A study of apoptosis in Merkel cell carcinoma: an immunohistochemical, ultrastructural, DNA ladder, and TUNEL labeling study

The HDAC inhibitor domatinostat induces type I interferon α in Merkel cell carcinoma by HES1 repression

BACKGROUND

Class I selective histone deacetylase inhibitors (HDACi) have been previously demonstrated to not only increase major histocompatibility complex class I surface expression in Merkel cell carcinoma (MCC) cells by restoring the antigen processing and presentation machinery, but also exert anti-tumoral effect by inducing apoptosis. Both phenomena could be due to induction of type I interferons (IFN), as has been described for HDACi. However, the mechanism of IFN induction under HDACi is not fully understood because the expression of IFNs is regulated by both activating and inhibitory signaling pathways. Our own preliminary observations suggest that this may be caused by suppression of HES1.

METHODS

The effect of the class I selective HDACi domatinostat and IFNα on cell viability and the apoptosis of MCPyV-positive (WaGa, MKL-1) and -negative (UM-MCC 34) MCC cell lines, as well as, primary fibroblasts were assessed by colorimetric methods or measuring mitochondrial membrane potential and intracellular caspase-3/7, respectively. Next, the impact of domatinostat on IFNA and HES1 mRNA expression was measured by RT-qPCR; intracellular IFNα production was detected by flow cytometry. To confirm that the expression of IFNα induced by HDACi was due to the suppression of HES1, it was silenced by RNA interference and then mRNA expression of IFNA and IFN-stimulated genes was assessed.

RESULTS

Our studies show that the previously reported reduction in viability of MCC cell lines after inhibition of HDAC by domatinostat is accompanied by an increase in IFNα expression, both of mRNA and at the protein level. We confirmed that treatment of MCC cells with external IFNα inhibited their proliferation and induced apoptosis. Re-analysis of existing single-cell RNA sequencing data indicated that induction of IFNα by domatinostat occurs through repression of HES1, a transcriptional inhibitor of IFNA; this was confirmed by RT-qPCR. Finally, siRNA-mediated silencing of HES1 in the MCC cell line WaGa not only increased mRNA expression of IFNA and IFN-stimulated genes but also decreased cell viability.

CONCLUSION

Our results demonstrate that the direct anti-tumor effect of HDACi domatinostat on MCC cells is at least in part mediated via decreased HES1 expression allowing the induction of IFNα, which in turn causes apoptosis.

Regressed Seminoma with Metastases to the Jejunum and Retroperitoneum

A 66-year-old man with vomiting and weight loss was referred to our hospital. Abdominal computed tomography showed small bowel obstruction caused by a presumed small intestinal tumor. Single-balloon endoscopy showed an ulcerated tumor and marked stenosis of the jejunum. Immunohistochemical staining suggested the tumor to be poorly differentiated or undifferentiated carcinoma. The patient underwent open surgical resection of the jejunal tumor and regional lymph nodes both to improve the quality of life of the patient and to possibly get a cure of the presumed jejunal carcinoma. Pathological examination of the excised tumor and lymph nodes including para-aortic lymph nodes showed large-sized tumor cells and massive lymphocyte infiltrates. Immunostaining showed the tumor cells to be OCT3/4, AE1/AE3, CD117, and D2-40 positive, leading to the diagnosis of metastatic seminoma. With the preoperative diagnosis of a presumed burned-out tumor of the testis, the patient underwent left high orchiectomy. Pathological examination of the left testis showed marked scar tissue, no teratoma elements, and no residual tumor cells. Under the final diagnosis of regressed seminoma, the patient has received combination chemotherapy using bleomycin, etoposide, and cisplatin as adjuvant chemotherapy. Surgical oncologists should take regressed seminoma into their differential diagnosis when the biopsy specimens of the presumed intestinal malignancy show poorly differentiated or undifferentiated atypical cells with massive lymphocyte infiltrates, especially in postpubertal men. Confirmation of a malignant noninvasive component should be another important clue to the appropriate differential diagnosis when choosing between metastatic seminoma and poorly differentiated or undifferentiated intestinal primary malignancies.

Exploring the Prognostic Role of Ki67 Proliferative Index in Merkel Cell Carcinoma of the Skin: Clinico-Pathologic Analysis of 84 Cases and Review of the Literature

The exact prediction of outcome of patients with Merkel cell carcinoma (MCC) of the skin is difficult to determine, although several attempts have been made to identify clinico-pathologic prognostic factors. The Ki67 proliferative index is a well-known marker routinely used to define the prognosis of patients with neuroendocrine neoplasms. However, its prognostic value has been poorly investigated in MCC, and available published results are often contradictory mainly because restricted to small series in the absence of standardized methods for Ki67 evaluation. For this reason, we explored the potential prognostic role of Ki67 proliferative index in a large series of MCCs using the WHO standardized method of counting positive cells in at least 500 tumor cells in hot spot areas on camera-captured printed images. In addition, since MCC may be considered as the cutaneous counterpart of digestive neuroendocrine carcinomas (NECs), we decided to stratify MCCs using the available and efficient Ki67 threshold of 55%, which was found prognostic in digestive NECs. This choice was also supported by the Youden index analysis. In addition, we analyzed the prognostic value of other clinico-pathologic parameters using both univariate and multivariate analysis. Ki67 index appeared significantly associated with prognosis at univariate analysis together with stage IV, lack of MCPyV, and p63 expression, but not at the multivariate analysis, where survival resulted independently influenced by p63 expression and tumor stage, only.

MicroRNAs as Potential Biomarkers in Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is a rare and aggressive type of skin cancer associated with a poor prognosis. This carcinoma was named after its presumed cell of origin, the Merkel cell, which is a mechanoreceptor cell located in the basal epidermal layer of the skin. Merkel cell polyomavirus seems to be the major causal factor for MCC because approximately 80% of all MCCs are positive for viral DNAs. UV exposure is the predominant etiological factor for virus-negative MCCs. Intracellular microRNA analysis between virus-positive and virus-negative MCC cell lines and tumor samples have identified differentially expressed microRNAs. Comparative microRNA profiling has also been performed between MCCs and other non-MCC tumors, but not between normal Merkel cells and malignant Merkel cells. Finally, Merkel cell polyomavirus encodes one microRNA, but its expression in virus-positive MCCs is low, or non-detectable or absent, jeopardizing its biological relevance in tumorigenesis. Here, we review the results of microRNA studies in MCCs and discuss the potential application of microRNAs as biomarkers for the diagnosis, progression and prognosis, and treatment of MCC.

Merkel cell carcinoma. Case report

BACKGROUND

Merkel cell carcinoma (MCC) is a rare aggressive skin tumour affecting mainly older and immuno suppressed individuals (see our review on MCC in this volume).

AIM

This is a case report describing our first experience with Merkel cell carcinoma in an elderly woman on chemo therapy for lymphoma and it covers the diagnosis, treatment and outcome.

METHODS

We did a radical excision of the soft tissue in the tumor area in conjunction with total paroditectomy and resection of the body of the zygomatic bone by radical block neck dissection. The skin defect was reconstructed myocutaneous free flap by a plastic surgeon.

RESULTS AND CONCLUSION

At 12 months follow-up, the MCC had not recurred.

Diagnostic biopsy does not commonly induce intratumoral CD8 T cell infiltration in Merkel cell carcinoma

Background

Merkel cell carcinoma is a polyomavirus-associated cancer that is strongly linked with T lymphocyte immune suppression in epidemiologic studies. CD8+ T cell infiltration into MCC tumors (intratumoral) has recently been shown to be strongly predictive of improved survival. In contrast, the presence of CD8+ T cells at the border of the tumor (peritumoral) had no independent prognostic value. Spontaneous regression has been reported for MCC approximately one thousand times more often than would be expected given the frequency of this cancer. Many of these events began shortly after biopsy, and in some cases lymphocytic infiltration was described.

Methodology/Principal Findings

To determine whether CD8+ lymphocyte infiltration in MCC tumors is commonly altered by biopsy.33 MCC patients who had microscopic confirmation of MCC on both an initial biopsy and a re-excision specimen were included in this study. Intratumoral and peritumoral CD8 lymphocyte infiltration was quantitated using immunohistochemistry and compared using the paired t-test in biopsy versus re-excision samples. There was a trend toward increased CD8 infiltration after biopsy in a peritumoral (‘stalled’) pattern (p = 0.08), however, biopsy was not associated with a significant increase in CD8 T cells in the clinically more important intratumoral location (p = 0.58).

Conclusions/Significance

The initial diagnostic biopsy for MCC does not commonly alter intratumoral CD8+ T cell infiltration, suggesting it does not directly induce immunologic recognition of this cancer. Because CD8 infiltration is typically stable after biopsy, this parameter may be useful to assess the efficacy of future immune therapies for this virus-associated, immunogenic, often-lethal cancer.

Merkel cell carcinoma. A review

BACKGROUND

Merkel cell carcinoma (MCC) is a rare potentially fatal skin tumour affecting older mainly white people and younger immunosuppressed individuals. While uncommon, the incidence is increasing relative to melanoma and with twice the lethality. The benign appearance of the tumour usually on exposed skin parts, contrasting with its extensive microscopic invasion, can delay timely diagnosis. Recurrent MCC is currently attributed to the recently discovered Merkel cell polyomavirus This brief review of MCC covers the history, epidemiology,etiology,clinical and histological features, treatment and prognosis.

METHODS

Literature search using PubMed and search words Merkel cell carcinoma (MCC), etiology, treatment for the years 1972 to 2010.

RESULTS AND CONCLUSION

Merkel cell carcinoma is a rare malignancy with uncertain prognosis. Due to the uncommon occurrence and dearth of randomized studies, there is no agreement on optimal treatment. The tumor has only recently been included in the international classification of tumors (NCCN). The treatment approaches found to be best are radical surgery of primary tumor, drainage of lymph node extension and possibly adjuvant loco-regional radiotherapy. The basis of successful treatment however, remains prevention regular dermatological examination in immunosuppressed patients and early initiation of combination therapy, based on radical surgery supplemented by radiotherapy and palliative chemotherapy in the last resort.

Type I and II IFNs inhibit Merkel cell carcinoma via modulation of the Merkel cell polyomavirus T antigens

Merkel cell carcinoma (MCC) is a rare and highly aggressive skin cancer associated with the Merkel cell polyomavirus (MCV). As MCC cell lines show oncogene addiction to the MCV T antigens, pharmacologic interference of the large T antigen (LTA) may represent an effective therapeutic approach for this deadly cancer. In this study, we investigated the effects of IFNs on MCC cell lines, especially on MCV-positive (MCV(+)) lines. Type I IFNs (i.e., Multiferon, a mix of different IFN-α subtypes, and IFN-β) strongly inhibited the cellular viability. Cell-cycle analysis showed increased sub-G fractions for these cells upon IFN treatment indicating apoptotic cell death; these effects were less pronounced for IFN-γ. Notably, this inhibitory effect of type I IFNs on MCV(+) MCC cell lines was associated with a reduced expression of the MCV LTA as well as an increased expression of promyelocytic leukemia (PML) protein, which is known to interfere with the function of the LTA. In addition, the intratumoral application of Multiferon resulted in a regression of MCV(+) but not MCV(-) MCCs in vivo. Together, our findings show that type I IFNs have a strong antitumor effect, which is at least in part explained by modulation of the virally encoded LTA.

Hematoporphyrin monomethyl ether enhances the killing action of ultrasound on osteosarcoma in vivo

OBJECTIVES

Osteosarcoma is one of the most common malignant cancers afflicting young adults. Ultrasound is a new therapeutic modality for controlling malignant cancers. Enhancing the efficacy of ultrasound treatment will improve clinical outcomes. The aim of this study was to investigate the killing action of ultrasound on osteosarcoma enhanced by hematoporphyrin monomethyl ether (HMME) in vivo.

METHODS

An animal model of an osteosarcoma xenograft was set up to investigate the inhibitory effect of sonoactivating HMME on osteosarcoma. High-performance liquid chromatography was used to analyze the time course of HMME in the osteosarcoma xenograft. Three hours after intravenous (IV) administration of HMME, ultrasound radiation was administered in the osteosarcoma xenograft. On day 7 after ultrasound radiation, the tumor volume and weight were measured and calculated for effect assessment, hematoxylin-eosin staining for histopathologic examination, immunohistochemical staining for proliferating cell nuclear antigen (PCNA) expression, and terminal deoxyuridine nick end-labeling (TUNEL) staining for apoptosis examinations.

RESULTS

The peak value of HMME in osteosarcoma tissues increased with time after IV administration of HMME and reached a plateau at 3 hours. The increasing rates of the tumor volume and weight in the control group were very fast, but the increasing rates in the ultrasound-alone group were slower, and those in the ultrasound-HMME group were the slowest throughout the observation period. There was a significant difference between the HMME-ultrasound, ultrasound-alone, and control groups (P < .01). Hematoxylin-eosin staining showed that some cells had typical cell death such as pyknosis and nuclear fragmentation after ultrasound radiation alone. More cells with pyknosis, nuclear fragmentation, and even karyolysis were found after HMME-ultrasound treatment. Immunohistochemical staining showed that the percentage of PCNA-positive cells decreased and that of TUNEL-positive cells increased after ultrasound treatment alone, and the changes in the PCNA- and TUNEL-positive percentages were significantly enhanced by pretreatment with HMME (20 mg/kg, IV) for 3 hours and ultrasound radiation (10.5 MHz) for 120 seconds at an intensity of 0.8 W/cm(2) (P < .05).

CONCLUSIONS

Hematoporphyrin monomethyl ether pretreatment could substantially enhance the growth inhibition of ultrasound on osteosarcoma, which suggests that HMME is an efficient sonosensitizer, and ultrasound radiation with HMME could be developed as a new modality for treating osteosarcoma.

Complete spontaneous regression in Merkel cell carcinoma

Merkel cell carcinoma is a rare, aggressive, cutaneous malignancy of the elderly with a generally poor prognosis. Like all skin cancers, its incidence is rising. A few reports of spontaneous regression have been published. The case of a 67-year-old female patient who presented with a cheek Merkel cell carcinoma is described. Following biopsy it underwent complete regression with no evidence of residual tumour in the excision specimen taken seven weeks later. The current knowledge of Merkel cell carcinoma and the other cases of spontaneous regression described in the literature are reviewed.

Differential kinetic features by tumour topography in cutaneous small-cell neuroendocrine (Merkel cell) carcinomas

BACKGROUND/OBJECTIVES

Merkel cell carcinomas (MCC) reveal epithelial and neuroendocrine differentiation, but its topographic cell kinetics remains unknown. This study analyses proliferation, apoptosis, and DNA ploidy by topography, features that can help planning therapeutic protocols. This study topographically analyses proliferation, apoptosis, and DNA ploidy.

METHODS

We selected 27 small-cell MCCs (expressing one epithelial and two neural markers, with consistent ultrastructural findings) to evaluate mitotic figure counting, Ki-67 index, apoptosis index based on the in situ end labelling of fragmented DNA (using Escherichia coli DNA polymerase I, Klenow fragment), DNA ploidy, and BCL2 and TP53 immuno-expression. At least 50 high-power fields were screened per topographic compartment (superficial or papillary dermis, and deep or reticular dermis), recording average and standard deviation for each variable. Variables were statistically compared in each tumour compartment using analysis of variance and Student's t-test (significant if P < 0.05).

RESULTS

MCCs revealed superficial aneuploid DNA content, and no topographic differences for proliferation markers. Apoptosis showed significantly lower values in the deep compartment (average, P = 0.0050, and standard deviation, P = 0.0074), correlating with increased BCL2 and TP53 immuno-expressions.

CONCLUSIONS

High homogeneously distributed proliferation and superficial aneuploid DNA content defines MCCs. Apoptosis follows proliferation in superficial compartments, being less variable and proliferation independent in deep compartments, where it is inversely correlated with BCL2/TP53 expression.

Immunohistochemical distinction between merkel cell carcinoma and small cell carcinoma of the lung

We assessed the usefulness of several immunohistochemical stains in distinguishing these two neoplasms, including cytokeratin 7, cytokeratin 20 (CK20), neuron-specific enolase, chromogranin, synaptophysin, neurofilaments (NF), thyroid-transcription factor-1 (TTF-1), CD56 antigen, S-100 protein, vimentin, c-erbB-2 oncoprotein, and CD117 antigen. All 13 cases of Merkel cell carcinoma evaluated were positive for CK20, and negative for TTF-1. Twelve of 13 Merkel cell carcinoma cases were positive for NF. Eleven of 13 cases of small cell lung carcinoma were positive for TTF-1. All small cell lung carcinoma cases were negative for NF, and all but one were negative for CK20. In terms of the remaining antigens, there were no differences of significance between the two neoplasms. These findings suggest that a set of three immunohistochemical stains, including CK20, NF, and TTF-1, is useful in affording a distinction between Merkel cell carcinoma and small cell lung carcinoma.

Merkel cell carcinoma

Background

Merkel cell carcinoma (MCC) is an unusual primary neuroendocrine carcinoma of the skin. MCC is a fatal disease, and patients have a poor chance of survival. Moreover, MCC lacks distinguishing clinical features, and thus by the time the diagnosis is made, the tumour usually have metastasized. MCC mainly affects sun-exposed areas of elderly persons. Half of the tumours are located in the head and neck region.

Methods

MCC was first described in 1972. Since then, most of the cases reported, have been in small series of patients. Most of the reports concern single cases or epidemiological studies. The present study reviews the world literature on MCC. The purpose of this article is to shed light on this unknown neuroendocrine carcinoma and provide the latest information on prognostic markers and treatment options.

Results

The epidemiological studies have revealed that large tumour size, male sex, truncal site, nodal/distant disease at presentation, and duration of disease before presentation, are poor prognostic factors. The recommended initial treatment is extensive local excision. Adjuvant radiation therapy has recently been shown to improve survival. Thus far, no chemotherapy protocol have achieved the same objective.

Conclusion

Although rare, the fatality of this malignancy makes is important to understand the etiology and pathophysiology. During the last few years, the research on MCC has produced prognostic markers, which can be translated into clinical patient care.

The effect of aloe emodin on the proliferation of a new merkel carcinoma cell line

A free-floating cell line has been established from a metastatic lesion of a Merkel cell carcinoma (MCC) patient. The cell line was characterized by immunocytochemical reactions with antibodies against the epithelial and neuroendocrine antigens: cytokeratin 20, neuron-specific enolase, chromogranin A, neurofilament protein, synaptophysin, and calcitonin. Karyotype analysis of the MCC cells showed deletion in chromosomes 3 and 7, loss of chromosome 10, and several translocations in other chromosomes. No mutation was detected in the TP53 gene, after analyzing the complete coding region. Growth factors such as basic fibroblast growth factor, transforming growth factor-beta, and nerve and epidermal growth factors had no effect on the proliferation of the cells. The differentiation-inducing agents sodium butyrate and dimethyl sulfoxide, especially the former, markedly inhibited the proliferation of the MCC cells. Aloe emodin, a natural constituent of aloe vera leaves, significantly inhibited the growth of MCC cells. Aloe emodin has been reported to be nontoxic for normal cells but to possess specific toxicity for neuroectodermal tumor cells. Differentiation-inducing agents, and aloe emodin, merit further investigation as potential agents for treating MCC.