte-fibroblast organotypic skin culture model. The study was performed over time during epidermal generation and in the presence or absence of the profibrotic factor transforming growth factor-β. the Presence of epidermal differentiation markers in the model was essentially coherent with that of native skin. Fibroblast gene expression was analyzed with real-time polymerase chain reaction after removal of the epidermal layer. After 2 days of air-exposed culture, 11 out of the 13 genes studied were significantly regulated by keratinocytes in the absence or presence of transforming growth factor-β. The regulation of connective tissue growth factor, collagen I and III, fibronectin, plasmin system regulators, matrix metalloproteinases and their inhibitors as well as α-smooth muscle actin was consistent with a suppression of ECM formation or contraction. Overall, the results support a view that keratinocytes regulate fibroblasts to act catabolically on the ECM in epithelialization processes. This provides possible mechanisms for the clinical observations that reepithelialization and epidermal wound coverage counteract excessive scar formation.

Melanoma associated spongiform scleropathy: characterization, biochemical and immunohistochemical studies

SUMMARY

Melanoma associated spongiform scleropathy (MASS) is a non-inflammatory scleral change with a spongiotic morphology seen in association with uveal melanoma. MASS is seen as whitish spindle shaped areas within the sclera that is adjacent to and in contact with a choroidal or ciliary body melanoma. This change can be seen as small scattered lesions in the inner scleral layers or as extensive areas along the whole extent of contact between the tumour and the sclera and involves most of the scleral thickness. MASS changes of different grades of severity were seen in 38% of 363 melanoma eyes investigated. The presence of MASS showed a statistical correlation with age. A significant high incidence of MASS was found in old age groups. This might due to the fact that MASS needs a longer period of contact between the tumour and the sclera to develop. It is also possible that age-related changes of the extracellular matrix might alter its response to melanoma produced factors leading to the development of MASS. The development of MASS and its severity are influenced by the extent of contact between the tumour and the sclera. This is supported by the significant statistical relation between the largest basal diameter of the tumours and the severity of MASS. Statistical correlation was found between MASS and scleral and extrascleral tumour extension. More than 90% of 82 specimens that showed tumour extension were associated with MASS. A biochemical analysis of scleral samples taken from areas with severe MASS showed a significant reduction of the main amino acids of collagen type I, which is the main scleral collagen. The amounts of total scleral proteins were significantly reduced. This scleral protein reduction is associated with an increase in glycosaminoglycans. These findings indicate a collagen degradation process. Immunohistochemical studies were performed to investigate the expression of matrix metalloproteinases (MMPs). In situ hybridization showed a significantly more frequent and more intense expression of MMP-2 by scleral fibroblasts in areas with MASS compared with areas without MASS. This was also seen by immunohistochemical staining. Similar high frequency and intense expression of MMP-2 were seen in tumour infiltrating macrophages. The results of biochemical and immunohistochemical studies indicate a collagen degradation process. This degradation may be the result of the proteolytic enzyme MMP-2 expressed by scleral fibroblasts under the effect of tumour humeral factors and/or tumour infiltrating macrophages. This scleral degradation results in fragmentation of the scleral collagen fibrils. This along with the accumulation of water in the sclera, as a result of the increase in the production of glycosaminoglycans, results in increase of scleral thickness in MASS areas and forms the histopathological picture of MASS. The scleral degradation may facilitate tumour invasion and may explain the statistical relation between MASS and scleral tumour invasion. MASS was found in a few of the eyes that had received pre-enucleation radiation. The possible explanation is that radiation might cause destruction of scleral fibroblasts reducing their ability to produce MMP-2, thus decreasing the development of MASS. No relation between MASS and survival was found. This is probably explained by the fact that the main cause of death due to uveal melanoma is distant metastasis. MASS changes are found to be associated with local tumour invasion but not statistically correlated to survival.

High numbers of human skin cancers express MMP2 and several integrin genes

BACKGROUND

Basal cell carcinomas (BCC), squamous cell carcinomas (SCC) and cutaneous malignant melanoma (MM) are solid skin cancers derived from different cell types, with different ability to metastasize. Several subtypes of integrins and matrix metalloproteinases (MMP) have been related to malignization and metastasis processes. This work aimed at a quantitative evaluation of skin cancers expressing eight integrins and MMP2 genes.

METHODS

Expression of integrins and MMP2 genes was evaluated on fresh tumor biopsies from BCC, SCC and MM, and respective controls, by the reverse transcriptase polychain reaction (RT-PCR) technique.

RESULTS

More than 90% tumors expressed alpha6a, beta1, beta3 and beta6 (non-melanoma), and alpha5a, alpha6a and MMP2 (MM). Up to 100% controls also expressed beta1 and beta3. The results were significant for alpha6a in BCC (p = 0.026), alpha6b in SCC (p = 0.035), alpha2a in BCC (p = 0.003), beta5 and beta6 in BCC (p = 0.005). MMP2 was expressed in 100% MM (p = 0.0004).

CONCLUSION

Integrin subunits alpha2a and alpha6a would be interesting targets for BCC anti-tumor therapy, as well as alpha6b in case of SCC. The elevated number of BCC expressing alpha2 and alpha6, and of MM expressing alphav and MMP2, corroborate literature data.