Reduced expression of p16 and p27 is correlated with tumour progression in cutaneous melanoma

Cellular senescence in cancer: clinical detection and prognostic implications

Cellular senescence is a state of stable cell-cycle arrest with secretory features in response to cellular stress. Historically, it has been considered as an endogenous evolutionary homeostatic mechanism to eliminate damaged cells, including damaged cells which are at risk of malignant transformation, thereby protecting against cancer. However, accumulation of senescent cells can cause long-term detrimental effects, mainly through the senescence-associated secretory phenotype, and paradoxically contribute to age-related diseases including cancer. Besides its role as tumor suppressor, cellular senescence is increasingly being recognized as an in vivo response in cancer patients to various anticancer therapies. Its role in cancer is ambiguous and even controversial, and senescence has recently been promoted as an emerging hallmark of cancer because of its hallmark-promoting capabilities. In addition, the prognostic implications of cellular senescence have been underappreciated due to the challenging detection and sparse in and ex vivo evidence of cellular senescence in cancer patients, which is only now catching up. In this review, we highlight the approaches and current challenges of in and ex vivo detection of cellular senescence in cancer patients, and we discuss the prognostic implications of cellular senescence based on in and ex vivo evidence in cancer patients.

The markers auxiliary in differential diagnosis of early melanomas and benign nevi sharing some similar features potentially leading to misdiagnosis - a review of immunohistochemical studies

Although most melanocytic skin lesions are correctly diagnosed, numerous studies have shown interobserver disagreement. This review analyzes 20 molecules as immunohistochemical markers for distinguishing dysplastic and/or Spitz nevi from early melanomas (in situ, Clark level I or II and/or Breslow thickness at most 1 mm). The detected presence and/or level of tested molecules was significantly different in early melanomas than in dysplastic and Spitz nevi for six and seven potential markers, respectively. The most promising results were obtained for 5-hydroxymethylcytosine, cyclooxygenase-2 and PReferentially expressed Antigen in MElanoma whose levels were different in dysplastic and Spitz nevi compared to early melanomas.

Targeting CDK4/6 Represents a Therapeutic Vulnerability in Acquired BRAF/MEK Inhibitor-Resistant Melanoma

There is a clear need to identify targetable drivers of resistance and potential biomarkers for salvage therapy for patients with melanoma refractory to the combination of BRAF and MEK inhibition. In this study, we performed whole-exome sequencing on BRAF-V600E-mutant melanoma patient tumors refractory to the combination of BRAF/MEK inhibition and identified acquired oncogenic mutations in NRAS and loss of the tumor suppressor gene CDKN2A We hypothesized the acquired resistance mechanisms to BRAF/MEK inhibition were reactivation of the MAPK pathway and activation of the cell-cycle pathway, which can both be targeted pharmacologically with the combination of a MEK inhibitor (trametinib) and a CDK4/6 inhibitor (palbociclib). In vivo, we found that combination of CDK4/6 and MEK inhibition significantly decreased tumor growth in two BRAF/MEK inhibitor-resistant patient-derived xenograft models. In vitro, we observed that the combination of CDK4/6 and MEK inhibition resulted in synergy and significantly reduced cellular growth, promoted cell-cycle arrest, and effectively inhibited downstream signaling of MAPK and cell-cycle pathways in BRAF inhibitor-resistant cell lines. Knockdown of CDKN2A in BRAF inhibitor-resistant cells increased sensitivity to CDK4/6 inhibition alone and in combination with MEK inhibition. A key implication of our study is that the combination of CDK4/6 and MEK inhibitors overcomes acquired resistance to BRAF/MEK inhibitors, and loss of CDKN2A may represent a biomarker of response to the combination. Inhibition of the cell-cycle and MAPK pathway represents a promising strategy for patients with metastatic melanoma who are refractory to BRAF/MEK inhibitor therapy.

CDK4/6 Inhibitors in Melanoma: A Comprehensive Review

Historically, metastatic melanoma was considered a highly lethal disease. However, recent advances in drug development have allowed a significative improvement in prognosis. In particular, BRAF/MEK inhibitors and anti-PD1 antibodies have completely revolutionized the management of this disease. Nonetheless, not all patients derive a benefit or a durable benefit from these therapies. To overtake this challenges, new clinically active compounds are being tested in the context of clinical trials. CDK4/6 inhibitors are drugs already available in clinical practice and preliminary evidence showed a promising activity also in melanoma. Herein we review the available literature to depict a comprehensive landscape about CDK4/6 inhibitors in melanoma. We present the molecular and genetic background that might justify the usage of these drugs, the preclinical evidence, the clinical available data, and the most promising ongoing clinical trials.

Advances in cyclin-dependent kinase inhibitors for the treatment of melanoma

Introduction: Despite the recent advances in the treatment of malignant melanoma with immunotherapy and BRAF/MEK targeted agents, advanced disease still beholds a poor prognosis for a significant proportion of patients. Cyclin-dependent kinase (CDK) inhibitors have been investigated as novel melanoma therapeutics throughout a range of phase 1 and 2 trials, as single agents and in combination with established treatments. Areas covered: This article summarizes the rationale for, and development of CDK inhibitors in melanoma, with their evolution from pan-CDK inhibitors to highly specific agents, throughout clinical trials and finally their potential future use. Expert opinion: Whilst CDK inhibitors have been practice changing in breast cancer management, their efficacy is yet to be proven in melanoma. Combination with BRAF/MEK inhibitors has been hindered by dose-limiting toxicities, but their role may yet to be found within the spectrum of biomarker-derived personalized melanoma management. The effect that CDK inhibitors can have as an adjunct to immunotherapy also remains to be seen.

Getting under the skin: The role of CDK4/6 in melanomas

Melanoma is the deadliest type of cancer that affects the largest organ of our body, the skin. In recent years, there is an increase in the incidence and aggressiveness of melanomas. The number of treatment options has grown considerably in the past few years, leading to significant improvements in both overall and progression-free survival. One of the attractive candidates in this wave of treatment options is a cell cycle controller: cyclin-dependent kinases (CDK) 4/6 inhibitors. CDK4/6, a class of serine/threonine kinases expressed in most cell types, controls the first gap phase (G1 to S) of the cell cycle, indicating its vital importance in both normal cellular processes as well as tumorigenesis. Up to 90% of melanoma patients have genomic mutations affecting various parts of CDK4/6 pathway. Noticeably, with the help of next-generation sequencing technology, mutations with high frequency in the CDK4 pathway were also identified in relatively rare subtypes of melanoma including acral melanoma and mucosal melanoma. Therefore, CDK4/6 inhibitors have emerged as powerful and promising anticancer therapies, especially in combination treatment with immunotherapies or other targeted therapies. In this review, we will provide an overview of current scientific knowledge regarding the oncogenic properties of CDK4/6 in melanomas, we mainly discuss the latest genomic and preclinical findings of CDK4 signaling in melanoma, the progress of CDK4 inhibition as combined with other therapies for overcoming resistance and summarize recent advances from clinical trials as well as ongoing studies which gives us a better scope into the effectiveness of CDK4/6 therapy in treating malignant melanomas.

NLS-RARα contributes to differentiation block and increased leukemogenic potential in vivo

The fusion oncogene, promyelocytic leukemia (PML)-retinoic acid receptor-α (RARα), is crucial for acute promyelocytic leukemia (APL) pathogenesis. Previous studies have reported that PML-RARα is cleaved by neutrophil elastase (NE), an early myeloid-specific serine protease, leading to translocation of the nuclear localization signal (NLS) of the PML protein to the N-terminal of RARα. This study was designed to evaluate the value of NLS-RARα in the early diagnosis of APL. To investigate the potential functional role of NLS-RARα in leukemogenesis, HL-60 and U937 cell lines were transfected with NLS-RARα lentivirus and negative control (LVNC). The results showed that the induced expression of NLS-RARα down-regulated expressions of CD11b, CD11c, and CD14 compared to the LVNC group induced by 1α, 25-dihydroxyvitamin D₃(1,25(OH)₂D₃). This suggested that NLS-RARα overexpression inhibited granulocytic and monocytic differentiation of myeloid leukemia cells. In addition, Wright-Giemsa staining, flow cytometry, respiratory burst assay, and NBT reduction assay all confirmed the importance of NLS-RARα in differentiation. The mechanistic investigations revealed that induced NLS-RARα expression inhibited 1,25(OH)₂D₃-induced granulocytic differentiation by regulating the cell cycle regulators p19^INK4D, p21^WAF1/CIP1, cyclinD1, cyclin E1, and pRB. Furthermore, the cleaved protein NLS-RARα enhanced the oncogenicity of U937 cells in NOD/SCID mice. These findings collectively demonstrated that NLS-RARα blocked granulocytic and monocytic differentiation of myeloid leukemia cells by inhibiting the downstream targets of the RARα signal pathway and the cell cycle. This may provide a promising new target and method for diagnosing and treating APL.

Immunohistochemical Expression of p16 in Melanocytic Lesions: An Updated Review and Meta-analysis

CONTEXT

- Making an accurate diagnosis for melanocytic lesions has always been challenging for pathologists, especially when dealing with difficult-to-diagnose cases. Misdiagnosis of melanoma and melanocytic lesions in general has tremendous medical-legal implications, often leading to unnecessary and excessive use of adjunctive tests. Although molecular testing is of much interest and there is great support for its development, currently, for most melanocytic lesions, immunohistochemical studies remain the most practical method for assistance in the routine diagnosis of melanocytic lesions for the average pathologist.

OBJECTIVES

- To review the practical use of p16 immunohistochemistry for evaluating melanocytic lesions, particularly for differentiating benign from malignant tumors, and to perform a meta-analysis of primary studies evaluating p16 immunohistochemistry in melanocytic lesions.

DATA SOURCES

- A PubMed database search for literature reporting melanocytic lesions and p16 immunohistochemistry was performed. Essential information from each study (number of samples, antibody used, collection dates, overall p16 immunohistochemistry results, and general method of interpretation) was tabulated and analyzed. Examples of representative cases showing p16 immunostaining pattern are also illustrated.

CONCLUSIONS

- Incorporation of p16 immunohistochemistry for the diagnosis of melanocytic lesions is of limited use, especially for the purpose of differentiating benign from malignant lesions. Evaluation of multiple studies reveals a wide range of results. However, there appears to be some value for the use of p16 in distinguishing nodal nevi from metastatic melanoma within nodes. The method of interpretation (nuclear versus cytoplasmic staining) also appears to give differing results, as studies considering only nuclear staining appeared to show more consistent results from study to study.

Loss of p27kip1 expression is associated with poor prognosis in patients with taxane-treated breast cancer

PURPOSE

Decreased expression of p27^kip1 and p57^kip2 is considered as a prognostic indicator in patients with breast cancer receiving adjuvant chemotherapy. Previous in vitro studies have reported that reduced expression of p27^kip1 and p57^kip2 is associated with resistance to taxane, which is one of the most effective chemotherapeutic agents. In this study, we investigated the association of low p27^kip1 and p57^kip2 expression with outcomes in patients with breast cancer.

METHODS

We investigated 226 cases of breast cancer from Kangbuk SMC between 2000 and 2005. Levels of p27^kip1 and p57^kip2 expression were evaluated using immunohistochemical staining of tumor tissue microarray specimens. The relationships between the expression levels of the markers and patients' outcomes were analyzed using the Kaplan-Meier method and Cox proportional hazard model.

RESULTS

Low p57^kip2 expression was only associated with negative progesterone receptor status (p = 0.034), whereas p27^kip1 expression was associated with poor prognosis of patients receiving adjuvant chemotherapy (p = 0.005). More detailed analysis revealed that low p27^kip1 expression affects the overall survival rate of patients receiving adjuvant chemotherapy including taxane (p = 0.026), but not that of patients receiving chemotherapy without taxane.

CONCLUSIONS

Low p27^kip1 expression may be useful to predict overall survival in patients with breast cancer who are treated with taxane. Evaluation of p27^kip1 expression may provide further prognostic information beyond traditional prognostic biomarkers and an understanding of the mechanisms that impart resistance against chemotherapy.

CKS1 expression in melanocytic nevi and melanoma

Cyclin-dependent kinase subunit 1 (Cks1) regulates the degradation of p27, an important G1-S inhibitor, which is up regulated by MAPK pathway activation. In this study, we sought to determine whether Cks1 expression is increased in melanocytic tumors and correlates with outcome and/or other clinicopathologic prognostic markers. Cks1 expression was assessed by immunohistochemistry in 298 melanocytic lesions. The frequency and intensity of cytoplasmic and nuclear expression was scored as a labeling index and correlated with clinico-pathological data. Nuclear Cks1 protein was found in 63% of melanocytic nevi, 89% primary and 90% metastatic melanomas with mean labeling index of 7 ± 16, 19 ± 20, and 30 ± 29, respectively. While cytoplasmic Cks1 was found in 41% of melanocytic nevi, 84% primary and 95% metastatic melanomas with mean labeling index of 18 ± 34, 35 ± 34, and 52 ± 34, accordingly. Histologic stepwise model of tumor progression, defined as progression from benign nevi to primary melanomas, to melanoma metastases, revealed a significant increase in nuclear and cytoplasmic Cks1 expression with tumor progression. Nuclear and cytoplasmic Cks1 expression correlated with the presence of ulceration, increased mitotic rate, Breslow depth, Clark level, tumor infiltrating lymphocytes and gender. However, other well-known prognostic factors (age, anatomic site, and regression) did not correlate with any type of Cks1 expression. Similarly, increasing nuclear expression of Cks1 significantly correlated with worse overall survival. Thus, Cks1 expression appears to play a role in the progression of melanoma, where high levels of expression are associated with poor outcome. Cytoplasmic expression of Cks1 might represent high turnover of protein via the ubiquination/proteosome pathway.

Cell Cycle Regulation and Melanoma

Dysregulation of cell cycle control is a hallmark of melanomagenesis. Agents targeting the G1-S and G2-M checkpoints, as well as direct anti-mitotic agents, have all shown promising preclinical activity in melanoma. However, in vivo, standalone single agents targeting cell cycle regulation have only demonstrated modest efficacy in unselected patients. The advent of specific CDK 4/6 inhibitors targeting the G1-S transition, with an improved therapeutic index, is a significant step forward. Potential synergy exists with the combination of CDK4/6 inhibitors with existing therapies targeting the MAPK pathway, particularly in subsets of metastatic melanomas such as NRAS and BRAF mutants. This reviews summaries of the latest developments in both preclinical and clinical data with cell cycle-targeted therapies in melanoma.

Cyclin D1 and p16 Expression in Blue Nevi and Malignant Melanoma

BACKGROUND

Differentiating benign blue nevi from blue nevus-like melanoma can be diagnostically challenging. We aimed to determine the utility of immunohistochemical staining for p16 and cyclin D1 in distinguishing benign blue nevi and malignant melanoma.

MATERIALS AND METHODS

Thirty-two biopsy specimens taken between 2007 and 2015 were obtained from the Department of Pathology at the Queen's Medical Center in Honolulu, HI. These included 9 common blue nevi, 8 cellular blue nevi (2 with atypical features), and 15 malignant melanomas (3 blue nevus-like melanoma). The primary outcome was the difference in p16 and cyclin D1 staining between benign blue nevi and malignant melanoma. Staining of specimens for p16 and cyclin D1 was graded on the strength of staining, and the percent of tumor that stained positive. A specimen was deemed positive if it showed 2+ staining in ≥50% of the tumor.

RESULTS

The majority (82%) of blue nevi stained negative for p16. There was not a significant difference between p16 staining in benign blue nevi and melanoma (P=0.06). Eleven (73%) melanomas stained positive for cyclin D1 with a sensitivity of 0.73 and positive predictive value of 1.0. All blue nevi were negative for cyclin D1, making its specificity 1.0 and its negative predictive value 0.8. This difference in cyclin D1 staining in blue nevi and melanoma was significant (P=0.0001).

CONCLUSIONS

Cyclin D1 may be useful in differentiating benign blue nevi from melanoma.

A small multimarker panel using simple immunohistochemistry methods is an adjunct to stage for cutaneous melanoma prognosis

Melanoma is an aggressive cancer. Outcomes can vary significantly for lesions within the same pathological stage - a problem of increasing relevance with the promise of adjuvant treatments on the basis of immune checkpoint modulators and targeted therapies. The use of a panel of prognostic molecular biomarkers as an adjunct to stage represents a possible solution. Immunohistochemistry-based biomarkers offer greater potential for translation into clinical practice than biomarkers utilizing more complex methods. Many immunohistochemistry-based biomarkers have been identified through discovery studies, but rigorous validation of these is scarce. We take the first steps towards validating a combination of three such biomarkers in a prognostic panel - 5hmC, ki-67 and p16. Immunohistochemistry was performed on a cohort of 50 melanomas to determine the expression of 5hmC, ki-67 and p16. 5hmC and p16 showed statistically significant differences in metastasis-free survival between low-score and high-score groups, whereas the use of all three biomarkers together with stage could predict the 5-year metastasis risk more accurately than stage alone. Our results suggest that the use of multimarker panels to improve the accuracy of prognostic predictions is feasible and worthy of further study. We have shown that a small immunohistochemistry-based panel utilizing simple, inexpensive, reproducible methods can be an effective adjunct to stage in prognostic prediction. A follow-up study consisting of a large cohort of melanomas is now indicated to continue the development of the prognostic panel.

Induction of Therapeutic Senescence in Vemurafenib-Resistant Melanoma by Extended Inhibition of CDK4/6

Dysregulation of the p16-cyclin D1-CDK4/6-Rb pathway occurs frequently in melanoma; however, the therapeutic efficacy of CDK4/6 inhibition remains to be critically evaluated. We demonstrate that CDK4/6 inhibition inhibits melanoma progression through induction of senescence. Palbociclib, a specific CDK4/6 inhibitor, rapidly induces cell cycle arrest within 24 hours and continued exposure for 8 days or longer induces senescence. The induction of senescence correlates with inhibition of mTOR and more specifically mTORC1 signaling. Vemurafenib, a specific BRAF(V600E) inhibitor, has significant clinical efficacy in BRAF(V600E)-positive melanomas, but its impact is hampered by a rapid acquisition of resistance. Strikingly, we found that vemurafenib-resistant tumors remain sensitive to palbociclib, suggesting that initial treatment with vemurafenib followed by palbociclib with or without mTOR inhibitors might provide an avenue to overcome recurrence of vemurafenib-resistant metastatic disease. Taken together, these results support palbociclib as a promising therapeutic for treatment of melanoma. Cancer Res; 76(10); 2990-3002. ©2016 AACR.

CDK4 inhibitors an emerging strategy for the treatment of melanoma

Research into the cyclin-dependent kinases and their inhibitors is finally coming into the forefront of clinical research in cancer. Targeted therapies such as BRAF inhibitors have led the way in improving treatment outcomes in advanced melanoma. Based on detailed genomic knowledge of melanoma it is now time to extend targeted therapies beyond BRAF to fulfill the vision of precision medicine. The p16^INK4A-cyclin D-CDK4/6-retinoblastoma protein pathway (RB pathway) is dysregulated in more than 90% of melanomas and interacts biochemically and genetically with the RAS/RAF/MEK/ERK pathway. Recognizing and understanding these processes that drive melanomagenesis is essential to rationally develop new therapies. This paper reviews the mechanisms, background and progress of small molecule CDK4 inhibitors in the management of melanoma.

Loss of CDKN2A expression is a frequent event in primary invasive melanoma and correlates with sensitivity to the CDK4/6 inhibitor PD0332991 in melanoma cell lines

We have investigated the potential for the p16-cyclin D-CDK4/6-retinoblastoma protein pathway to be exploited as a therapeutic target in melanoma. In a cohort of 143 patients with primary invasive melanoma, we used fluorescence in situ hybridization to detect gene copy number variations (CNVs) in CDK4, CCND1, and CDKN2A and immunohistochemistry to determine protein expression. CNVs were common in melanoma, with gain of CDK4 or CCND1 in 37 and 18% of cases, respectively, and hemizygous or homozygous loss of CDKN2A in 56%. Three-quarters of all patients demonstrated a CNV in at least one of the three genes. The combination of CCND1 gain with either a gain of CDK4 and/or loss of CDKN2A was associated with poorer melanoma-specific survival. In 47 melanoma cell lines homozygous loss, methylation or mutation of CDKN2A gene or loss of protein (p16(INK) (4A) ) predicted sensitivity to the CDK4/6 inhibitor PD0332991, while RB1 loss predicted resistance.

p16 Expression Is Lost in Severely Atypical Cellular Blue Nevi and Melanoma Compared to Conventional, Mildly, and Moderately Atypical Cellular Blue Nevi

Background. Significant decreases in p16 expression have been shown to occur in melanoma compared to Spitz tumors, and loss of p16 staining has been found to correlate with melanoma tumor progression. However, comparison of p16 between atypical cellular blue nevi (CBN) and melanoma has not been reported previously. Methods. p16 immunohistochemical staining was evaluated in 14 atypical CBN, 8 conventional and atypical melanocytic nevi, and 16 melanomas, including 4 malignant CBN. p16 staining intensity was graded on a scale of 0–3 and the percentage of melanocytes stained with p16 was determined. Results. p16 staining was significantly higher in all CBN as a group when compared to melanomas (P = 0.001) and malignant CBN (P = 0.00008). Higher p16 expression was also seen in mildly (P = 0.0002) and moderately atypical (P = 0.02), but not severely atypical, CBN compared to melanomas. Conclusions. p16 immunohistochemical expression is higher in mildly and moderately atypical CBN compared to severely atypical CBN and melanomas. In conjunction with additional markers and histology, p16 staining may be useful in confirming the benign nature of these tumors, but is not useful in distinguishing severely atypical CBN from malignant cases, consistent with the overlapping histologic features between these tumors.

Insights into melanoma: targeting the mTOR pathway for therapeutics

INTRODUCTION

Cutaneous melanoma represents < 5% of all skin cancers, but is responsible for the majority of skin cancer-related deaths. Ocular melanoma is the most common primary eye tumor in adults, and accounts for approximately 5% of all melanomas. Despite new diagnostic and therapeutic tools, the overall survival of patients treated for melanoma has not improved and most patients die of metastatic disease. Therefore, clarification of the molecular mechanisms underlying the etiopathogenesis of cutaneous and ocular melanomas may help determining the prognosis and tailoring therapy of patients harboring melanomas.

AREAS COVERED

In this review the authors aim to survey relevant research in the molecular mechanisms underlying melanomagenesis, and therapies under evaluation with emphasis in the mTOR pathway.

EXPERT OPINION

Despite an increasingly understanding of the genetics and biochemistry of melanoma, the mechanisms underlying their complex interactions are still poorly understood. Their clarification will lead to more successful therapeutic strategies and evidence-based management of patients with melanoma. More active drug combinations together with appropriate melanoma patient stratification based on molecular biomarkers will be essential for new advances in melanoma therapy.

Prognostic significance of cytoplasmic p27 expression in human melanoma

BACKGROUND

The cyclin-dependent kinase inhibitor p27 plays important roles in cell proliferation, cell motility, and apoptosis. Interestingly, the nuclear and cytoplasmic p27 exert opposite biological functions. In this study, we investigated the prognostic impact of subcellular p27 expression.

METHODS

We constructed melanoma tissue microarrays in a large series of melanoma patients, including 29 normal nevi, 52 dysplastic nevi, 270 primary melanomas, and 148 metastatic melanomas. The expression level of subcellular p27 in different stages of melanocytic lesions and its prognostic significance were evaluated.

RESULTS

Compared with dysplastic nevi, nuclear p27 expression was remarkably reduced in primary melanomas and further reduced in metastatic melanoma (P < 0.001 for both), whereas cytoplasmic p27 expression is significantly increased from dysplastic nevi to primary melanomas (P = 0.032) and further increased in melanoma metastases (P = 0.037). Although loss of nuclear p27 expression is correlated with a worse 5-year survival of primary melanoma patients in Kaplan-Meier analysis (P = 0.046), it is not a prognostic factor by multivariate Cox regression analysis. On the contrary, Kaplan-Meier analysis showed that gain of cytoplasmic p27 was associated with a poor 5-year survival of metastatic melanoma patients (P < 0.001). Multivariate Cox regression analysis revealed that positive cytoplasmic p27 expression is an independent prognostic factor to predict metastatic melanoma patient outcome.

CONCLUSION

Cytoplasmic p27 may serve as a promising prognostic marker for metastatic melanoma.

IMPACT

Because there is no reliable prognostic marker for metastatic melanoma, our finding may have important clinical implications using cytoplasmic p27 as a prognostic biomarker for advanced melanoma.

Immune-related biomarkers for diagnosis/prognosis and therapy monitoring of cutaneous melanoma

Skin melanoma, a life-threatening disease, has a recently reported worldwide increase in incidence, despite primary prevention. Skin melanoma statistics emphasize the need for finding markers related to the immune response of the host. The mechanisms that are able to over-power the local immune surveillance comprise molecules that can be valuable markers for diagnosis and prognosis. This article summarizes the immune markers that can monitor the disease stage and evaluate the efficacy of therapeutic interventions. Recent data regarding immunotherapy are presented in the context of tumor escape from immune surveillance and the immune molecules that are both targets and a means of monitoring. Perspectives for developing immune interventions for skin melanoma management and the position of tissue or soluble immune markers as a diagnostic/prognostic panel are evaluated. State-of-the-art technology is emphasized for developing immune molecular signatures for a complex characterization of the patient's immunological status.

Histologically ambiguous ("borderline") primary cutaneous melanocytic tumors: approaches to patient management including the roles of molecular testing and sentinel lymph node biopsy

It is well recognized that the pathologic diagnosis of melanocytic tumors can sometimes be difficult. For some atypical melanocytic tumors that do not display clear-cut features of malignancy, it may be difficult or impossible to exclude a diagnosis of melanoma; this includes those showing some resemblance to Spitz nevi, blue nevi, deep penetrating nevi, and possible nevoid melanomas. When there is uncertainty about whether a primary melanocytic tumor is a nevus or a melanoma, we recommend that a second opinion be sought from one or more experienced colleagues. If diagnostic uncertainty persists, the evidence for or against the various differential diagnostic considerations should be presented in the pathology report and a "most likely" or "favored" diagnosis given. Molecular testing of the primary tumor by using techniques such as comparative genomic hybridization or fluorescence in situ hybridization may assist in establishing a diagnosis of melanoma if multiple chromosomal aberrations are identified. However, these tests require further independent validation and are not widely available at present. Complete excision of the lesion is probably mandatory, but plans for further management should be formulated on a case-by-case basis. While the safest course of action will usually be to manage the tumor as if it were a melanoma (taking into account the tumor's thickness and other prognostic variables), this may not always be appropriate, particularly if it is located in a cosmetically sensitive site such as the face. In some cases, it may be appropriate for the surgical oncologist to convey the diagnostic uncertainty to patients and to present them with management choices so that they can decide whether they wish to be managed aggressively (as for a melanoma) or conservatively. While a sentinel lymph node biopsy may be recommended on the basis of the primary tumor characteristics, the clinical significance of lymph node involvement for these tumors is not yet clear, and it may not have the same prognostic implications as nodal involvement from an unequivocal "conventional" melanoma.

Cell cycle control of β-cell replication in the prenatal and postnatal human pancreas

β-Cell regeneration declines with aging, but the molecular mechanisms controlling β-cell replication in humans are not well understood. We compared the expression of selected cell cycle proteins in prenatal and adult tissue and examined the association of these proteins with β-cell replication. Pancreatic tissue from a total of 20 human fetuses and adults was stained for Ki67, cyclin D3, p16 and p27, and insulin. The β-cellular expression of these cell cycle proteins was determined. The frequency of β-cell replication was lower in adult compared with prenatal β-cells (<0.5 vs. 3.4 ± 0.5%, respectively; P < 0.0001). p16 was sporadically expressed in prenatal β-cells (8.0 ± 1.1%) but highly enriched in adult β-cells (63.1 ± 5.2%, P < 0.0001). Likewise, the expression of p27 was much lower in prenatal β-cells (1.7 ± 0.4 vs. 44.1 ± 5.4%, respectively, P < 0.0001), and cyclin D3 expression increased from 24.2 ± 4.1 to 47.25 ± 5.0%, respectively (P < 0.001), with aging. The expression of all three proteins was significantly correlated with each other (P < 0.01 and r > 0.75, respectively). The strong expression of cyclin D3 in adult human β-cells and its correlation to p27 and p16 suggest a positive role in human β-cell cycle regulation. p16 and p27 appear to restrict β-cell replication with aging. The age dependency of cell cycle regulation in human β-cells might explain the reduced β-cell regeneration in adult humans.

High frequency of p16(INK4A) promoter methylation in NRAS-mutated cutaneous melanoma

The p16(INK4A) tumor suppressor is often deleted, or otherwise inactivated, in malignant melanoma. To investigate the loss of p16(INK4A) in greater detail, we analyzed 77 cutaneous melanoma metastases. Of these 56 retained at least one p16(INK4A) allele, and 21 had biallelic deletions. Using methylation-specific PCR, direct sequencing, and immunohistochemical methods, we analyzed p16(INK4A) promoter methylation, mutations, and protein expression, respectively. In addition, 14 corresponding primary tumors were analyzed for protein expression. Results were compared to clinicopathological parameters and previously obtained data regarding mutations in proto-oncogenes NRAS and BRAF. Results revealed that p16(INK4A) promoter methylation was present in 15 of 59 (25%) metastases; nonsynonymous mutations in 9 of 56 (16%) metastases; and protein expression in 12 of 67 (18%) metastases. Protein expression was lost during progression from primary to metastatic tumors, 71% (10 of 14) and 43% (6 of 14) being positive, respectively. However, the genetic and epigenetic alterations of p16(INK4A) observed could not explain the lack of p16(INK4A) protein in 27 metastases, indicating the presence of additional inactivating mechanisms for p16(INK4A). Interestingly, p16(INK4A) promoter methylation was significantly overrepresented in NRAS-mutated samples compared to NRAS wild-type samples (P=0.0004), indicating an association between these two events.

Dormancy of metastatic melanoma

Metastatic dormancy of melanoma has not received sufficient attention, most likely because once detectable, metastasis is almost invariably fatal and, understandably, the focus has been on finding ways to prolong life of patients with overt recurrences. Nevertheless, analysis of the published clinical and experimental data on melanoma indicates that some aspect of melanoma biology imitate traits recently associated with dormancy in other solid cancers. Among them the ability of some melanomas to disseminate early during primary tumor progression and once disseminated, to remain undetected (dormant) for years. Comparison of cutaneous and uveal melanoma indicates that, in spite of being of the same origin, they differ profoundly in their clinical progression. Importantly for this discussion, between 40 and 50% of uveal melanoma remain undetected for longer than a decade, while less than 5% of cutaneous melanoma show this behavior. Both types of melanoma have activating oncogene mutations that provide autonomous pro-proliferative signals, yet the consensus is that those are not sufficient for tumor progression. If that is the case, it is possible to envision that signals from outside the tumor cell, (microenvironment) shape the fate of an individual disseminated cell, regardless of an oncogene mutation, to progress or to pause in a state of dormancy. To stimulate further debate and inquiry we describe here a few examples of potential signals that might modify the fate of disseminated cell and provide brief description of the current knowledge on dormancy in other cancers. Our hope is to convince the reader that disseminated melanoma cells do enter periods of prolonged dormancy and that finding ways to induce it, or to prolong it, might mean an extension of symptoms-free life for melanoma patients. Ultimately, understanding the biology of dormancy and the mechanisms of dormant cell survival, might allow for their specific targeting and elimination.

Reduced p16 and increased cyclin D1 and pRb expression are correlated with progression in cutaneous melanocytic tumors

The immunohistochemical expression of cell cycle proteins p16, cyclin D1, and pRb was assessed in 112 benign and malignant melanocytic tumors and correlated with tumor progression, prognosis, and outcome. Comparing benign and malignant tumors, there were significant differences in the median score for all 3 proteins, with decreased p16 (P = .000001), increased cyclin D1 (P = .01), and increased pRb in melanomas (P = .01). There was a progressive loss of expression of p16 with progression from benign naevi to primary melanomas and to metastases. p16 was significantly decreased in primary tumors from melanoma patients who developed recurrent disease (P = .0000013). Cyclin D1 and pRb showed a progressive increase in expression from benign to malignant tumors but with relative decreases in the more advanced tumors (thick primaries and metastatic melanomas). Alterations in cell cycle proteins involved in G1/S transition are implicated in melanocytic tumor progression and have a potential role in diagnosis and prognostication.

Suberythemal ultraviolet B radiation alters the expression of cell cycle-related proteins in the epidermis of human subjects without leading to photoprotection

BACKGROUND

Deregulation of the cell cycle proteins is one of the critical factors leading to cutaneous carcinogenesis.

OBJECTIVES

To monitor the expression of cell cycle proteins in the epidermis of subjects after repeated exposure to ultraviolet (UV) B radiation, and to test for the development of photoprotection by subsequent irradiation with a single erythemal UVB dose.

METHODS

A total of 26 healthy volunteers were divided into four groups: group 1 (n = 9) were given whole-body UVB irradiation for 10 consecutive days with 0.7 minimal erythema dose (MED), group 2 (n = 9) were irradiated as in group 1 followed 24 h later by a single UVB dose of 3 MED on buttock skin, group 3 (n = 4) were irradiated with a UVB dose of 3 MED on buttock skin, and group 4 (n = 4) were not irradiated. Skin biopsies were collected 24 h after the final irradiation and stained for cyclins A, B1, D1, and p16, p18, p21, p27, p53, pRB, Bax and Bcl-2.

RESULTS

The expression of cyclin D1, p18 and p21 was significantly higher in groups 1 and 2 compared with the nonirradiated group 4 controls and, in group 2, the expression of pRB, p53 and Bax was also increased. In group 3, only p53 and Bax proteins were significantly elevated compared with group 4. The expression of cyclin D1, p16, p18, p27, pRB and Bcl-2 was higher in group 2 compared with group 3.

CONCLUSIONS

Suberythemal UVB radiation was sufficient to cause changes in the expression of several epidermal cell cycle proteins. When tested by irradiation with a single erythemal UVB dose following the repeated exposures, no photoprotection against the UV-induced alteration in cell cycle protein expression was apparent.

Oncogenic Braf induces melanocyte senescence and melanoma in mice

We show here that inducible expression of Braf(V600E) off the endogenous Braf gene in mouse melanocytes stimulates skin hyperpigmentation and the appearance of nevi harboring senescent melanocytes. Additionally, approximately 70% of Braf(V600E) mice develop melanomas that reproduce many of the cardinal histological and molecular features of human melanoma and whose cells can colonize the lungs of nude mice. We show that the tumor suppressor p16(INK4a) is not required to induce melanocyte senescence and that its loss is not required for tumor progression, although it does regulate tumor penetrance and latency. Thus, we have developed a mouse model of melanoma driven by Braf(V600E) expressed at physiological levels that reflects the genetics and pathology of the human disease.

Bypassing melanocyte senescence by beta-catenin: a novel way to promote melanoma

The Wnt/beta-catenin signaling pathway plays a key role in several cellular functions during embryonic development and adult homeostasis. The deregulation of this pathway may lead to the development of cancer, including melanoma. Deregulation of the Wnt/beta-catenin pathway occurs through either the induction/repression of, or specific mutations in, various members of this signaling pathway; this results in the stabilization of beta-catenin and its translocation from the cytoplasm to the nucleus, where it regulates transcription. Although nuclear beta-catenin is clearly involved in malignant transformation, the mechanism by which it exerts its effects remains elusive. This review focuses on the molecular and cellular mechanisms that are driven by beta-catenin and lead to melanocyte transformation. In particular, we describe how beta-catenin induces melanocyte immortalization, a novel activity of this multifunction protein. Finally, we discuss how beta-catenin-induced immortalization can cooperate with MAPKinase pathways to produce melanoma.