Expression of Mismatch Repair Proteins in Merkel Cell Carcinoma

Intratumoural and systemic inflammation as predictors for treatment response in BRAF-mutated melanoma patients under targeted therapies

Intratumoural as well as systemic inflammation in melanoma has thoroughly been studied in the context of patients treated with immune checkpoint inhibitors but not with BRAF/MEK inhibitors (BRAFi/MEKi). We aimed to study whether parameters of intratumoral and systemic inflammation correlate with clinical outcome in patients with BRAF-mutant metastatic melanoma treated with BRAFi/MEKi. We studied 51 CM patients with unresectable stage III or IV who had the indication for BRAFi/MEKi treatment based on confirmed BRAF mutation. Baseline systemic immune-inflammation markers such as the systemic immune-inflammation index (SII) and the expression of intratumoral inflammation markers such as COX-2 protein expression were correlated with clinical outcome measures. On multivariable analyses, lower intratumoral COX-2 expression (OR 33.9, 95% CI 3.2-356.8) and lower SII (OR 6.3, 95% CI 1.1-34.8) proved to be significant independent predictors for objective response to targeted therapy. Elevated S100B (HR 1.2, 95% CI 1.03-1.3) was a significant predictor for progressive disease. Moreover, elevated S100B (HR 1.37, 95% CI 1.14-1.65) and LDH (HR 1.002, 95% CI 1.0001-1.003) were significant independent predictors for melanoma-specific death. In conclusion, the present study indicates that low SII values and low intratumoral COX-2 protein expression are significant independent predictors for treatment response to BRAFi/MEKi.

An Updated Review of the Biomarkers of Response to Immune Checkpoint Inhibitors in Merkel Cell Carcinoma: Merkel Cell Carcinoma and Immunotherapy

Merkel cell carcinoma (MCC) is primarily a disease of the elderly Caucasian, with most cases occurring in individuals over 50. Immune checkpoint inhibitors (ICI) treatment has shown promising results in MCC patients. Although ~34% of MCC patients are expected to exhibit at least one of the predictive biomarkers (PD-L1, high tumor mutational burden/TMB-H/, and microsatellite instability), their clinical significance in MCC is not fully understood. PD-L1 expression has been variably described in MCC, but its predictive value has not been established yet. Our literature survey indicates conflicting results regarding the predictive value of TMB in ICI therapy for MCC. Avelumab therapy has shown promising results in Merkel cell polyomavirus (MCPyV)-negative MCC patients with TMB-H, while pembrolizumab therapy has shown better response in patients with low TMB. A study evaluating neoadjuvant nivolumab therapy found no significant difference in treatment response between the tumor etiologies and TMB levels. In addition to ICI therapy, other treatments that induce apoptosis, such as milademetan, have demonstrated positive responses in MCPyV-positive MCC, with few somatic mutations and wild-type TP53. This review summarizes current knowledge and discusses emerging and potentially predictive biomarkers for MCC therapy with ICI.

Expression of DNA mismatch repair proteins in melanoma patients treated with immune checkpoint inhibitors

PURPOSE

To investigate the protein expression of DNA mismatch repair (MMR) proteins in patients with cutaneous melanoma (CM) under immune checkpoint inhibitor (ICI) therapy.

METHODS

Immunohistochemistry was performed on tumor tissue for MMR proteins MLH1, MSH2, MSH6, and PMS2 in 50 metastatic CM patients treated with ICI (ipilimumab, nivolumab, pembrolizumab).

RESULTS

Best overall response (BOR) rate was 48% (24/50). Reduced MMR protein expression (nuclear expression in < 80% of tumor cells) was observed in 8 patients (16%). Compared to other clinical parameters, baseline neutrophil/lymphocyte ratio and reduced intratumoral MMR protein expression (P = 0.0033) were determined as the only parameters significantly associated with favorable BOR. However, in this small study population, reduced MMR protein expression did not reach statistical significance in multivariate analysis.

CONCLUSION

Reduced MMR protein expression is observed in CM and might predict favorable BOR in patients treated with ICI, as was observed for other entities. However, these findings need to be substantiated in larger patient cohorts.

Evolving Applications of Circulating Tumor DNA in Merkel Cell Carcinoma

Circulating tumor DNA (ctDNA) is a subset of circulating cell-free DNA released by lysed tumor cells that can be characterized by its shorter strand length and tumor genome-specific information. The relatively short half-life of ctDNA allows it to provide a real-time measure of tumor burden which has potential prognostic and surveillance value as a tumor biomarker. Merkel cell carcinoma (MCC) is a rare neuroendocrine skin cancer that requires close monitoring due to the high risk of relapse. There are currently no good tumor biomarkers for MCC patients, especially those who are negative for Merkel cell polyomavirus. ctDNA shows promise for improving the prognoses of MCC patients by monitoring tumor burden, identifying minimal residual disease (MRD), and stratifying patients by their likelihood of response to immune checkpoint inhibition or risk of relapse. In particular, bespoke ultra-sequencing platforms allow for the creation of patient-specific mutation panels that improve ctDNA detection, especially for patients with rare or uncharacteristic mutations. Leveraging bespoke ctDNA assays may improve physicians' ability to alter treatment plans for non-responsive or high-risk patients. In addition, ctDNA MRD monitoring may allow physicians to treat relapses early before clinically evident disease is present.

Merkel Cell Polyomavirus: Infection, Genome, Transcripts and Its Role in Development of Merkel Cell Carcinoma

The best characterized polyomavirus family member, i.e., simian virus 40 (SV40), can cause different tumors in hamsters and can transform murine and human cells in vitro. Hence, the SV40 contamination of millions of polio vaccine doses administered from 1955-1963 raised fears that this may cause increased tumor incidence in the vaccinated population. This is, however, not the case. Indeed, up to now, the only polyomavirus family member known to be the most important cause of a specific human tumor entity is Merkel cell polyomavirus (MCPyV) in Merkel cell carcinoma (MCC). MCC is a highly deadly form of skin cancer for which the cellular origin is still uncertain, and which appears as two clinically very similar but molecularly highly different variants. While approximately 80% of cases are found to be associated with MCPyV the remaining MCCs carry a high mutational load. Here, we present an overview of the multitude of molecular functions described for the MCPyV encoded oncoproteins and non-coding RNAs, present the available MCC mouse models and discuss the increasing evidence that both, virus-negative and -positive MCC constitute epithelial tumors.

Histopathologic Features for Overall Survival in Merkel Cell Carcinoma: A Case Series with Intact Mismatch Repair Protein Expression

OBJECTIVE

In a study of Merkel cell carcinoma (MCC), a fusion transcript between MLH1 and SPATA4 was identified. This fusion has the potential to generate the inactive or dominant-negative form of the protein. Therefore, we aimed to investigate whether mismatch repair protein deficiency occurr in MCC cases or not, in addition to the overall survival association with histopathologic features.

MATERIAL AND METHOD

A retrospective review of 15 patients diagnosed with a biopsy-proven Merkel Cell Carcinoma between 2012 and 2019 was performed. Mismatch repair (MMR) protein expressions were evaluated by immunohistochemistry.

RESULTS

The median follow-up time was 36 months (mean 41, range 2-103 months). Six (40%) patients died during follow-up. The overall survival (OS) at 1 year, 2 years, 3 years, and 5 years were 87%, 80%, 62%, and 53%, respectively. The patients diagnosed at < 60 years had an improved OS compared to those ≥60 years of age (p=0.016). Patients in clinical stage I had better OS than patients in clinical stage IV (p=0.011). Cases with pathological tumor stage (pT) 1 had better OS than pT3 and pT4 (p=0.045). Adjuvant radiotherapy or adjuvant radiotherapy+chemotherapy treatment improved OS compared to adjuvant chemotherapy (p=0.003). MMR protein nuclear expression was intact in 12 cases available for immunohistochemical study.

CONCLUSION

To the best of our knowledge, this is the second study that preferentially investigated the mismatch repair protein status of Merkel Cell Carcinoma. No mismatch repair protein deficiency of MCC cases was identified in the current study.

Protein expression of prognostic genes in primary melanoma and benign nevi

PURPOSE

To evaluate the protein expression characteristics of genes employed in a recently introduced prognostic gene expression assay for patients with cutaneous melanoma (CM).

METHODS

We studied 37 patients with CM and 10 with benign (melanocytic) nevi (BN). Immunohistochemistry of primary tumor tissue was performed for eight proteins: COL6A6, DCD, GBP4, KLHL41, KRT9, PIP, SCGB1D2, SCGB2A2.

RESULTS

The protein expression of most markers investigated was relatively low (e.g., DCD, KRT9, SCGB1D2) and predominantly cytoplasmatic in melanocytes and keratinocytes. COL6A6, GBP4, and KLHL41 expression was significantly enhanced in CM when compared to BN. DCD protein expression was significantly correlated with COL6A6, GBP4, and KLHL41. GBP4 was positively correlated with KLHL41 and inversely correlated with SCGB2B2. The latter was also inversely correlated with serum S100B levels at time of initial diagnosis. The presence of SCGB1D2 expression was significantly associated with ulceration of the primary tumor. KRT9 protein expression was significantly more likely found in acral lentiginous melanoma. The presence of DCD expression was less likely associated with superficial spreading melanoma subtype but significantly associated with non-progressive disease. The absence of SCGB2A2 expression was significantly more often observed in patients who did not progress to stage III or IV.

CONCLUSIONS

The expression levels observed were relatively low but differed in part with those found in BN. Even though we detected some significant correlations between the protein expression levels and clinical parameters (e.g., CM subtype, course of disease), there was no major concordance with the protective or risk-associated functions of the corresponding genes included in a recently introduced prognostic gene expression assay.

PMS2 Expression With Combination of PD-L1 and TILs for Predicting Survival of Esophageal Squamous Cell Carcinoma

Background

DNA mismatch repair (MMR) deficiency (dMMR) has been recognized as an important biomarker for immunotherapy in esophageal squamous cell carcinoma (ESCC), along with programmed death ligand 1 (PD-L1) expression and/or tumor-infiltrated lymphocytes (TILs). However, in ESCC, MMR protein assessment has not been well studied at present.

Methods

A total of 484 ESCC tissues treated between 2007 and 2010, in our hospital, were enrolled. Immunohistochemical expression of MLH1, MSH2, MSH6, PMS2, and PD-L1 on tissue microarray specimens and clinicopathological features, including TILs, were analyzed retrospectively.

Results

Out of the 484 studied cases, loss of MLH1, MSH2, MSH6, and PMS2 expression were found in 6.8%, 2.1%, 8.7%, and 4.8% patients, respectively. dMMR was found in 65 patients, 37 cases involved in one MMR protein, 17 cases involved in two proteins, 7 cases involved in three proteins, and 4 cases involved in four proteins. There was no significant survival difference between pMMR (MMR-proficient) and dMMR patients (P>0.05). However, 224 patients with low PMS2 expression had better DFS and OS than 260 patients with high PMS2 expression (P=0.006 for DFS and 0.008 for OS), which was identified as an independent prognostic factor in multivariate analyses. Positive PD-L1 expression was detected in 341 (70.5%) samples. In stage I-II disease, patients with PD-L1 expression had better DFS and OS than those without PD-L1 expression(P<0.05), which was not found in stage III-IV disease. With the ITWG system, 40.1% of cases were classified as high TILs. Patients in the high-TILs group tended to have better DFS (P=0.055) and OS (P=0.070) than those in the low-TILs group and the differences were statistically significant in pMMR, high MSH6, or PMS2 expression cases (P<0.05). Also, high PMS2 expression patients with both PD-L1 expression and high TILs, had similar DFS and OS compared with low PMS2 expression patients (P>0.05), which were much better than other high PMS2 expression patients.

Conclusion

The expression level of MMR proteins could also be used as a prognostic factor in ESCC and PMS2 expression outperformed other MMR proteins for predicting survival. The combination of PD-L1 expression and TILs may lead to more efficient risk stratification of ESCC.

Detection of MSH2 Gene Methylation in Extramammary Paget's Disease by Methylation-Sensitive High-Resolution Melting Analysis

Background

Extramammary Paget's disease (EMPD) is a rare skin tumor. Hypermethylation in the MSH2 promoter resulting in the downregulation of its protein expression shows a high detection rate in EMPD tumor tissue, which indicates that the methylation of MSH2 may play an important role in the pathogenesis of EMPD.

Objective

This study aims to establish a rapid analysis strategy based on the methylation-sensitive high-resolution melting curve (MS-HRM) to detect the methylation level of the MSH2 promoter.

Methods

With the use of universal methylated human DNA products, we established the MS-HRM standard curve to quantitatively detect the methylation level of the MSH2 promoter. Then, all 57 EMPD tumor DNA samples were analyzed. Pyrosequencing assay was also carried out to test the accuracy and efficacy of MS-HRM. Besides, a total of 54 human normal and other cancerous tissues were included in this study to test the reliability and versatility of the MS-HRM standard curve.

Results

In this study, by using the established MS-HRM, we found that 96.5% (55/57) EMPD tumor samples had varying methylation levels in the MSH2 promoter ranging from 0% to 30%. Then, the methylation data were compared to the results obtained from pyrosequencing, which showed a high correlation between these two techniques by Pearson's correlation (r = 0.9425) and Bland–Altman plots (mean difference = −0.1069) indicating that the methylation levels analyzed by MS-HRM were consistent with DNA pyrosequencing. Furthermore, in 23 normal and 31 other cancerous tissue samples, there were two colorectal cancer (CRC) tissues that tested MSH2 methylation positive (1% and 5%) which confirmed that our established MS-HRM can be widely applied to various types of samples.

Conclusion

MS-HRM standard curve can be used for the detection of the methylation level of MSH2 in EMPD tumor samples and other cancerous tissues potentially, which presents a promising candidate as a quantitative assay to analyze MSH2 promoter methylation in routine pathological procedure.

Mismatch Repair Protein Expression and Microsatellite Instability in Cutaneous Squamous Cell Carcinoma

There exist relatively sparse and conflicting data on high-level microsatellite instability (MSI-H) and deficient mismatch repair (dMMR) in cutaneous malignancies. We aimed to determine the expression profiles of MMR proteins (MSH2, MSH6, MLH1, and PMS2) in different progression stages of cutaneous squamous cell carcinoma (cSCC, 102 patients in total) by immunohistochemistry, and search for MSI-H in patients with low-level MMR or dMMR using multiplex-PCR. Low-level MMR protein expression was observed in five patients: One patient with primary cSCC < 2 mm thickness and low-level MLH1, three patients with primary cSCC > 6 mm (including one with low-level MSH2, as well as MSH6 expression, and two with low-level PMS2), and one patient with a cSCC metastasis showing low-level MSH2 as well as MSH6. Intergroup protein expression analysis revealed that MLH1 and MSH2 expression in actinic keratosis was significantly decreased when compared to Bowen’s disease, cSCC < 2 mm, cSCC > 6 mm, and cSCC metastasis. In cases with low-level MMR, we performed MSI-H tests revealing three cases with MSI-H and one with low-level MSI-L. We found low-level MMR expression in a small subset of patients with invasive or metastatic cSCC. Hence, loss of MMR expression may be associated with tumour progression in a small subgroup of patients with non-melanoma skin cancer.