Prognostic significance of p53 over-expression in thin melanomas

Immunohistochemistry as an accurate tool for the assessment of BRAF V600E and TP53 mutations in primary and metastatic melanoma

Metastatic melanoma is a fatal disease with poor prognosis. Ever since targeted therapy against oncogenic BRAF was approved, molecular profiling has become an integral part of the management of such patients. While molecular testing is not available in all pathology laboratories, immunohistochemistry (IHC) is a reliable screening option. The major objective of the present study was to evaluate whether IHC detection of BRAF and the tumor (suppressor) protein 53 gene (TP53) are reliable surrogates for mutation detection. Formalin-fixed paraffin-embedded samples of melanomas for which molecular data were previously obtained by targeted next-generation sequencing (NGS) between January 2014 and February 2019 were immunostained with BRAF V600E and p53 antibodies. A blinded evaluation of the IHC slides was performed by two pathologists in order to evaluate inter-observer concordance (discordant cases were reviewed by a third observer). The associations between the results of IHC and molecular profiling were evaluated. The study included a series of 37 cases of which 15 harbored a BRAF mutation and five a TP53 mutation. IHC had an overall diagnostic accuracy of 93.9% for BRAF V600E and 68.8% for TP53 compared to NGS. A statistically significant association between the two diagnostic methods was obtained for BRAF V600E (P=0.0004) but not for p53 (P=0.3098) IHC. The κ coefficient for IHC assessment of p53 was 0.55 and that for BRAF V600E was 0.72. In conclusion, the present results evidenced that IHC staining is a reliable surrogate for NGS in identifying the BRAF V600E mutation, which may become an efficient screening tool. Aberrant expression of p53 on IHC is at times associated with TP53 mutations but it was not possible to establish a direct link.

p53 prevents progression of nevi to melanoma predominantly through cell cycle regulation

p53 is the central member of a critical tumor suppressor pathway in virtually all tumor types, where it is silenced mainly by missense mutations. In melanoma, p53 predominantly remains wild type, thus its role has been neglected. To study the effect of p53 on melanocyte function and melanomagenesis, we crossed the ‘high-p53’Mdm4+/− mouse to the well-established TP-ras0/+ murine melanoma progression model. After treatment with the carcinogen dimethylbenzanthracene (DMBA), TP-ras0/+ mice on the Mdm4+/− background developed fewer tumors with a delay in the age of onset of melanomas compared to TP-ras0/+ mice. Furthermore, we observed a dramatic decrease in tumor growth, lack of metastasis with increased survival of TP-ras0/+: Mdm4+/− mice. Thus, p53 effectively prevented the conversion of small benign tumors to malignant and metastatic melanoma. p53 activation in cultured primary melanocyte and melanoma cell lines using Nutlin-3, a specific Mdm2 antagonist, supported these findings. Moreover, global gene expression and network analysis of Nutlin-3-treated primary human melanocytes indicated that cell cycle regulation through the p21WAF1/CIP1 signaling network may be the key anti-melanomagenic activity of p53.

Understanding spitzoid tumours: new insights from molecular pathology

Spitzoid tumours are a morphologically diverse group of lesions that share histological similarity to the Spitz naevus, a benign melanocytic skin tumour. Distinguishing classic Spitz naevi from cutaneous malignant melanoma is usually achievable on standard histology sections, but occasionally equivocal lesions are encountered that show features intermediate between these two entities and consequently generate considerable clinical and histopathological concern. The nomenclature and diagnostic criteria for spitzoid lesions are not standardized and this article begins by considering the adverse effect this has on our understanding of spitzoid tumour biology. Investigations of some of the hallmark features of cancer and neoplasia in spitzoid tumours are described, and the contribution of these studies to our understanding of spitzoid tumour biology is considered, along with their potential diagnostic utility. These studies compare spitzoid tumours with better-characterized melanocytic lesions, and from such comparisons assumptions concerning the biological nature of different spitzoid tumours can be made. In contrast, investigations of the mitogen-activated protein kinase (MAPK) pathway and DNA gains and losses have suggested that Spitz naevi may be genetically distinct from other melanocytic tumours. The studies that led to this conclusion are reviewed, as well as subsequent work examining whether the same applies to all spitzoid tumours. Possible explanations for the considerable inconsistencies within some of these data are explored. Finally, potential pathways of tumour progression within spitzoid lesions are considered, with an emphasis placed upon insights gained from investigations of MAPK genes and DNA gains and losses.

The role of p53 in pigmentation, tanning and melanoma

p53 has a central role in skin pigmentation and may impact on melanoma at all stages, however, as it's mutation frequency in melanoma is low, it's role has been somewhat under-appreciated. During normal skin function, p53 in the keratinocyte is a transducer of the skin tanning signal and an essential component of what is effectively a keratinocyte-melanocyte signaling cycle that regulates skin pigmentation. It is clear that this cycle functions optimally in skin of dark pigmentation. When melanin biosynthesis is genetically disrupted in skin of white complexion, we propose that this cycle operates as a promoter of melanocyte proliferation. The cell autonomous function of p53 in melanocytes is not well described, however, the balance of the evidence suggests that p53 is an effective tumor suppressor and the myriad of mechanisms by which the p53 pathway may be dysregulated in tumors attests to it importance as a tumor suppressor. In this review, we outline the known mechanisms that impair p53 itself and its immediate regulators or target genes during melanomagenesis. Due to the importance of this pathway, it is clear that p53 disruptions may relate directly to a patient's prognosis. This pathway will continue to be a focus of investigation, particularly with respect to targeted experimental chemotherapeutics.

Downregulation of cell cycle modulators p21, p27, p53, Rb and proapoptotic Bcl-2-related proteins Bax and Bak in cutaneous melanoma is associated with worse patient prognosis: preliminary findings

BACKGROUND

Cutaneous melanoma is a tumor with high metastatic potential, but the mechanisms leading to progression are still not fully understood. To provide further molecular basis for understanding the progression of melanoma, the aim of this study was to examine the expression pattern of cell cycle modulators (p21, p27, p53 and Rb) and proapoptotic multidomain Bcl-2 related proteins (Bax and Bak) and to analyze its differences in patients with and without progression stages.

METHODS

We have studied 31 patients with cutaneous melanoma at stage IIa (Breslow thickness 1.5-4.0 mm), and follow them for 10-year period. Eighteen of these patients developed metastasis. The determination of selected molecular markers participating in cell cycle regulation and apoptosis was performed by immunohistochemistry.

RESULTS

We have observed a significant increase in the loss of expression of the Bax, Bak, p21, p27, p53 and Rb. The analysis of the relationship between these downregulated markers and Breslow thickness showed significant positive correlation (r=0.556, p=0.029) and predictive value if thickness below 2.3 mm (OR=3.0, 95% CI=0.312-28.84).

CONCLUSIONS

Our study showed that the downregulation of the markers associated with cell cycle control and apoptosis is of great value in predicting malignant transformation and in assessing the risk of metastases development for 10-year follow-up period.

The role of cell cycle regulatory proteins in the pathogenesis of melanoma

The transformation of melanocytes to melanoma cells is characterised by abnormal proliferation resulting from alterations in cell cycle regulatory mechanisms. This occurs through alterations in the two major cell cycle regulatory pathways, the retinoblastoma (Rb) and p53 tumour suppressor pathways. This review summarises the current knowledge of alterations in these two pathways at G1/S transition and specifically the role of the key cell cycle regulatory proteins pRb, p16INK4a (p16), cyclin D1, p27Kip1 (p27), p53 and p21Waf1/Cip1 (p21) in the pathogenesis of melanoma. It also considers their prognostic significance. Current data indicate that alterations of cyclin kinase inhibitor (cdki) levels are implicated in the pathogenesis of melanoma and may be useful prognostic markers. However, large validation studies linked to comprehensive clinical follow up data are necessary to clarify the prognostic significance of cell cycle regulatory proteins in individual patients.

Etiologic factors associated with p53 immunostaining in cutaneousmalignant melanoma

Findings from a case-control study of cutaneous malignant melanoma (CMM) in Queensland, Australia, suggest that melanomas exhibiting p53 immunostaining possess different risk factors from those of other melanomas. To further explore this hypothesis, a case-only analysis of risk factors for p53 immunostaining with anti-p53 MAb DO-7 was undertaken in 523 people diagnosed with CMM in Canada and Australia. Phenotypic factors and past sun exposure were measured using a self-administered questionnaire and telephone interview. The presence of strong p53 staining (>10% of cell nuclei positively stained vs. <1% staining) was positively associated with some indicators of high cumulative sun exposure: lentigo maligna melanoma subtype (OR = 3.2 vs. superficial spreading subtype), melanoma location on the head and neck (OR = 2.8 vs. back), histopathologic evidence of solar elastosis (OR = 2.1) and previous diagnosis of nonmelanoma skin cancer (OR = 2.4). Strong staining was negatively associated with high nevus density on the back (OR = 0.2 for >25 nevi vs. 0-3 nevi) and histologic evidence of a coexisting nevus (OR = 0.3). Other factors associated with strong p53 immunostaining include greater Breslow thickness (OR = 7.4 for >4.00 vs. <0.76 mm), male sex (OR = 2.2) and dense freckling (OR = 6.6 vs. few freckles). Of these, thickness, male sex, dense freckling, low nevus density on the back, histologic subtype and history of nonmelanoma skin cancer appeared to be independently associated with strong p53 staining. Our findings are consistent with the Queensland study in suggesting that variables indicating high accumulated sun exposure are positively associated with p53 staining and that an increased number of nevi is positively associated with its absence; they may reflect etiologic and pathogenetic heterogeneity in melanoma.

The TP53 Tumor Suppressor Gene and Melanoma Tumorigenesis: Is There a Relationship?

Mutations in the TP53 gene are found in about 11% of melanomas. Although nearly 600 papers have been published with varying degrees of consensus, there does not appear to be any comparable analysis that facilitates more than a glimpse into the role of p53 in melanomagenesis. This article reviews p53 alterations (at the gene and protein levels) in melanocytic skin lesions and discusses the following points: (i) p53 alterations commence as early as at the stage of benign and dysplastic nevi; (ii) these alterations are frequent in melanomas, and gradually increase with their progression; (iii) there is no concordance between the frequent p53 protein expression and the rarity of both TP53 gene mutations in melanomas, and (iv) the entire p53 pathway is a more critical determinant of the fate of the melanocytic skin lesions than the status of the p53 protein or the gene itself.

Nuclear PTEN expression and clinicopathologic features in a population-based series of primary cutaneous melanoma

Germline mutations of the PTEN tumor-suppressor gene, on 10q23, cause Cowden syndrome, an inherited hamartoma syndrome with a high risk of breast, thyroid and endometrial carcinomas and, some suggest, melanoma. To date, most studies which strongly implicate PTEN in the etiology of sporadic melanomas have depended on cell lines, short-term tumor cultures and noncultured metastatic melanomas. The only study which reports PTEN protein expression in melanoma focuses on cytoplasmic expression, mainly in metastatic samples. To determine how PTEN contributes to the etiology or the progression of primary cutaneous melanoma, we examined cytoplasmic and nuclear PTEN expression against clinical and pathologic features in a population-based sample of 150 individuals with incident primary cutaneous melanoma. Among 92 evaluable samples, 30 had no or decreased cytoplasmic PTEN protein expression and the remaining 62 had normal PTEN expression. In contrast, 84 tumors had no or decreased nuclear expression and 8 had normal nuclear PTEN expression. None of the clinical features studied, such as Clark's level and Breslow thickness or sun exposure, were associated with cytoplasmic PTEN expressional levels. An association with loss of nuclear PTEN expression was indicated for anatomical site (p = 0.06) and mitotic index (p = 0.02). There was also an association for melanomas to either not express nuclear PTEN or to express p53 alone, rather than both simultaneously (p = 0.02). In contrast with metastatic melanoma, where we have shown previously that almost two-thirds of tumors have some PTEN inactivation, only one-third of primary melanomas had PTEN silencing. This suggests that PTEN inactivation is a late event likely related to melanoma progression rather than initiation. Taken together with our previous observations in thyroid and islet cell tumors, our data suggest that nuclear-cytoplasmic partitioning of PTEN might also play a role in melanoma progression.

The novel tumour suppressor gene ING1 is overexpressed in human melanoma cell lines

BACKGROUND

Epidemiological evidence indicates that exposure to ultraviolet (UV) radiation is directly linked to the increase of both incidence and mortality of melanoma. However, the genetic changes caused by UV radiation that lead to melanoma formation remain poorly understood. Recently, a potential tumour suppressor gene ING1 (inhibitor of growth 1) was shown to inhibit cell growth and induce apoptosis in the presence of p53. We have demonstrated that the expression of ING1 is induced after UV irradiation and that ING1 enhances the repair of UV-damaged DNA.

OBJECTIVES

To investigate if ING1 plays a role in melanoma formation.

METHODS

We examined p33ING1 expression levels in 14 melanoma cell lines.

RESULTS

We found that p33ING1 is overexpressed at both mRNA and protein levels in melanoma cell lines compared with normal melanocytes. Single-strand conformation polymorphism (SSCP) analysis showed band shifting in two melanoma cell lines. DNA sequencing confirmed that there were nucleotide alterations in the ING1 gene in Sk-mel-24 and Sk-mel-110 cell lines. Two silent nucleotide alterations in exon 1a were detected in Sk-mel-110. In Sk-mel-24, the A-->G nucleotide alteration at codon 260 resulted in an amino acid change from Asn to Ser, while seven other nucleotide alterations were silent. To determine if the silent nucleotide alterations in these two melanoma cell lines were due to polymorphism, SSCP analysis of ING1 gene was performed in 25 healthy volunteers. No band shift was observed in the SSCP analysis, suggesting that the nucleotide alterations in the melanoma cell lines are unlikely to be due to polymorphism.

CONCLUSIONS

Taken together, our data demonstrate that ING1 is overexpressed, but infrequently mutated, in melanoma cell lines.

The significance of immunohistochemistry in the diagnosis and therapy of neoplasms

This review article details the diagnostical significance of immunohistochemistry, which has developed during the last quarter of the century. Certainly, the advancement of monoclonal antibody technology has been of great significance in assuring the place of immunohistochemistry in the modern accurate microscopic diagnosis of human neoplasms, as a method of choice in histopathology. The fact still remains that in order to properly assess any immunohistochemical reactivity used for differential diagnostic purposes, the target cells have to be identified as neoplastically transformed cells by routine histopathological techniques. Selected groups of target molecules of great significance in cancer biology are discussed. The discovery of neoplasm-associated antigens has not only made the more accurate diagnosis of human cancer feasible but has also shed light on the extensive immunophenotypical heterogeneity of even the most closely linked human malignancies. The identification of disseminated neoplastically transformed cells by immunohistochemistry has allowed for a clearer picture of cancer invasion and metastasis, as well as the evolution of the tumour cell associated immunophenotype towards increased malignancy. Some possibilities of neoplasm-associated antigen targeted, receptor-directed immunotherapy are discussed and reviewed in this manuscript. Future antineoplastic therapeutical approaches should see the inclusion of a variety of immunotherapies, in the form of an individualised 'cocktail' specific for the particular immunophenotypical pattern associated with each individual patient's neoplastic disease.

Prognostic evaluation of cutaneous malignant melanoma: a clinicopathologic and immunohistochemical study

BACKGROUND AND OBJECTIVES

Depth of invasion and stage of the disease are established prognostic indicators in cutaneous malignant melanoma. The role of other parameters is still an open problem.

METHODS

In 93 consecutive patients with cutaneous malignant melanoma, the level of invasion, tumor thickness, ulceration, vascular invasion, lymphoplasmocytic infiltrates, and mitotic index were evaluated by histology. Expression of Ki-67 and PCNA proliferative antigens together with vimentin, S100, and HMB 45 proteins were assessed by immunohistochemistry.

RESULTS AND CONCLUSIONS

Disease-free and overall survival were correlated with tumor stage, tumor thickness, level of invasion, macroscopic pattern, ulceration, vascular invasion, expression of HMB 45, PCNA, and Ki-67/MIB1. Stage, HMB 45, and PCNA were independent prognostic factors for disease-free survival, whereas tumor stage, tumor thickness, and expression of both proliferative antigens influenced overall survival independently. The variables studied demonstrated reciprocal correlation; therefore, analysis of many prognostic parameters in malignant melanoma could be recommended.

p21(WAF1/CIP1) expression in stage I cutaneous malignant melanoma: its relationship with p53, cell proliferation and survival

The expression of p21, p53 and proliferating cell nuclear antigen (PCNA) was analysed by immunohistochemistry in a consecutive series of 369 clinical stage I cutaneous malignant melanoma patients. Correlation of the detected expression levels with each other, with clinicopathological data and with melanoma survival were statistically evaluated. p21 expression was significantly associated with p53 and PCNA expression levels. In addition, high levels of p53 and PCNA were significantly interrelated. Tumour thickness, recurrent disease, high TNM category and older (> or = 55 years) age at diagnosis were inversely associated with p21 expression. Gender, bleeding, tumour thickness, Clark's level of invasion, TNM category and p53 index were all important predictors of both recurrence-free and overall survival of melanoma. In Cox's multivariate analysis including 164 patients with a complete set of data, only high tumour thickness and bleeding predicted poor recurrence-free survival (P = 0.0042 and 0.0087 respectively) or overall survival (P = 0.0147 and 0.0033 respectively). Even though elevated p21 expression may be associated with more favourable prognosis in clinical stage I cutaneous melanoma, our results suggest that cell cycle regulatory effects of p21 can be overcome by some other and stronger, partly yet unknown, mechanisms.

Frequent mutations of the p53 gene in cutaneous melanoma of the nodular type

The frequency and significance of p53 alterations in cutaneous melanoma have not been completely clarified. In the present study, 31 primary melanomas of the nodular type and 15 metastases occurring between 1981 and 1983 were studied with respect to mutations in exons 7 and 8, as well as to p53 protein immunostaining using different antibodies. Altogether 13% of the primary tumors showed strong p53 staining using the DO-7 antibody. Different results were obtained with other antibodies. Seven mutations were found in primary and metastatic tumors; all of these were single base changes, most of which occurred in the core domain of the p53 protein responsible for sequence-specific DNA binding (residues 102-293). The mutations were not significantly associated with p53 staining results, and p53 alterations (mutations or marked immunopositivity) had no prognostic value. Our results indicate that point mutations in exons 7 and 8 are more frequent than previously reported in primary melanomas, and such changes may be important for the development of certain melanoma subgroups.

Prognostic implications of p53 overexpression in cutaneous melanoma from sun-exposed and nonexposed sites

BACKGROUND

There is increasing evidence that mutations in the p53 tumor suppressor gene are among the most common genetic alterations in human malignancies. Because ultraviolet light can induce specific p53 mutations and is linked to the development of skin cancers, this study was done to determine the significance of p53 protein (p53p) overexpression in melanomas originating at different cutaneous sites varying in frequency of sunlight exposure.

METHODS

Sixty-three paraffin embedded primary and metastatic melanoma biopsy specimens from 61 patients were deparaffinized and stained with the mouse monoclonal antibody DO-1 to wild-type and mutant p53p. Twenty-eight specimens were from primary tumors and 35 specimens were from lymph node, subcutaneous, or visceral metastases. The chi-square test was used to assess the significance of p53p overexpression, and the Cox proportional hazards model was used to estimate the impact of p53p overexpression on survival.

RESULTS

Of the 61 patients studied, 37 had primary cutaneous melanomas arising on chronically sun-exposed head and neck sites, 12 patients on intermittently exposed extremity sites, and 12 patients on rarely exposed trunk sites. Thirteen of the 63 primary or metastatic specimens (21%) overexpressed p53p. Overexpression of p53p was not related to patient gender or age, anatomic site of the primary tumor, Clark level, or Breslow thickness. However, those patients with p53p positive primary tumors or metastases had significantly better survival than those determined to be negative for p53p overexpression (P = 0.045). The median survival was 152.4 months for p53p positive patients versus 55.7 months for p53p negative patients. The risk ratio of dying from melanoma was 0.32 for patients with tumor specimens overexpressing p53p.

CONCLUSIONS

In this study, p53p overexpression was infrequent in paraffin embedded melanoma specimens and independent of the primary melanoma's anatomic site. Although p53p overexpression was not related to other prognostic features of primary or metastatic lesions, it was associated with a significantly improved survival in this group of melanoma patients.

Alterations and prognostic significance of p16 and p53 protein expression in subgroups of cutaneous melanoma

The role of p16 and p53 alterations in cutaneous melanoma has been recently discussed, but it remains to be clarified. In the present immunohistochemical study, the expression of p16 and p53 proteins and their possible prognostic relevance have been examined in 102 melanomas of the aggressive nodular type. Twelve percent showed a strong expression of p53 protein, and these cases were significantly more frequent in the head/neck area compared with other sites (32% vs. 6%). Expression of p16 protein was negative or weak in 9% of the cases, and this tended to be less frequent in head/neck tumors compared with the others (0% vs. 12%). Whereas p53 staining was not prognostically important, loss of p16 staining was significantly associated with markedly reduced recurrence free and patient survival in univariate analysis (product-limit method). In multivariate analysis, lack of p16 staining was significantly associated with recurrent disease (p = 0.013). Our findings indicate an important role of altered p16 protein expression in a subgroup of melanoma patients.