Merkel Cell Carcinoma from Molecular Pathology to Novel Therapies

All-trans retinoic acid exhibits anti-proliferative and differentiating activity in Merkel cell carcinoma cells via retinoid pathway modulation

BACKGROUND

The limited therapies available for treating Merkel cell carcinoma (MCC), a highly aggressive skin neoplasm, still pose clinical challenges, and novel treatments are required. Targeting retinoid signalling with retinoids, such as all-trans retinoic acid (ATRA), is a promising and clinically useful antitumor approach. ATRA drives tumour cell differentiation by modulating retinoid signalling, leading to anti-proliferative and pro-apoptotic effects. Although retinoid signalling is dysregulated in MCC, ATRA activity in this tumour is unknown. This study aimed to evaluate the impact of ATRA on the pathological phenotype of MCC cells.

METHODS

The effect of ATRA was tested in various Merkel cell polyomavirus-positive and polyomavirus-negative MCC cell lines in terms of cell proliferation, viability, migration and clonogenic abilities. In addition, cell cycle, apoptosis/cell death and the retinoid gene signature were evaluated upon ATRA treatments.

RESULTS

ATRA efficiently impaired MCC cell proliferation and viability in MCC cells. A strong effect in reducing cell migration and clonogenicity was determined in ATRA-treated cells. Moreover, ATRA resulted as strongly effective in arresting cell cycle and inducing apoptosis/cell death in all tested MCC cells. Enrichment analyses indicated that ATRA was effective in modulating the retinoid gene signature in MCC cells to promote cell differentiation pathways, which led to anti-proliferative and pro-apoptotic/cell death effects.

CONCLUSIONS

These results underline the potential of retinoid-based therapy for MCC management and might open the way to novel experimental approaches with other retinoids and/or combinatorial treatments.

Merkel Cell Carcinoma on the Face: Case Report

Merkel cell carcinoma (MCC) is a rare primary neuroendocrine skin tumor that presents as a flesh-colored or bluish-red nodule on the face, neck, or head. Long-term ultraviolet radiation exposure and Merkel cell polyomavirus are associated with MCC pathogenesis. We present a case of MCC on the right cheek in a male patient aged 87 years. Our primary goal in presenting the case is to bring MCC, which is a diagnostic challenge, to the notice of dermatologists and oncologists, as early detection and prompt treatment are important. The patient had a significant past medical history, including diabetes mellitus, hypertension, dyslipidemia, stage 3 chronic kidney disease, benign prostatic hyperplasia, chronic hyponatremia, acute pancreatitis, essential thrombocytosis on hydroxyurea, and ischemic heart disease. The patient presented with a mildly swollen right upper lip showing a poorly defined, relatively homogeneous subcutaneous lesion with a history of persistence for 1.5 months. The clinical examination revealed a 5 × 3-cm nodular lesion on the right side of the cheek with swelling of the right upper lip. Immunohistochemistry markers and histopathological features confirmed the diagnosis of MCC. The patient was referred to the oncology department for further management. MCC of the skin is an aggressive lesion with a high risk of metastasis and recurrence, which is more common in immunocompromised people. Prompt management and treatment of MCC is essential because if left untreated, it can spread to other parts of the body and can also metastasize to lymph nodes and other organs. The patient is 87 years old and has a significant past medical history of diabetes mellitus, hypertension, dyslipidemia, chronic kidney disease stage 3, benign prostatic hyperplasia, chronic hyponatremia, acute pancreatitis, essential thrombocytosis on hydroxyurea, and ischemic heart disease. Currently, the patient presented with a mildly swollen right upper lip showing a poorly defined, relatively homogenous subcutaneous lesion with a history of persistence for 1.5 months. The clinical examination revealed a 5x3 cm nodular lesion on the right side of the cheek with swelling of the right upper lip. Immunohistochemistry markers results and histopathological features confirmed the diagnosis of Merkel cell carcinoma. The patient was referred to the oncology department for further management. Merkel cell carcinoma of the skin is an aggressive lesion with a high risk of metastasis and recurrence, which is more common in immunocompromised people. Prompt management and treatment of Merkel cell carcinoma is essential because if left untreated, it can spread to other parts of the body and can also metastasize to lymph nodes and other organs.

The effect of GP-2250 on cultured virus-negative Merkel cell carcinoma cells: preliminary results

BACKGROUND

Even in the novel immunotherapy era, Merkel cell carcinoma (MCC) remains challenging in its treatment. Apart from Merkel cell polyomavirus (MCPyV) associated MCC, this cancer is linked in about 20% of cases to ultraviolet-induced mutational burden frequently causing aberrations in Notch and PI3K/AKT/mTOR signalling pathways. The recently developed agent GP-2250 is capable to inhibit growth of cells of different cancers, including pancreatic neuroendocrine tumors. The objective of the present study was to investigate the effects of GP-2250 on MCPyV-negative MCC cells.

METHODS

Methods We employed three cell lines (MCC13, MCC14.2, MCC26) which were exposed to different GP-2250doses. GP-2250's effects on cell viability, proliferation, and migration were evaluated by means of MTT, BrdU, and scratch assays, respectively. Flow cytometry was performed for the evaluation of apoptosis and necrosis. Western blotting was implemented for the determination of AKT, mTOR, STAT3, and Notch1 protein expression.

RESULTS

Cell viability, proliferation, and migration decreased with increasing GP-2250 doses. Flow cytometry revealed a dose response to GP-2250 in all three MCC cell lines. While the viable fraction decreased, the share of necrotic and in a smaller amount the apoptotic cells increased. Regarding Notch1, AKT, mTOR, and STAT3 expression a comparatively time- and dose-dependent decrease of protein expression in the MCC13 and MCC26 cell lines was observed. By contrast, Notch1, AKT, mTOR, and STAT3 expression in MCC14.2 was scarcely altered or even increased by the three dosages of GP-2250 applied.

CONCLUSIONS

The present study indicates GP-2250 having anti-neoplastic effects in MCPyV-negative tumor cells in regard to viability, proliferation, and migration. Moreover, the substance is capable of downregulating protein expression of aberrant tumorigenic pathways in MCPyV-negative MCC cells.

The emerging role of miRNAs in Merkel cell carcinoma pathogenesis: Signaling pathway crosstalk

Merkel cell carcinoma (MCC) is an uncommon invasive form of skin cancer that typically manifests as a nodule on the face, head, or neck that is flesh-colored or bluish-red in appearance. Rapid growth and metastasis are hallmarks of MCC. MCC has the second-greatest mortality rate among skin cancers after melanoma. Despite the recent cascade of molecular investigations, no universal molecular signature has been identified as responsible for MCC's pathogenesis. The microRNAs (miRNAs) play a critical role in the post-transcriptional regulation of gene expression. Variations in the expression of these short, non-coding RNAs have been associated with various malignancies, including MCC. Although the incidence of MCC is very low, a significant amount of study has focused on the interaction of miRNAs in MCC. As such, the current survey is a speedy intensive route revealing the potential involvement of miRNAs in the pathogenesis of MCC beyond their association with survival in MCC.

BRCA1/2 Pathogenic Variants Are Not Common in Merkel Cell Carcinoma: Comprehensive Molecular Study of 30 Cases and Meta-Analysis of the Literature

Merkel cell carcinoma (MCC) is a rare and aggressive cutaneous neuroendocrine cancer. Management of advanced MCC is mainly based on immune-checkpoint inhibitors. The high failure rate warrants an investigation of new therapeutic targets. The recent identification of BRCA1 or BRCA2 (BRCA1/2) mutations in some MCC raises the issue of the use of poly-(ADP-Ribose)-polymerase inhibitors in selected advanced cases. The main objective of our study is to determine the accurate frequency of BRCA1/2 pathogenic variants. We studied a series of 30 MCC and performed a meta-analysis of BRCA1/2 variants of published cases in the literature. In our series, we detected only one BRCA2 pathogenic variant. The low frequency of BRCA1/2 pathogenic variants in our series of MCC (3%) was confirmed by the meta-analysis of BRCA1/2 variants in the literature. Among the 915 MCC from 13 published series studied for molecular alterations of BRCA1/2, only 12 BRCA1/2 pathogenic mutations were identified (1-2% of MCC), whereas many other BRCA1/2 variants were variants of unknown significance or benign. BRCA1/2 pathogenic variants are uncommon in MCC. However, in BRCA-mutated MCC, poly-(ADP-Ribose)-polymerase inhibitors might be a valuable therapeutic option requiring validation by clinical trials.

Facial Merkel cell carcinoma in a patient with diabetes and hepatitis B: A case report

BACKGROUND

Patients with chronic inflammatory disorders are at a higher risk of developing aggressive Merkel cell carcinoma (MCC). Diabetes is a common chronic inflammatory disease that is possibly associated with MCC; however, there are still no reports on the association between hepatitis B virus (HBV) infection and MCC. Whether there is an association between these three diseases and the specific mechanisms behind their effects is worth further research in the future.

CASE SUMMARY

We herein report a rare case of MCC with extracutaneous and nodal invasion in an Asian individual with type 2 diabetes mellitus and chronic HBV infection, but no immunosuppression or other malignancies. Such cases are uncommon and have rarely been reported in the literature. A 56-year-old Asian male presented with a significant mass on his right cheek and underwent extensive resection combined with parotidectomy, neck lymphadenectomy, and split-thickness skin grafting. Based on the histopathological findings, a diagnosis of MCC involving the adipose tissue, muscle, nerve, and parotid gland with lymphovascular invasion was made. Subsequently, he received radiotherapy with no adverse reactions.

CONCLUSION

MCC is a rare, aggressive skin cancer with frequent local recurrence, nodal invasion, and metastasis, which usually arises in older people of the white race. Patients with chronic inflammatory disorders are at a higher risk of developing aggressive MCC. The diagnosis can be confirmed with histology and immunohistochemistry. For localized MCC, surgery is the preferred treatment option. However, for advanced MCC, radiotherapy and chemotherapy have proven to be effective. In cases where chemotherapy is not effective or in the advanced stages of MCC, immune therapy plays an important role in treatment. As with any rare disease, the management of MCC remains an enormous challenge for clinicians; thus, follow-up should be individualized and future progress needs multidisciplinary collaborative efforts. Furthermore, physicians should include MCC in their list of possible diagnoses when they come across painless, rapidly growing lesions, particularly in patients with chronic HBV infection or diabetes, as these patients are more susceptible to the development of this condition and it tends to be more aggressive in them.

MicroRNA dysregulations in Merkel cell carcinoma: Molecular mechanisms and clinical applications

Merkel cell carcinoma (MCC) is an aggressive skin malignancy with two distinct etiologies. The first, which accounts for the highest proportion, is caused by Merkel cell polyomavirus (MCPyV), a DNA tumor virus. A second, UV-induced, MCC form has also been identified. Few MCC diagnostic, prognostic, and therapeutic options are available. MicroRNAs (miRNAs) are small noncoding RNA molecules, which play a key role in regulating various physiologic cellular functions including cell cycling, proliferation, differentiation, and apoptosis. Numerous miRNAs are dysregulated in cancer, by acting as either tumor suppressors or oncomiRs. The aim of this review is to collect, summarize, and discuss recent findings on miRNAs whose dysregulation has been assumed to play a role in MCC. The potential clinical application of miRNAs as diagnostic and prognostic biomarkers in MCC is also described. In the future, miRNAs will potentially gain clinical significance for the improvement of MCC diagnostic, prognostic, and therapeutic options.

T-Cell Mediated Immunity in Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is a rare and frequently lethal skin cancer with neuroendocrine characteristics. MCC can originate from either the presence of MCC polyomavirus (MCPyV) DNA or chronic ultraviolet (UV) exposure that can cause DNA mutations. MCC is predominant in sun-exposed regions of the body and can metastasize to regional lymph nodes, liver, lungs, bone, and brain. Older, light-skinned individuals with a history of significant sun exposure are at the highest risk. Previous studies have shown that tumors containing a high number of tumor-infiltrating T-cells have favorable survival, even in the absence of MCPyV DNA, suggesting that MCPyV infection enhances T-cell infiltration. However, other factors may also play a role in the host antitumor response. Herein, we review the impact of tumor infiltrating lymphocytes (TILs), mainly the CD4⁺, CD8⁺, and regulatory T-cell (Tregs) responses on the course of MCC, including their role in initiating MCPyV-specific immune responses. Furthermore, potential research avenues related to T-cell biology in MCC, as well as relevant immunotherapies are discussed.

Merkel Cell Polyomavirus (MCPyV) and Cancers: Emergency Bell or False Alarm?

Merkel cell polyomavirus (MCPyV), the sole member of Polyomavirus associated with oncogenesis in humans, is the major causative factor of Merkel cell carcinoma (MCC), a rare, neuroendocrine neoplasia of the skin. Many aspects of MCPyV biology and oncogenic mechanisms remain poorly understood. However, it has been established that oncogenic transformation is the outcome of the integration of the viral genome into the host DNA. The high prevalence of MCPyV in the population, along with the detection of the virus in various human tissue samples and the strong association of MCPyV with the emergence of MCC, have prompted researchers to further investigate the role of MCPyV in malignancies other than MCC. MCPyV DNA has been detected in several different non-MCC tumour tissues but with significantly lower prevalence, viral load and protein expression. Moreover, the two hallmarks of MCPyV MCC have rarely been investigated and the studies have produced generally inconsistent results. Therefore, the outcomes of the studies are inadequate and unable to clearly demonstrate a direct correlation between cellular transformation and MCPyV. This review aims to present a comprehensive recapitulation of the available literature regarding the association of MCPyV with oncogenesis (MCC and non-MCC tumours).

The impact of merkel cell polyomavirus positivity on prognosis of merkel cell carcinoma: A systematic review and meta-analysis

Introduction

There are numerous findings over the past decade have indicated that Merkel cell carcinoma (MCC) may have two pathways of pathogenesis: one related to ultraviolet irradiation and the other to the Merkel cell polyomavirus (MCPyV). However, the predictive and clinicopathological value of MCPyV positivity in MCC patients is still debatable. This article aims to examine the most recent data regarding this issue.

Methods

The thorough literature searches were conducted in the Medline Ovid, PubMed, Web of Science, the Cochrane CENTRAL Databases, and Embase Databases until December 31, 2021. The associations between overall survival (OS), Merkel cell carcinoma-specific survival (MSS), recurrence-free survival (RFS), progression-free survival (PFS), clinicopathologic features, and MCPyV positivity were examined in our meta-analysis.

Results

This meta-analysis included a total of 14 studies involving 1595 patients. Our findings demonstrated a significant correlation between MCPyV positivity and improved OS (HR=0.61, 95%CI:0.39-0.94, P=0.026) and improved PFS (HR=0.61, 95% CI: 0.45-0.83, P=0.002). MCPyV positivity did not, however, appear to be associated with either MSS (HR=0.61, 95%CI: 0.28-1.32, P=0.209) or RFS (HR= 0.93, 95%CI: 0.37-2.34, P=0.873). Pooled results revealed a correlation between MCPyV positivity with gender (male vs. female, OR=0.606, 95%CI: 0.449-0.817, P=0.001), histopathological stage (AJCC I-II vs. III-IV, OR=1.636, 95%CI: 1.126-2.378, P=0.010) and primary site (head and neck vs. other sites, OR=0.409, 95%CI: 0.221-0.757, P=0.004).

Conclusion

These results imply that MCPyV positivity may present a promising predictive biomarker for human MCC and call for further study.

Application of immune enhanced organoids in modeling personalized Merkel cell carcinoma research

Merkel cell carcinoma (MCC) is a rare neuroendocrine cutaneous cancer, with incidence of less than 1/100,000, low survival rates and variable response to chemotherapy or immunotherapy. Herein we explore the application of patient tumor organoids (PTOs) in modeling personalized research in this rare malignancy. Unsorted and non-expanded MCC tumor cells were isolated from surgical specimens and suspended in an ECM based hydrogel, along with patient matched blood and lymph node tissue to generate immune enhanced organoids (iPTOs). Organoids were treated with chemotherapy or immunotherapy agents and efficacy was determined by post-treatment viability. Nine specimens from seven patients were recruited from December 2018-January 2022. Establishment rate was 88.8% (8/9) for PTOs and 77.8% (7/9) for iPTOs. Histology on matched patient tissues and PTOs demonstrated expression of MCC markers. Chemotherapy response was exhibited in 4/6 (66.6%) specimens with cisplatin and doxorubicin as the most effective agents (4/6 PTO sets) while immunotherapy was not effective in tested iPTO sets. Four specimens from two patients demonstrated resistance to pembrolizumab, correlating with the corresponding patient's treatment response. Routine establishment and immune enhancement of MCC PTOs is feasible directly from resected surgical specimens allowing for personalized research and exploration of treatment regimens in the preclinical setting.

Amyloid deposition with a granulomatous reaction in a resection specimen: A clue for a preexisting Merkel cell carcinoma

Merkel cell carcinoma (MCC) is an aggressive, highly metastatic, cutaneous neuroendocrine malignancy with poor prognosis. Here we describe a MCC excision specimen with a rare case of tumor-associated amyloid deposition in the absence of residual tumor cells. A 72-year-old man presented with a lesion of five- to six- months' duration on his left elbow, clinically thought to be a ganglion cyst. The biopsy specimen revealed a stage IIA MCC with classic histomorphologic and immunophenotypic findings, with tumor extending to the tissue edges. The patient underwent wide local excision with negative margins and a negative sentinel lymph node biopsy. Although the patient did not receive any presurgical chemotherapy, immunotherapy, or targeted therapy, the re-excision specimen showed only amphophilic, feathery deposits that were salmon-pink with Congo red stain and further confirmed as amyloid by electron microscopy; there were no residual carcinoma cells. Amyloid deposition in MCC has been described in rare case reports. Our case was extraordinary in that there was only amyloid deposition and an associated granulomatous reaction, without identifiable MCC cells. This case demonstrates that amyloid deposition may be evidence of a prior MCC at the site of a prior procedure and may warrant careful evaluation for residual MCC. This article is protected by copyright. All rights reserved.

Carcinoma de Merkel primario de la mama en un hombre con injerto cutáneo: reporte de caso

Introducción. El carcinoma de células de Merkel (CCM) es un cáncer neuroendocrino de la piel, agresivo, muy poco frecuente que, por lo general, aparece como un nódulo en la cara, cabeza o cuello. El CCM ocurre principalmente en adultos mayores. Presentación del caso. Hombre de 85 años, blanco, que asistió al Servicio de Mastología del Instituto Nacional de Oncología y Radiobiología (INOR), en La Habana, Cuba, por aumento de volumen, cambio de color y temperatura en la mama derecha. El paciente había sufrido trauma térmico en el hemitórax derecho 18 años antes de la consulta, el cual fue tratado mediante injerto cutáneo del muslo. En los estudios de imagen (ultrasonido, mamografía, resonancia magnética y tomografía computarizada) se observó un nódulo con características imagenológicas sugestivas de malignidad. El diagnóstico de CCM se confirmó mediante biopsia por punción con aguja gruesa, donde se reportó positividad de marcadores CD-56, CK-7 y Ki- 67. Conclusiones. Característicamente, el CCM se presenta como nódulos cutáneos firmes de rápido crecimiento en las áreas expuestas al sol, a diferencia del presente caso, en el que la lesión apareció en la piel injertada en el hemitórax derecho. Reconocer hallazgos imagenológicos sugestivos de esta neoplasia es de gran importancia para el diagnóstico en zonas inusuales del cuerpo como la mama.

Volumetric Modulated Arc Therapy Capabilities for Treating Lower-Extremity Skin Affected by Several Merkel Cell Carcinoma Nodules: When Technological Advances Effectively Achieve the Palliative Therapeutic Goal while Minimising the Risk of Potential Toxicities

The peculiar and rare clinical condition below clearly requires a customized care approach in the context of personalized medicine. An 80-year-old female patient who was subjected in 2018 to surgical removal of a cutaneous Merkel cell carcinoma (MCC) nodule located on the posterior surface of the left thigh and to three subsequent palliative radiotherapy treatments developed a fourth relapse in October 2020, with fifteen nodular metastases located in the left thigh and leg. Since the overall macroscopic disease was still exclusively regionally located and microscopic spread was likely extended also to clinically negative skin of the thigh and leg, we performed an irradiation of the whole left lower extremity. For this purpose the total target (65.5 cm) was divided into three sub-volumes. Dose prescription was 30 Gy in 15 daily fractions. A sequential boost of 10 Gy in 5 daily fractions was planned for macroscopic nodules. Plans were calculated by means of volumetric modulated arc therapy (VMAT) with the field overlap technique. Thanks to this, we obtained a homogeneous dose distribution in the field junction region; avoidance structures were delineated in the central part of the thigh and leg with the aim of achieving an optimal superficial dose painting and to reduce bone exposure to radiation. This case study demonstrates that VMAT allows for a good dose coverage for circumferential cutaneous targets while sparing deeper organs at risk. A reproducible image-guided set-up is fundamental for an accurate and safe dose delivery. However, local treatments such as radiotherapy for very advanced MCC of the lower extremities might have limited impact due to the high probability of systemic progression, as illustrated in this case. Radiation is confirmed as being effective in preventing MCC nodule progression toward skin wounding.

T-Cell Responses in Merkel Cell Carcinoma: Implications for Improved Immune Checkpoint Blockade and Other Therapeutic Options

Merkel cell carcinoma (MCC) is a rare and aggressive skin cancer with rising incidence and high mortality. Approximately 80% of the cases are caused by the human Merkel cell polyomavirus, while the remaining 20% are induced by UV light leading to mutations. The standard treatment of metastatic MCC is the use of anti-PD-1/-PD-L1-immune checkpoint inhibitors (ICI) such as Pembrolizumab or Avelumab, which in comparison with conventional chemotherapy show better overall response rates and longer duration of responses in patients. Nevertheless, 50% of the patients do not respond or develop ICI-induced, immune-related adverse events (irAEs), due to diverse mechanisms, such as down-regulation of MHC complexes or the induction of anti-inflammatory cytokines. Other immunotherapeutic options such as cytokines and pro-inflammatory agents or the use of therapeutic vaccination offer great ameliorations to ICI. Cytotoxic T-cells play a major role in the effectiveness of ICI, and tumour-infiltrating CD8⁺ T-cells and their phenotype contribute to the clinical outcome. This literature review presents a summary of current and future checkpoint inhibitor therapies in MCC and demonstrates alternative therapeutic options. Moreover, the importance of T-cell responses and their beneficial role in MCC treatment is discussed.