p53 immunoreactivity in human malignant melanoma and dysplastic naevi

Germline and Somatic Genetic Variants in the p53 Pathway Interact to Affect Cancer Risk, Progression, and Drug Response

Insights into oncogenesis derived from cancer susceptibility loci (SNP) hold the potential to facilitate better cancer management and treatment through precision oncology. However, therapeutic insights have thus far been limited by our current lack of understanding regarding both interactions of these loci with somatic cancer driver mutations and their influence on tumorigenesis. For example, although both germline and somatic genetic variation to the p53 tumor suppressor pathway are known to promote tumorigenesis, little is known about the extent to which such variants cooperate to alter pathway activity. Here we hypothesize that cancer risk-associated germline variants interact with somatic TP53 mutational status to modify cancer risk, progression, and response to therapy. Focusing on a cancer risk SNP (rs78378222) with a well-documented ability to directly influence p53 activity as well as integration of germline datasets relating to cancer susceptibility with tumor data capturing somatically-acquired genetic variation provided supportive evidence for this hypothesis. Integration of germline and somatic genetic data enabled identification of a novel entry point for therapeutic manipulation of p53 activities. A cluster of cancer risk SNPs resulted in increased expression of prosurvival p53 target gene KITLG and attenuation of p53-mediated responses to genotoxic therapies, which were reversed by pharmacologic inhibition of the prosurvival c-KIT signal. Together, our results offer evidence of how cancer susceptibility SNPs can interact with cancer driver genes to affect cancer progression and identify novel combinatorial therapies. SIGNIFICANCE: These results offer evidence of how cancer susceptibility SNPs can interact with cancer driver genes to affect cancer progression and present novel therapeutic targets.

Expression of Phosphatase and Tensin Homologue, phospho-Akt, and p53 in Acral Benign and Malignant Melanocytic Neoplasms (Benign Nevi, Dysplastic Nevi, and Acral Melanomas)

Background

The role of the phosphatidylinositol-3 kinase signaling pathway in the development of acral melanoma has recently gained evidence. Phosphatase and tensin homologue (PTEN), one of the key molecules in the pathway, acts as a tumor suppressor through either an Akt-dependent or Akt-independent pathway. Akt accelerates degradation of p53.

Objective

We assessed the expression of PTEN, phospho-Akt (p-Akt), and p53 by immunohistochemistry in benign acral nevi, acral dysplastic nevi, and acral melanomas in the radial growth phase and with a vertical growth component.

Methods

Ten specimens in each group were included. Paraffin-embedded specimens were immunostained with antibodies for PTEN, p-Akt, and p53. We scored both the staining intensity and the proportion of positive cells. The final score was calculated by multiplying the intensity score by the proportion score.

Results

All specimens of benign acral nevi except one showed some degree of PTEN-negative cells. The numbers of p-Akt and p53-positive cells were higher in acral dysplastic nevi and melanoma than in benign nevi. P-Akt scores were 1.7, 1.8, 2.6, and 4.4, and p53 scores were 2.0, 2.1, 3.8, and 4.1 in each group. PTEN and p-Akt scores in advanced acral melanoma were higher than in the other neoplasms.

Conclusion

The expression of PTEN was decreased and the expression of p-Akt was increased in acral melanoma, especially in advanced cases. The PTEN-induced pathway appears to affect the late stage of melanomagenesis. Altered expression of p-Akt is thought to be due to secondary changes following the loss of PTEN.

Immunohistologic Evaluation of Putatively Mutant p53 Protein in Cutaneous Melanocytic Neoplasms

Mutations in the p53 tumor suppressor gene, located at chromosomal locus 17pI3, are the most commonly seen genetic alterations found in human malignancies. Their role in the pathogenesis of malignant melanoma is thought to be limited, although variable results have been reported in reference to immunoreactivity for putatively mutant p53 protein (mp53) in melanocytic lesions in general. In that light, the authors undertook an immunohistologic evaluation of 256 well-characterized tumors in that category, including common nevi (CN; n=73); Spitz nevi (SN; n=40); nodular melanomas (NMMs; n=32), superficial spreading melanomas (SMMs; n=65); lentigo maligna melanomas (LMMs; n=23); and melanomas arising in preexisting nevi (MANs; n=23). One hundred cells were counted manually in randomly selected high-power microscopic fields, in regard to nuclear labeling for mp53. Results were recorded semiquantitatively, as negative, positive (1-4% of tumor cells); and positive (>5% of tumor cells). No examples of CN or SN demonstrated any immunoreactivity whatever for mp53, whereas 105 of 143 melanomas (73%) did so. However, an mp53 index of >50% was seen in only 29% of the latter lesions. NMMs were most often mp53-positive and showed the highest numerical level of nuclear labeling, followed in respective order by SMMs, and LMMs/MANs. These results suggest that negative mp53-immunostaining cannot be equated with the diagnostic interpretation of a benign melanocytic neoplasm, because 27% of melanomas also failed to label for that determinant. However, the presence of mp53-immunolabeling in a melanocytic proliferation-even if at low levels-should conversely prompt careful consideration of melanoma as the favored diagnosis in the confined setting of morphologically difficult cases, inasmuch as no example of CN or SN in this series had that characteristic.

p63 is an alternative p53 repressor in melanoma that confers chemoresistance and a poor prognosis

p63 is up-regulated in melanoma and prevents nuclear accumulation of p53.

The role of apoptosis in melanoma pathogenesis and chemoresistance is poorly characterized. Mutations in TP53 occur infrequently, yet the TP53 apoptotic pathway is often abrogated. This may result from alterations in TP53 family members, including the TP53 homologue TP63. Here we demonstrate that TP63 has an antiapoptotic role in melanoma and is responsible for mediating chemoresistance. Although p63 was not expressed in primary melanocytes, up-regulation of p63 mRNA and protein was observed in melanoma cell lines and clinical samples, providing the first evidence of significant p63 expression in this lineage. Upon genotoxic stress, endogenous p63 isoforms were stabilized in both nuclear and mitochondrial subcellular compartments. Our data provide evidence of a physiological interaction between p63 with p53 whereby translocation of p63 to the mitochondria occurred through a codependent process with p53, whereas accumulation of p53 in the nucleus was prevented by p63. Using RNA interference technology, both isoforms of p63 (TA and ΔNp63) were demonstrated to confer chemoresistance, revealing a novel oncogenic role for p63 in melanoma cells. Furthermore, expression of p63 in both primary and metastatic melanoma clinical samples significantly correlated with melanoma-specific deaths in these patients. Ultimately, these observations provide a possible explanation for abrogation of the p53-mediated apoptotic pathway in melanoma, implicating novel approaches aimed at sensitizing melanoma to therapeutic agents.

The dysplastic nevus: from historical perspective to management in the modern era: part II. Molecular aspects and clinical management

The dysplastic nevus is a discreet histologic entity that exhibits some clinical and histologic features overlapping with common nevi and melanoma. These overlapping features present a therapeutic challenge, and with a lack of accepted guidelines, the management of dysplastic nevi remains a controversial subject. Although some differences between dysplastic and common nevi can be detected at the molecular level, there are currently no established markers to predict biologic behavior. In part II of this continuing medical education article, we will review the molecular aspects of dysplastic nevi and their therapeutic implications. Our goal is to provide the clinician with an up-to-date understanding of this entity to facilitate clinical management of patients with nevi that have histologic dysplasia.

Increased expression of MDM2 and NM23 are associated with malignant transformation of pleomorphic adenoma

This study was designed to correlate the expression of both MDM2 and NM23 in pleomorphic adenoma (PA) to clinical background, histological features, local recurrence, and metastatic potentiality in this tumor. Expression of MDM2 and NM23 was studied immunohistochemically in 23 cases of PA. Our results demonstrated MDM2 and NM23 overexpression in almost all cases of PA. There was a significant difference of the MDM2 and NM23 mean values between benign PA and both carcinoma-ex PA and metastasizing PA. The results of this study show that the overexpression of NM23 and MDM2 oncoproteins could be used as reliable predictors of malignant progression as well as metastatic potentiality of PA.

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.

BRAF(E600) in benign and malignant human tumours

Of the RAF family of protein kinases, BRAF is the only member to be frequently activated by mutation in cancer. A single amino acid substitution (V600E) accounts for the vast majority and results in constitutive activation of BRAF kinase function. Its expression is required to maintain the proliferative and oncogenic characteristics of BRAF(E600)-expressing human tumour cells. Although BRAF(E600) acts as an oncogene in the context of additional genetic lesions, in primary cells it appears to be associated rather with transient stimulation of proliferation. Eventually, BRAF(E600) signalling triggers cell cycle arrest with the hallmarks of cellular senescence, as is illustrated by several recent studies in cultured cells, animal models and benign human lesions. In this review, we will discuss recent advances in our understanding of the role of BRAF(E600) in benign and malignant human tumours and the implications for therapeutic intervention.

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.

Therapy of established B16-F10 melanoma tumors by a single vaccination of CTL/T helper peptides in VacciMax

BACKGROUND

Melanoma tumors are known to express antigens that usually induce weak immune responses of short duration. Expression of both tumor-associated antigens p53 and TRP2 by melanoma cells raises the possibility of simultaneously targeting more than one antigen in a therapeutic vaccine. In this report, we show that VacciMax (VM), a novel liposome-based vaccine delivery platform, can increase the immunogenicity of melanoma associated antigens, resulting in tumor elimination.

METHODS

C57BL/6 mice bearing B16-F10 melanoma tumors were vaccinated subcutaneously 6 days post tumor implantation with a mixture of synthetic peptides (modified p53: 232-240, TRP-2: 181-188 and PADRE) and CpG. Tumor growth was monitored and antigen-specific splenocyte responses were assayed by ELISPOT.

RESULTS

Vaccine formulated in VM increased the number of both TRP2- and p53-specific IFN-gamma producing splenocytes following a single vaccination. Vaccine formulated without VM resulted only in enhanced IFN-gamma producing splenocytes to one CTL epitopes (TRP2:180-188), suggesting that VM overcomes antigen dominance and enhances immunogenicity of multiple epitopes. Vaccination of mice bearing 6-day old B16-F10 tumors with both TRP2 and p53-peptides formulated in VM successfully eradicated tumors in all mice. A control vaccine which contained all ingredients except liposomes resulted in eradication of tumors in no more than 20% of mice.

CONCLUSION

A single administration of VM is capable of inducing an effective CTL response to multiple tumor-associated antigens. The responses generated were able to reject 6-day old B16-F10 tumors.

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.

p53 plays a central role in UVA and UVB induced cell damage and apoptosis in melanoma cells

We investigated whether p53 plays a role in UV induced apoptosis in melanoma. UVA and UVB induced apoptosis in dose dependent and wild type p53 melanoma cells were much more vulnerable than the mutant cells, indicating that p53 played a role in UV-induced apoptosis in melanoma. No difference in p53 expression pattern between the primary and matched metastatic melanomas was noticed in tumour tissue or cell lines from the same patients. Our findings indicate that expression of p53 plays a role in UV-induced apoptosis in melanoma cells, but not important in melanoma progression from primary to metastasis.

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.

The effects of gp100 and tyrosinase peptide vaccinations on nevi in melanoma patients

BACKGROUND

A new approach to prevent disease recurrence in high-risk melanoma patients involves immunization with gp100 and tyrosinase peptides. This is the first study to examine the effects of such treatments on nevi.

DESIGN

We studied biopsies of 'clinically atypical' nevi from 10 patients before and after peptide vaccination. All had a cutaneous melanoma measuring at least 1.5 mm in depth, satellite metastases, or at least one positive lymph node. We performed immunohistochemical stains for CD3, CD4, CD8, MHC-I, MHC-II, CD1a, HMB-45, MART-1, tyrosinase, bcl-2, p53, and Ki-67 (mib-1).

RESULTS

Immunohistochemistry showed no differences in staining due to vaccination in either the immunologic or melanocytic markers. However, there was a significant increase in both p53 and bcl-2 staining, and a trend toward decreased Ki-67 staining, in the nevi post-treatment.

DISCUSSION

The primary goal of peptide vaccinations with gp100 and tyrosinase is to activate melanoma-specific T cells in order to prevent melanoma recurrence. Nevi were studied in order to assess the effects on benign melanocytes. No significant changes in lymphocytes, langerhans cells, expression of MHC antigens, or melanocytic markers were found. The increase in p53 and bcl-2 raises the possibility that vaccination with melanocytic antigens stimulates a response in benign melanocytes.

Cellular UV damage responses--functions of tumor suppressor p53

DNA damage, provoked by ultraviolet (UV) radiation, evokes a cellular damage response composed of activation of stress signaling and DNA checkpoint functions. These are translated to responses of replicative arrest, damage repair, and apoptosis aimed at cellular recovery from the damage. p53 tumor suppressor is a central stress response protein, activated by multiple endogenous and environmental insults, including UV radiation. The significance of p53 in the DNA damage responses has frequently been reviewed in the context of ionizing radiation or other double strand break (DSB)-inducing agents. Despite partly similar patterns, the molecular events following UV radiation are, however, distinct from the responses induced by DSBs and are profoundly coupled with transcriptional stress. These are illustrated, e.g., by the UV damage-specific translocations of Mdm2, promyelocytic leukemia protein, and nucleophosmin and their interactions with p53. In this review, we discuss UV damage-provoked cellular responses and the functions of p53 in damage recovery and cell death.

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.

Ki-67 and p53 expression in minimal deviation melanomas as compared with other nevomelanocytic lesions

Minimal deviation melanoma is a controversial entity encompassing a heterogeneous group of lesions cytologically in the spectrum between recognized subtypes of nevi and conventional "primary configuration" melanomas and reported to have a better prognosis than the latter. To evaluate the distinctiveness of minimal deviation melanoma, Ki-67 proliferation rates and p53 expression in minimal deviation melanomas were compared with those in compound nevi, Spitz nevi, and vertical growth phase superficial spreading malignant melanoma. Twelve examples of each lesion were immunostained with antibodies to the Ki-67 and p53 proteins and evaluated by a pathologist who was blind to the diagnoses. The mean Ki-67 (MIB-1) proliferation rates for the compound nevi, Spitz nevi, minimal deviation melanomas, and superficial spreading malignant melanomas were 0, 3%, 13%, and 25%, respectively. The mean Ki-67 proliferation rate was statistically greater in the minimal deviation melanomas than in the compound nevi or the Spitz nevi (P <.05), but the proliferation rates in the two melanoma subtypes were not statistically significant (P =.08). The mean p53 values for these lesions were 0, 9%, 9%, and 26%, respectively; the latter two were statistically different (P <.01). Based on these Ki-67 and p53 immunophenotypes, minimal deviation melanoma may represent a distinct entity.

Molecular aspects of melanocytic dysplastic nevi

Melanocytic dysplastic nevi were first described in both patients and their relatives who had one or several cutaneous malignant melanomas. Most of these dysplastic lesions are biologically stable, but some of them have severe histological atypia and can progress further to melanomas. Although several studies have suggested the etiological importance of dysplastic nevi in the development of melanomas, comprehensive reviews of the molecular changes in these dysplastic lesions are still scarce. To remedy this issue, this article analyzes the available molecular information about dysplastic nevi and provides the current state of knowledge regarding the karyotypic abnormalities of the melanoma/dysplastic nevus trait and the involvement of allelic loss, tumor suppressor genes, mismatch repair proteins, microsatellite instability, oncogenes, extracellular matrix proteins, and growth factors in the genesis of these lesions. These studies suggest that although some of these lesions represent "genetic dead-ends," others represent intermediate lesional steps in the melanoma tumorigenesis pathway.

nm23-H1 protein immunoreactivity in intraepithelial neoplasia and invasive squamous cell carcinoma of the uterine cervix

Differences in the immunohistochemical expression of the 17 kDa protein encoded by the human nm23-H1 gene were studied in premalignant lesions and invasive squamous cell carcinoma (SCC) (N = 8) of the cervix using routine streptavidin-biotin immunohistochemistry and a polyclonal antibody to the nm23-H1 protein. The premalignant lesions were koilocytic atypia due to wart virus infection (N = 5), low-grade cervical intraepithelial neoplasia (CIN) (N = 7) and high-grade CIN (N = 7). The carcinomas were either moderately (N = 3) or poorly differentiated (N = 5). The non-neoplastic controls were normal squamous epithelium from cases with uterine prolapse (N = 7) and normal squamous epithelium not affected by the infective or neoplastic areas of some of the cases with wart virus infection (N = 2) and carcinoma (N = 2). Moderate to strong cytoplasmic and, occasionally, nuclear immunostaining for the nm23-H1 protein was seen in all cells above the basal layer of the normal squamous epithelium. However, most of the cervical SCC show a relative reduction in nm23-H1 immunoreactivity (7/8 cases; 88%). This difference in nm23-H1 expression was statistically significant (P = 0.0006; Chi-squared test with continuity correction). All of the cases with wart virus infection (N = 5; 100%) displayed moderately strong nm23-H1 immunostaining throughout the squamous epithelium except for the basal layer where no staining was observed. The cases that had low-grade squamous dysplasia of the cervix (CIN I-II) (N = 7; 100%) also displayed moderate to strong nm23-H1 immunoreactivity in the epithelium except for the basal layer (CIN I) or the lower two-thirds of the epithelium (CIN II). nm23-H1 Immunoreactivity was either absent or was significantly reduced in all of the high-grade CIN (CIN III) cases (N = 7; 100%) in which only the non-dysplastic superficial third of the squamous epithelium displayed nm23-H1 immunolabeling. The difference in nm23-H1 expression between low-grade and high-grade CIN cases was statistically significant (P = 0.0013; Chi-squared test with continuity correction). Similarly, the difference between low-grade CIN and SCC cases in the expression of nm23-H1 was also significant (P = 0.0041; Chi-squared test with continuity correction). However, no statistically significant difference in nm23-H1 immunoreactivity was found between cases of high-grade CIN and SCC. In conclusion, nm23-H1 protein immunoreactivity is reduced in high-grade CIN and cervical SCC but not in low-grade CIN. These findings suggest that reduced expression of the protein may be important early in the sequential development of cervical squamous neoplasia.

p53 expression and risk factors for cutaneous melanoma: a case-control study

Epidemiological data strongly implicate sunlight as the principal environmental cause of melanoma; however, critical molecular targets for ultraviolet (UV)-induced melanoma remain to be identified. The p53 tumor suppressor gene is one possible target, being abnormally expressed in 20-40% of primary melanomas. We undertook a population-based molecular epidemiological study with the aim of determining the environmental and phenotypic factors associated with p53-positive and p53-negative melanomas. One hundred fifty cases of melanoma were randomly ascertained from the Queensland Cancer Registry and matched to 150 electoral roll controls. Data on environmental and phenotypic exposures were collected through interviews and physical examination of all participants. Sections of tumor tissue were obtained from 134 (89%) cases and stained with the anti-p53 DO-7 monoclonal antibody (MAb) following microwave antigen retrieval. Of 121 useable sections, 22 tumors (18%) had more than 1% cells with positive staining consistent with abnormalities in p53 expression. Strongest predictors of p53-positive melanoma were inability to tan [odds ratio (OR) 6.8], history of non-melanoma skin cancer (OR 3.2) and site of melanoma: head/neck (OR 2.2) and lower limbs (OR 2.3). In contrast, factors such as nevus density and freckling propensity were strongly associated only with p53-immunonegative melanoma (OR 8.6 for >25 moles; OR 3.0 for heavy facial freckling). Overall, the determinants of p53-positive and p53-negative melanomas were independent and complementary, the former being associated with features of sun-sensitivity and chronic sun exposure, the latter with phenotypic markers of melanocytic proliferation. Our findings are consistent with at least 2 independent pathways in the pathogenesis of melanoma, characterized by environmental induction and p53 overexpression on the one hand and pigment cell instability on the other.

p53 protein immunoreactivity in fibrohistiocytic tumors of the skin

Abnormal expression of the 53 kDa nuclear phosphoprotein produced by the p53 gene is observed in many human cancers. p53 nuclear immunoreactivity is found commonly in tumor cells. Immunohistochemistry was performed using a monoclonal antibody, DO-7 (DAKO, Denmark; cat. no. M7001; 1:100 dilution), to investigate p53 protein immunoreactivity in a group of cutaneous fibrohistiocytic tumors that are known to be locally aggressive. The study group consisted of dermatofibrosarcoma protuberans (DFSP) (n = 14) and atypical fibroxanthoma (AFX) (n = 7). Cases of dermatofibroma (DF) (n = 16) formed the benign control group. Intense nuclear immunostaining for p53 protein was observed in 71% of DFSP and 86% of AFX. None of the dermatofibromas showed strong p53 nuclear immunostaining. Statistical analyses revealed significant differences in p53 immunoreactivity between DFSP and DF (P = 0.0001, chi 2 test) and between AFX and DF (P = 0.0001, chi 2 test). In conclusion, increased p53 protein immunoreactivity is found in DFSP and AFX but not in DF. These differences in p53 immunoreactivity suggest that increased expression of the protein may be important in the pathogenesis of the more aggressive group of fibrohistiocytic tumors.

Molecular and cellular effects of ultraviolet light-induced genotoxicity

Exposure to the solar ultraviolet spectrum that penetrates the Earth's stratosphere (UVA and UVB) causes cellular DNA damage within skin cells. This damage is elicited directly through absorption of energy (UVB), and indirectly through intermediates such as sensitizer radicals and reactive oxygen species (UVA). DNA damage is detected as strand breaks or as base lesions, the most common lesions being 8-hydroxydeoxyguanosine (8OHdG) from UVA exposure and cyclobutane pyrimidine dimers from UVB exposure. The presence of these products in the genome may cause misreading and misreplication. Cells are protected by free radical scavengers that remove potentially mutagenic radical intermediates. In addition, the glutathione-S-transferase family can catalyze the removal of epoxides and peroxides. An extensive repair capacity exists for removing (1) strand breaks, (2) small base modifications (8OHdG), and (3) bulky lesions (cyclobutane pyrimidine dimers). UV also stimulates the cell to produce early response genes that activate a cascade of signaling molecules (e.g., protein kinases) and protective enzymes (e.g., haem oxygenase). The cell cycle is restricted via p53-dependent and -independent pathways to facilitate repair processes prior to replication and division. Failure to rescue the cell from replication block will ultimately lead to cell death, and apoptosis may be induced. The implications for UV-induced genotoxicity in disease are considered.

A review of tumor suppressor genes in cutaneous neoplasms with emphasis on cell cycle regulators

Cells normally have five options. These include renewal or proliferation, terminal differentiation, quiescence, senescence, and apoptosis. Many factors interact with cell cycle regulators to direct the cells toward these different options. Tumor suppressor genes play a pivotal role in this process. Alterations in these genes may limit the options that cells have and thus play a significant role in the multistep process of carcinogenesis. We will focus on tumor suppressor genes and especially tumor suppressor genes that interact directly with the cell cycle proteins.

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.

Differential expression of metallopanstimulin/S27 ribosomal protein in melanocytic lesions of the skin

We have previously shown that human metallopanstimulin (MPS-1) is a ubiquitous 9.4-kDa multifunctional ribosomal S27/nuclear "zinc finger" protein which is expressed at high levels in a wide variety of cultured proliferating cells and tumor tissues, including melanoma. In the present study, we have examined the expression of the MPS-1 protein in various types of human benign and malignant melanocytic lesions of the skin. The expression of the MPS-1 protein was studied by immunohistochemistry using specific anti-MPS-1 antibodies. We found that in benign nevi, the staining is weak and in a gradient; most often, only type A melanocytes stain positive. The B and particularly the C types are negative. Remarkably, congenital nevi show a similar gradient staining of regular benign nevi, but in addition one example showed intensely positive dermal nodules adjacent to areas of negative melanocytes. In melanomas, the staining patterns for MPS-1 are more complex. While some melanomas stain evenly and intensely positive, others have remarkably variable expression of MPS-1. The scattered melanocytes migrating to the upper layers of the epidermis are usually intensely positive. In summary, benign lesions stain in an orderly pattern with staining gradients that correlate with the cellular differentiation of the nevi. Malignant melanomas have an erratic, often intense staining that also correlates with the disorderly growth of these neoplasms. These differential results indicate that the MPS-1 antigen is a useful marker for melanocytic lesions at the immunohistochemical level.

One single erythemagenic UV irradiation is more effective in increasing the proliferative activity of melanocytes in melanocytic naevi compared with fractionally applied high doses

The effect of a single irradiation with UV light on the expression of Ki67 antigen, topoisomerase II alpha, proliferating cell nuclear antigen (PCNA), the melanocyte activation marker HMB-45 and protein p53 in melanocytic naevi was investigated 1 week after application of a single erythemagenic UV dose and after daily exposures with suberythemagenic doses over 4-6 weeks. To assess the effect of UV irradiation, one half of each naevus was shielded with black tape during the UV exposure, and the irradiated part and the non-irradiated parts were evaluated separately. Except for HMB-45, a double staining procedure was performed to distinguish between labelled melanocytes and keratinocytes. After semiquantitative assessment of the staining signal the irradiated part was compared with the non-irradiated part of the same naevus. Morphological changes and an enhanced proliferative/ reparative activity in melanocytes were much more frequent in the naevi irradiated with a single erythemagenic UV dose than in those given repeated suberythemagenic doses. In addition, the keratinocytes showed an increased labelling for PCNA and p53 after the single irradiation. These data may support the importance of intermittent UV exposure and sunburns in the development of both benign and malignant melanocytic lesions.

Cutaneous melanoma in patients with sarcoma

BACKGROUND

The authors became interested in an association between cutaneous melanoma and sarcoma when they reviewed their experience with other malignancies occurring in patients with a diagnosis of sarcoma.

METHODS

The authors identified 48 patients with both melanoma and bone or soft tissue sarcoma (STS) by a computer search of all sarcoma patients entered into their institution's cancer registry between 1943 and 1996 who had an additional diagnosis of melanoma. The medical records were reviewed and clinical and pathologic data collected.

RESULTS

The median age at diagnosis was 46 years for patients with melanoma and 50 years for patients with sarcoma, which was consistent with population-based data. Among patients with STS (n = 41), malignant peripheral nerve sheath tumors (MPNT) were more common in patients with both diagnoses (5 of 41; 13%) when compared with all adults with STS admitted to the study center between 1982 to date (125 of 2901; 4%; P < 0.05). Liposarcoma occurred in only 1 patient with both melanoma and STS (1 of 41; 2%), despite the fact that it was the most common histologic diagnosis in all adults with STS (625 of 2901; 22%; P < 0.001). The anatomic site of STS was more commonly visceral (11 of 41; 27%) when compared with all adults with STS (424 of 2901; 15%; P < 0.05). A positive family history of cancer was noted in 50% of the patients, and 25% of patients had a third primary tumor.

CONCLUSIONS

Although a distinct "melanoma/sarcoma" syndrome was not identified, MPNT as well as visceral sarcomas were more common than expected in this study. The authors also noted strong family histories of cancer as well as additional primary malignancies in patients with melanoma and sarcoma, suggesting a predisposition toward cancer.

p53 expression in uveal malignant melanomas

Mutation of the p53 gene which is located on chromosome 17p is the single most frequent alteration observed in human cancer. In this study we evaluate malignant melanoma, the most common intraocular neoplasm in adults, for aberrant p53 expression. Twenty enucleation specimens representing one ciliary body and 17 choroidal melanomas and two choroidal nevi were studied by immunohistochemistry utilizing the D07 anti-p53 antibody and the MIB-1 monoclonal antibody. The tumors included two spindle cell and 16 mixed cell (spindle + epithelioid cell) melanomas and two spindle cell nevi. The MIB-1 labelling index ranged from < 1% (two cases), 1-5% (13 cases) and > 5% (five cases). Of the 18 melanomas, 13 cases showed nuclear p53 staining with the p53 index < 1% (two cases), 1-3% (eight cases) and 4-5% (three cases). No p53 staining was observed in two malignant melanomas of the spindle cell type and in two choroidal nevi. In the 13 malignant melanomas of the mixed cell type, there was no correlation between MIB-1 index and p53 immunoreactivity. Immunopositivity was not found in normal choroidal melanocytes. Our study suggests that p53 alterations may be found in uveal melanomas; in our series, p53 positivity was present only in malignant melanomas of the mixed cell type.

An immunohistochemical study of p53 protein expression in classical Kaposi's sarcoma

The present study was performed to determine the frequency of p53 protein immunoreactivity in classical Kaposi's sarcoma (KS) as a whole and in relation to the histological subtypes which are considered to correspond to the developmental stages of the tumor. The accumulation of p53 protein was studied immunohistochemically using monoclonal antibody BP53-12 on formalin-fixed paraffin-embedded sections of 36 KS lesions, of which 14 were classified histologically as early type and 22 as spindle-cell or mixed type. No positive immunoreactivity was detected in any of the 14 early-type lesions. Among the 22 spindle-cell and mixed variants, positive staining was detected in 5-10% of the tumor cells in one lesion, 1-5% of the cells in six lesions, and in < 1% of the cells in two lesions. These very small percentages of positively stained cells in less than half of the cases of the spindle-cell and mixed variants do not support a significant role for p53 in tumor progression and evolution in KS.

Immunohistochemical expression of p53 protein, mitotic index and nuclear morphometry in primary malignant melanoma of the skin

The immunohistochemical expression of the p53 tumor suppressor protein and the nuclear morphometric parameters were studied in 80 primary skin melanomas. The mitotic index was counted in 64 tumors. In 95% of the tumors p53 positive nuclei were detected, but in only 31% of the cases was the proportion of positive nuclei 3% or higher. The mitotic indices and the mean nuclear areas were not significantly different in melanomas with different p53 expression levels. The p53 positive nuclei had a larger mean nuclear area than the p53 negative nuclei. p53 expression did not increase with melanoma thickness. In Cox's stepwise proportional hazards model, the ratio of mean nuclear long and short axis and melanoma thickness had independent prognostic value, while the level of p53 expression, the mitotic index, and the mean nuclear area were not significantly associated with survival. We conclude that the nuclei expressing p53 protein are larger than p53 negative nuclei. The level of immunohistochemical expression of p53 is low in primary skin melanoma, and it is not valuable as a general prognostic marker for this tumor. p53 expression is not associated with melanoma thickness, indicating that high p53 expression is not a late phenomenon in the progression of this tumor.

Overexpression and mutations of p53 in metastatic malignant melanomas

Alterations of the p53 tumor suppressor gene are the most frequent genetic abnormalities in human malignancies, but the role of p53 in the etiology of malignant melanomas is unclear. Fifty unselected malignant melanomas were analyzed for p53 overexpression by immunohistochemistry using 3 monoclonal antibodies (MAbs). Fifteen tumors (29.4%) showed positive staining with at least 2 different antibodies. In the first 20 consecutive tumors exons 5-9 and adjacent splice sites of the p53 gene were analyzed by genomic sequencing. There were 4 mutations in 20 metastatic melanomas. Three of 4 mutations were C:G-->T:A transitions. A search of our database of p53 mutations revealed that out of 8 p53 mutations reported by others, 4 are C:G-->T:A transitions at dipyrimidine sites, and one is a tandem CC-->TT mutation. This mutational pattern is comparable with the pattern of p53 mutations in squamous cell and basal cell carcinomas of the skin and is related to exposure to ultraviolet B (UV-B) wavelength radiation. Taken together with a predominance of UV-induced mutations in the CDKN2/ p16 gene demonstrated in melanoma cell lines, our data support a role of sunlight exposure in the etiology of malignant melanoma. The low frequency of p53 mutants in melanomas compared with other types of skin cancers suggests that although mutations in this gene are likely to be involved in the development of some malignant melanomas, they do not play as large a role as in squamous and basal cell carcinomas of the skin.

Expression of p53 protein in melanoma progression

p53, A tumor suppressor gene, has been documented as the most frequently mutated gene in human cancers including non-melanoma skin tumors. It has been controversial whether the p53 gene mutation plays a major role for melanoma genesis. To examine the role of p53 in human malignant melanoma carcinogenesis, we performed immunohistochemical analysis using anti-p53 antibodies (CM-1 and DO-7) in microwaved paraffin sections. When cases having more than 1% reactive cells were regarded as positive, immunohistochemical analysis revealed that in primary melanomas 14 of 51 (27%) were positive with CM-1 or 15 of 51 (29%) were positive with DO-7. Tumor thickness of primary melanomas in p53 positive cases was significantly thicker than that in p53 negative cases. In metastatic melanomas, 35 of 41 (85%) lymph node metastases were positive with either antibody and in skin metastases 16 of 28 (57%) lesions with CM-1 or 18 of 28 (64%) lesions with DO-7 were positive. The mean percentages of reactive cells were 2.3% in primary lesions and 4.9% in metastases. The incidence of positivity was significantly higher in metastases than primary lesions. In 10 cases examined, with both primary and metastatic melanoma, 3 cases were negative in both lesions and 1 case was positive in both lesions, while 6 cases were negative in the primary lesions and positive only in metastatic lesions. Four Spitz nevi, 6 dysplastic nevi and 11 common nevi were all negative. These data suggest that the expression of p53 protein may be a late event in melanoma progression.

nm23-H1 protein immunoreactivity in laryngeal carcinoma

BACKGROUND

The nm23-H1 gene encodes a 17-kilodalton cytoplasmic and nuclear protein that has recently been shown to be reduced in a number of human carcinomas including breast, colorectal, lung, gallbladder, and biliary tract carcinomas. This study examines the immunohistochemical staining characteristics of the nm23-H1 protein in human laryngeal carcinomas and nonneoplastic laryngeal polyps, and attempts to determine if there is any relationship between reduction of nm23-H1 protein immunoreactivity and prognosis of patients with laryngeal carcinoma.

METHODS

Routine streptavidin-biotin immunohistochemistry with a polyclonal antibody was employed to study the expression of the nm23-H1 protein in laryngeal squamous cell carcinoma (SCC) (N = 22) and nonneoplastic polyps (N = 8). The carcinomas were classified as well differentiated (N = 2), moderately differentiated (N =15), and poorly differentiated (N = 5). Tissues from metastatic tumor deposits in lymph nodes (N = 5) were also studied. A semiquantitative immunostaining index was derived from the intensity and extent of staining of the cells.

RESULTS

All laryngeal polyps showed intense immunostaining for the nm23-H1 gene product in the squamous epithelium. However, reduced immunoreactivity was found in nearly half of the SCC cases (N = 10; 46%), with the least staining intensity found in tumor metastases in lymph nodes (N = 4; 80%), and were associated with a shorter median survival of 14.3 months. In contrast, tumors that demonstrated moderate to strong nm23-H1 protein immunostaining were associated with a longer median survival period of 20.4 months.

CONCLUSIONS

There is reduced expression of the nm23-H1 gene in human laryngeal SCC compared with nonneoplastic laryngeal polyps. Reduction in the intensity and extent of nm23-H1 protein immunostaining appears to correspond to reduced duration of patients survival.

Cell growth and p53 expression in primary acquired melanosis and conjunctival melanoma

AIMS

To evaluate cell growth and the pattern of p53 suppressor gene expression in atypical primary acquired melanosis (PAM) and in recurrent conjunctival melanoma.

METHODS

Eighteen specimens of PAM with atypia and 24 specimens, comprising early and late lesions, from 12 patients with conjunctival melanoma were stained for the proliferating cell nuclear antigen using the PC10 antibody, and for the p53 gene product using the BP53-12-1, 1801 and DO7 clones. The immunoreactive cells were counted manually and the data evaluated statistically.

RESULTS

Seven of nine PAM specimens progressing to melanoma expressed PC10. None of these lesions expressed the p53 gene product. The number of proliferating cells was higher in the late than in the early lesions of conjunctival melanoma. Four of the 12 recurrent melanomas displayed focal, but minimal, p53 expression. The proliferating cell count in the p53 positive tumours was very similar to that of the p53 negative conjunctival melanomas.

CONCLUSION

Examination of the expression of proliferating cells in atypical PAM may be used as an adjunct to predict which lesions will progress to melanoma. The increase in the number of proliferating cells over time in recurrent conjunctival melanomas probably reflects more aggressive behaviour and may be used to monitor recurrence. The absence of p53 expression in PAM and minimal staining of conjunctival melanomas did not correlate with cell growth, suggesting that alterations in the p53 tumour suppressor gene are uncommon and late events in conjunctival melanoma, and that p53 expression is unlikely to be a useful prognostic indicator.

Predominance of the metastatic phenotype in hybrids formed by fusion of mouse and human melanoma clones

The fusion of mouse and human melanoma cells that were tumorigenic but had different metastatic capabilities resulted in hybrids that were metastatic when injected intravenously or subcutaneously into nude mice, regardless of whether it was the mouse or the human melanoma clone that was metastatic. The H7 hybrid line, formed by fusing murine nonmetastatic K1735 C19 cells with human metastatic A375 C15 cells retained high metastatic potential over more than 50 sub-culture passages, suggesting that the dominant metastatic phenotype in these hybrid cells was stable. Using fluorescent in situ hybridization (FISH), human chromosome 17 was consistently identified as the predominant human chromosome in the majority of H7 cells tested between passages 20 and 60. Western blot analysis showed that the hybrid cells expressed human nm23 protein, indicating that at least one gene on the human chromosome 17 was functional. Immunocytochemistry and immunoprecipitation showed that the metastatic A375 C15 and H7 cells expressed p53 protein, but that the nonmetastatic K1735 C19 melanoma cells did not. Sequencing the human p53 gene in A375 C15N and H7 showed mutations in exon 7. Using a bioassay technique, we showed that K1735 C19 cells can spread from subcutaneous tumors to the lungs of nude mice yet fail to form metastases. With the addition of human chromosome 17 from A375 C15 cells, which carries a mutant p53 gene, the cells readily formed lung metastases. In this melanoma hybrid, a mutant p53 gene appears to confer a survival advantage on cells arrested in the lungs of nude mice and thus contributes to the growth of metastatic cells.

p53 in cutaneous melanoma: immunoreactivity and correlation with prognosis

p53 protein immunoreactivity was investigated in cutaneous Spitz naevi (n = 7), superficial spreading (n = 21) and nodular (n = 6) melanomas using the monoclonal antibody DO-7. Nuclear immunostaining for p53 protein was observed in 41% of all the melanomas but not in any of the Spitz naevi studied. This difference in p53 immunoreactivity appeared statistically significant (P = 0.0001; chi 2 test). There were also differences in p53 immunoreactivity between superficial spreading and nodular melanomas (P = 0.001, chi 2 test), where up to 38% of superficial spreading melanomas and 50% of nodular melanomas had demonstrated p53 nuclear immunostaining. An apparently significant correlation was observed between melanomas with poor prognostic histological indices and p53 immunoreactivity (P = 0.0016; chi 2 test). In conclusion, increased p53 protein immunoreactivity is found in melanomas and is associated with poorer prognosis. The differences in p53 immunohistological expression between cutaneous melanomas and Spitz naevi suggest that alterations of the protein may be important in the pathogenesis of the tumour.

Prognostic indicators in a range of astrocytic tumours: an immunohistochemical study with Ki-67 and p53 antibodies

The treatment and prognosis of patients with cerebral astrocytic tumours are currently guided by histopathological classification. This study evaluates immunohistochemistry using Ki-67, an antibody to a nuclear protein expressed in proliferating cells, and DO-7, an antibody to the product of the tumour suppressor gene p53, as prognostic indicators for these tumours. Immunohistochemistry with Ki-67 has been correlated with the behaviour of many different tumours, but its value as a prognostic indicator in astrocytic tumours is diminished by the conflicting results of previous studies. Immunohistochemistry with antibodies to the p53 protein has been used as a prognostic indicator in melanomas and some carcinomas, but the relation between prognosis and accumulation of this protein in astrocytic tumours has not been clarified. We have tested the hypothesis that survival is correlated with Ki-67 immunolabelling indices (LIs) and patterns of p53 immunolabelling in the cerebral astrocytic tumours of a large cohort of patients (n = 123) for whom clinical indices were well documented. Astrocytic tumours were divided into three histological types: fibrillary astrocytoma (n = 24), anaplastic astrocytoma (n = 31), and glioblastoma (n = 68). Histological type and patient age were independent predictors of survival. Median Ki-67 LIs differed significantly (P < 0.0001) between the types of astrocytic tumour, and tumours with a Ki-67 LI < 2% had a significantly (P < 0.0001) better prognosis. Ki-67 LI as a continuous variable carried a significant (P = 0.0043) unadjusted hazard to survival which was lost when adjusted for other variables, notably histological type. By contrast, no relation was found between survival and three categories of p53 labeling (p53-negative, p53 LI < 40%, and p53 LI > 60%). The results indicate that, whereas Ki-67 immunohistochemistry predicts survival in patients with astrocytic tumours, conventional histological appraisal remains the best guide to prognosis, and immunohistochemistry for p53 has no value in the assessment of these tumours.

Expression of p53 protein in malignant melanoma: clinicopathological and prognostic implications

In the present study, we investigated the expression of the tumour suppressor protein p53 in 113 primary and 43 metastatic malignant melanomas by immunohistochemistry, and correlated the findings with clinicopathological parameters such as histological melanoma subtype, thickness of primary melanomas (Breslow thickness) and patient outcome. In primary melanomas, the polyclonal anti-p53 antibody CM-1 detected immunoreactivity in 70% of the lesions, predominantly in the cytoplasm. Signals were observed in this cellular compartment in 57% of the melanomas, whereas in 32% nuclear p53 over-expression was detected. Immunohistochemistry, using the monoclonal antibody DO-1, revealed lower staining frequencies. However, both antibodies showed congruent results in approximately 80% of the cases. Overall, immunoreactivity was observed in 73% of superficial spreading melanomas, but only in 52% of lentigo maligna melanomas. This difference (P < 0.001) was mainly due to a lower frequency of cytoplasmic immunoreactivity (P < 0.002). There was no difference with respect to cytoplasmic and nuclear immunoreactivity between thin (< 1 mm thickness) and thicker primary melanomas. Staining frequencies detected in metastatic lesions seemed to be lower than in primary tumours. In 103 primary melanomas, follow-up data for at least 5 years were available. In 71% (54 of 76) of the primary melanomas which did not recur, and in 78% (21 of 27) of tumours with subsequent metastases, p53 over-expression was detected by CM-1. However, this difference was not statistically significant. The results of the present study indicate that immunoreactivity to anti-p53 antibodies is a common observation in malignant melanomas, with staining signals predominantly found in the cytoplasm of cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell proliferation markers in predicting metastases in malignant melanoma

It is often difficult to predict the outcome of melanoma in patients with Clark level III-IV disease. We sought to identify markers of cell proliferation which may be useful in predicting prognosis. Patients with Clark's level III-IV malignant melanoma who had no local recurrences or metastases were matched with patients of comparable level and thickness who did experience recurrences of metastases. Cell proliferation markers p53, proliferating cell nuclear antigen (PCNA), and Ki-67 were assessed by immunohistochemistry. DNA ploidy was determined by flow cytometry. There was no difference in the expression of p53, PCNA, and Ki-67 between patients with metastases and patients without metastases. However, patients with metastases were more likely to have an aneuploid tumor cell population than were patients without metastases (p < 0.03). Expression of cell proliferation markers do not appear to help predict prognosis in advanced level melanoma; however, aneuploidy may be associated with a greater probability of metastasis.

Proto-oncogenes and oncogenes in epidermal neoplasia

This review briefly will focus on the role of selected proto-oncogenes and their activated forms during the regulation of cell proliferation, cell death and tumor formation in the epidermis. In addition, the multiple and complex functions of these proteins in normal as well as transformed cells will be discussed.

Expression of the p53 protein in malignant melanomas as a prognostic indicator

It is currently widely accepted that the tumour suppressor gene p53 is critically involved in the proliferation and differentiation of tumour cells including melanoma cells. In the present study, we examined 60 cases of primary melanoma to compare the expression of p53 protein with conventional prognostic markers for melanoma such as clinical and histological parameters. No correlation was found between the p53 protein and clinical factors except for the presence of a metastatic node and development to clinical stage II. However, the expression of p53 protein was significantly associated with tumour thickness over 1.5 mm, levels IV and V of invasion, the presence of ulceration, and high mitotic rate for 5-year survival rate. Although many questions still remain to be answered, our results and those of others for various other malignant tumours, implicate p53 in malignant transformation of pigment cells. Indeed, it could be a new marker for an unfavourable prognosis of malignant melanoma, even though the gene mutation in this highly lethal tumour has yet to be established.

TP53 tumor suppressor gene and skin carcinogenesis

The tumor suppressor gene TP53 encodes for a nuclear phosphoprotein involved in the control of cell proliferation, particularly in stressed cells. TP53 gene mutations are the most frequent genetic event found in human cancers. Most mutations locate in the highly conserved domains of the gene. Their localizations vary according to the tissue and tumor type, but define some hot spot regions that may have a certain degree of tissue specificity. In certain cases, the type of nucleotide substitutions observed can help to find the carcinogenic agent. In recent years, TP53 gene mutations have been frequently observed in human skin tumors. In epithelial carcinomas, they involve mainly exons 5, 7, and 8. Interestingly, many are C to T transitions at dipyrimidine sites; particularly, one can find CC to TT double-base changes that are known to be specific to ultraviolet radiation. These data confirm at the molecular level the role of ultraviolet radiation as an important etiologic factor in the genesis of these lesions. The high incidence of TP53 mutations suggest that they play a role in keratinocyte transformation. Nevertheless, this event has not yet been defined as an early or late event. In melanomas, most studies have shown the detection of the p53 protein by immunohistochemistry, suggestive of the presence of a mutation in the gene prolonging the protein half-life. Anti-p53 reactivity is frequent in these tumors and seems to correlate with tumor aggressiveness. Confirmation and characterization of TP53 gene mutation at the DNA level would help to precisely define the role of this gene in the development of these tumors.

p53 and PCNA expression in malignant melanomas of the head and neck

Mutation in the p53 tumor suppressor gene is the most common genetic alteration in human cancer. As in mutant p53 the protein is stabilised and the half-life is extended, it becomes detectable by immunohistological staining. p53 immunoreactivity thus seems to be a potential biomarker for the assessment of the oncogenic potential of malignant melanomas. In 103 tissue sections of primary and metastatic malignant melanomas of the head and neck detectable levels of p53 were only found in 3 of the primary tumors and in none of the metastases. At the same time the proliferation status of the malignant melanoma lesions was determined using the cell cycle specific antibody PCNA. 55 primary and metastatic tumors were stained with a PCNA-MAb to determine the proliferation activity of the tumors. The results of our immunohistochemical investigation suggest that immunoreactivity of p53 cannot be used to determine the malignant potential of melanomas in the head and neck. PCNA staining showed that the majority of the tumors and metastases were proliferating rapidly.