Virus-negative Tumors Research Articles

Distinct Regulation of EZH2 and its Repressive H3K27me3 Mark in Polyomavirus-Positive and -Negative Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is an aggressive skin cancer for which Merkel cell polyomavirus integration and expression of viral oncogenes small T and Large T have been identified as major oncogenic determinants. Recently, a component of the PRC2 complex, the histone methyltransferase enhancer of zeste homolog 2 (EZH2) that induces H3K27 trimethylation as a repressive mark has been proposed as a potential therapeutic target in MCC. Because divergent results have been reported for the levels of EZH2 and trimethylation of lysine 27 on histone 3, we analyzed these factors in a large MCC cohort to identify the molecular determinants of EZH2 activity in MCC and to establish MCC cell lines' sensitivity to EZH2 inhibitors. Immunohistochemical expression of EZH2 was observed in 92% of MCC tumors (156 of 170), with higher expression levels in virus-positive than virus-negative tumors (P= 0.026). For the latter, we showed overexpression of EZHIP, a negative regulator of the PRC2 complex. Invitro, ectopic expression of the large T antigen in fibroblasts led to the induction of EZH2 expression, whereas the knockdown of T antigens in MCC cell lines resulted in decreased EZH2 expression. EZH2 inhibition led to selective cytotoxicity on virus-positive MCC cell lines. This study highlights the distinct mechanisms of EZH2 induction between virus-negative and -positive MCC.

Hit and run oncogeneses in head and neck cancers requires greater investigation.

Head and neck cancers are unique in so far that twomajor oncogenic viruses, Epstein Barr virus(EBV) and Human papillomavirus(HPV) infect adjacent anatomy and cause nasopharyngeal and oropharyngeal cancers, respectively. Dominant recognized carcinogens are alcohol and tobacco but some head and neck cancers have been found to have mixed carcinogens (including betel leaf, areca nuts, slaked lime, viruses, etc.) involved in their oncogenesis and conversely, groups of patients with unknown or less dominant carcinogens involved in their development. These cancers may have had viral involvement in the past but then lost most of their viral nucleic acids (be they DNA and/or RNA) below a detection threshold, thus rendering them virus-negative. Some of these virus-negative tumors appear to have mutagenic signatures associated with virus-positive cancers, for example, from the APOBEC defense mechanism which is known to mutate viral nucleic acids as well as cause collateral damage to host DNA, with subsequent development of strongly viral prejudiced mutational signatures. These mechanisms are likely to be less efficient at oncogenesis than traditional EBV and HPV oncogenes directly driving mutagenesis, thus accounting for the smaller frequencies of these cancers found. More profound investigations of these unusual tumors are warranted to dissect out these mechanistic pathways.

Merkel Cell Carcinoma of Unknown Primary: Immunohistochemical and Molecular Analyses Reveal Distinct UV-Signature/MCPyV-Negative and High Immunogenicity/MCPyV-Positive Profiles.

Simple SummaryMerkel cell carcinomas (MCCs) of unknown primary are defined as deep-seated tumors without an associated cutaneous tumor. Although the distinction has important clinical implications, it remains unclear whether these tumors represent primary tumors of lymph nodes or metastatic cutaneous primaries. We compared the immunohistochemical profiles of four groups of Merkel cell carcinomas (virus-positive and virus-negative unknown primary tumors and virus-positive and virus-negative cutaneous tumors) and performed molecular studies on the unknown primary tumors. Virus-positive and virus-negative Merkel cell carcinomas of unknown primary (MCC-UPs) exhibited an immunoprofile similar to virus-positive and virus-negative primary cutaneous MCCs, respectively. Similar to primary cutaneous Merkel cell carcinomas, virus-negative unknown primary tumors exhibited UV signatures and frequent high tumor mutational burdens, whereas few molecular alterations were noted in virus-positive tumors. Although additional studies are warranted for the virus-positive cases, our findings are supportive of a cutaneous metastatic origin for virus-negative Merkel cell carcinomas of unknown primary.Background: Merkel cell carcinomas of unknown primary (MCC-UPs) are defined as deep-seated tumors without an associated cutaneous tumor. Although the distinction has important clinical implications, it remains unclear whether these tumors represent primary tumors of lymph nodes or metastatic cutaneous primaries. Methods: We compared the immunohistochemical profiles of four groups of MCCs (Merkel cell polyomavirus (MCPyV)-positive UP, MCPyV-negative UP, MCPyV-positive known primary (KP), and MCPyV-negative KP) using B-cell and pre-B-cell markers, cell cycle regulating proteins, follicular stem cell markers, and immune markers, and performed next generation and Sanger sequencing. Results: Virus-positive and virus-negative MCC-UPs exhibited an immunoprofile similar to virus-positive and virus-negative primary cutaneous MCCs, respectively. MCC-UP tumors (both virus-positive and -negative) were immunogenic with similar or even higher tumoral PD-L1 expression and intratumoral CD8 and FoxP3 infiltrates in comparison to MCPyV-positive cutaneous tumors. In addition, similar to primary cutaneous MCCs, MCPyV-negative MCC-UPs exhibited UV signatures and frequent high tumor mutational burdens, whereas few molecular alterations were noted in MCPyV-positive MCC-UPs. Conclusions: Our results showed distinct UV-signatures in MCPyV-negative tumors and high immunogenicity in MCPyV-positive tumors. Although additional studies are warranted for the MCPyV-positive cases, our findings are supportive of a cutaneous metastatic origin for MCPyV-negative MCC-UP tumors.

582 The discovery of new therapeutic combinations for Merkel cell carcinoma by small-molecule synergy screening

Merkel cell carcinoma (MCC) is a rare and highly metastatic neuroendocrine skin cancer. The majority of MCC tumors are virus positive (VP-MCC) and are associated with integrated Merkel cell polyomavirus, whereas the remainder of MCC are virus-negative (VN-MCC) tumors that are characterized by ultraviolet light associated mutations. Metastatic MCC is treated by immunotherapy or chemotherapy. Conventional chemotherapy is usually unbeneficial in MCC, and although immune checkpoint inhibitor (ICI) therapy can be effective, it is contraindicated in many patients and others have disease progression despite immunotherapy.

Abstract IA11: Bladder cancers affecting transplant recipients harbor diverse viruses that associate with overall survival

Abstract BK polyomavirus (BKPyV) is a ubiquitous virus that establishes a lifelong subclinical infection in the urinary tract. In transplant recipients, BKPyV can reactivate and cause kidney and bladder damage. Recent sequencing studies of tumors from transplant recipients have revealed that BKPyV sequences are present in approximately 25% of bladder tumors. This is dramatically higher than the <1% rate of BKPyV detection observed in muscle-invasive bladder cancers affecting the general population. Like cancer-causing human papillomaviruses (HPVs), BKPyV has been shown to upregulate the human cytosine deaminase APOBEC3B, which has emerged as the second most abundant source of point mutations in human cancers. Furthermore, the APOBEC3-associated mutation signature is the most abundant mutational signature in bladder cancer. To comprehensively assess the role of BKPyV and other viruses in bladder cancer from solid organ transplant recipients, we used a database linking US transplant and cancer registries to identify and collect 44 archived primary bladder tumors, 5 metastases, and 15 adjacent normal tissue specimens. Whole-genome and total RNA sequencing was performed on the samples. From these data, we detected BKPyV in 18% of primary tumors. In five cases, there is clear evidence of BKPyV integration into the host cell genome, and all cases show transcription of the viral tumor antigens. In a separate set of analyses, BKPyV transcription was detected in 3.7% of non-muscle-invasive early-stage bladder cancer cases affecting the general population. Our surveys also detected other viruses, including high- and low-risk HPVs, JC polyomavirus (JCPyV), and anelloviruses, at lower frequencies. Two primary-metastatic pairs maintained clonally integrated HPV or BKPyV and respective viral oncogene expression in the metastatic lesions. Nearly all tumors had dominant APOBEC3 signature mutations, and BKPyV-positive tumors expressed significantly more APOBEC3B compared to virus-negative tumors or normal tissues. Tumors from four kidney transplant patients showed high mutation burden consistent with exposure to aristolochic acid, a nephrotoxic carcinogen found in some herbal supplements. Clinical data indicate that BKPyV-positive tumors are predominantly high grade with invasive behavior. Strikingly, survival was significantly shorter for patients whose tumors harbored BKPyV or JCPyV (9.7 and 8.4 months, respectively) compared to patients with tumors harboring HPV or no detectable viruses (65.8 and 50.2 months, respectively). This study comprehensively characterizes the genomes and transcriptomes of tumors, revealing several distinct tumor etiologies that impact patient outcome. Citation Format: Gabriel J. Starrett, Kelly Yu, David Petersen, Petra Lenz, Lars Dyrskjøt, Paul Meltzer, Eric Engels, Christopher B. Buck. Bladder cancers affecting transplant recipients harbor diverse viruses that associate with overall survival [abstract]. In: Proceedings of the AACR Special Conference on the Microbiome, Viruses, and Cancer; 2020 Feb 21-24; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2020;80(8 Suppl):Abstract nr IA11.

Clinical and molecular characterization of virus-positive and virus-negative Merkel cell carcinoma

BackgroundMerkel cell carcinoma (MCC) is a highly aggressive neuroendocrine carcinoma of the skin caused by either the integration of Merkel cell polyomavirus (MCPyV) and expression of viral T antigens or by ultraviolet-induced damage to the tumor genome from excessive sunlight exposure. An increasing number of deep sequencing studies of MCC have identified significant differences between the number and types of point mutations, copy number alterations, and structural variants between virus-positive and virus-negative tumors. However, it has been challenging to reliably distinguish between virus positive and UV damaged MCC.MethodsIn this study, we assembled a cohort of 71 MCC patients and performed deep sequencing with OncoPanel, a clinically implemented, next-generation sequencing assay targeting over 400 cancer-associated genes. To improve the accuracy and sensitivity for virus detection compared to traditional PCR and IHC methods, we developed a hybrid capture baitset against the entire MCPyV genome and software to detect integration sites and structure.ResultsSequencing from this approach revealed distinct integration junctions in the tumor genome and generated assemblies that strongly support a model of microhomology-initiated hybrid, virus-host, circular DNA intermediate that promotes focal amplification of host and viral DNA. Using the clear delineation between virus-positive and virus-negative tumors from this method, we identified recurrent somatic alterations common across MCC and alterations specific to each class of tumor, associated with differences in overall survival. Finally, comparing the molecular and clinical data from these patients revealed a surprising association of immunosuppression with virus-negative MCC and significantly shortened overall survival.ConclusionsThese results demonstrate the value of high-confidence virus detection for identifying molecular mechanisms of UV and viral oncogenesis in MCC. Furthermore, integrating these data with clinical data revealed features that could impact patient outcome and improve our understanding of MCC risk factors.

Distinct Biological Types of Ocular Adnexal Sebaceous Carcinoma: HPV-Driven and Virus-Negative Tumors Arise through Nonoverlapping Molecular-Genetic Alterations

Ocular adnexal (OA) sebaceous carcinoma is an aggressive malignancy of the eyelid and ocular adnexa that frequently recurs and metastasizes, and effective therapies beyond surgical excision are lacking. There remains a critical need to define the molecular-genetic drivers of the disease to understand carcinomagenesis and progression and to devise novel treatment strategies. We present next-generation sequencing of a targeted panel of cancer-associated genes in 42 and whole transcriptome RNA sequencing from eight OA sebaceous carcinomas from 29 patients. We delineate two potentially distinct molecular-genetic subtypes of OA sebaceous carcinoma. The first is defined by somatic mutations impacting TP53 and/or RB1 [20/29 (70%) patients, including 10 patients whose primary tumors contained coexisting TP53 and RB1 mutations] with frequent concomitant mutations affecting NOTCH genes. These tumors arise in older patients and show frequent local recurrence. The second subtype [9/29 (31%) patients] lacks mutations affecting TP53, RB1, or NOTCH family members, but in 44% (4/9) of these tumors, RNA sequencing and in situ hybridization studies confirm transcriptionally active high-risk human papillomavirus. These tumors arise in younger patients and have not shown local recurrence. Together, our findings establish a potential molecular-genetic framework by which to understand the development and progression of OA sebaceous carcinoma and provide key molecular-genetic insights to direct the design of novel therapeutic interventions.

Merkel cell polyomavirus-specific immune responses in patients with Merkel cell carcinoma receiving anti-PD-1 therapy

BackgroundMerkel cell carcinoma (MCC) is an aggressive skin cancer that frequently responds to anti-PD-1 therapy. MCC is associated with sun exposure and, in 80% of cases, Merkel cell polyomavirus (MCPyV). MCPyV-specific T and B cell responses provide a unique opportunity to study cancer-specific immunity throughout PD-1 blockade therapy.MethodsImmune responses were assessed in patients (n = 26) with advanced MCC receiving pembrolizumab. Peripheral blood mononuclear cells (PBMC) were collected at baseline and throughout treatment. MCPyV-oncoprotein antibodies were quantified and T cells were assessed for MCPyV-specificity via tetramer staining and/or cytokine secretion. Pre-treatment tumor biopsies were analyzed for T cell receptor clonality.ResultsMCPyV oncoprotein antibodies were detectable in 15 of 17 (88%) of virus-positive MCC (VP-MCC) patients. Antibodies decreased in 10 of 11 (91%) patients with responding tumors. Virus-specific T cells decreased over time in patients who had a complete response, and increased in patients who had persistent disease. Tumors that were MCPyV(+) had a strikingly more clonal (less diverse) intratumoral TCR repertoire than virus-negative tumors (p = 0.0001).ConclusionsCancer-specific T and B cell responses generally track with disease burden during PD-1 blockade, in proportion to presence of antigen. Intratumoral TCR clonality was significantly greater in VP-MCC than VN-MCC tumors, suggesting expansion of a limited number of dominant clones in response to fewer immunogenic MCPyV antigens. In contrast, VN-MCC tumors had lower clonality, suggesting a diverse T cell response to numerous neoantigens. These findings reveal differences in tumor-specific immunity for VP-MCC and VN-MCC, both of which often respond to anti-PD-1 therapy.

Detection of High-Risk Human Papillomavirus in Oral Cavity Squamous Cell Carcinoma Using Multiple Analytes and Their Role in Patient Survival.

PurposeAccurate detection of human papillomavirus (HPV) in oral cavity squamous cell carcinoma (OSCC) is essential to understanding the role of HPV in disease prognosis and management of patients. We used different analytes and methods to understand the true prevalence of HPV in a cohort of patients with OSCC with different molecular backgrounds, and we correlated HPV data with patient survival.MethodsWe integrated data from multiple analytes (HPV DNA, HPV RNA, and p16), assays (immunohistochemistry, polymerase chain reaction [PCR], quantitative PCR [qPCR], and digital PCR), and molecular changes (somatic mutations and DNA methylation) from 153 patients with OSCC to correlate p16 expression, HPV DNA, and HPV RNA with HPV incidence and patient survival.ResultsHigh prevalence (33% to 58%) of HPV16/18 DNA did not correlate with the presence of transcriptionally active viral genomes (15%) in tumors. Eighteen percent of the tumors were p16 positive and only 6% were both HPV DNA and HPV RNA positive. Most tumors with relatively high copy number HPV DNA and/or HPV RNA, but not with HPV DNA alone (irrespective of copy number), were wild-type for TP53 and CASP8 genes. In our study, p16 protein, HPV DNA, and HPV RNA, either alone or in combination, did not correlate with patient survival. Nine HPV-associated genes stratified the virus-positive from the virus-negative tumor group with high confidence (P < .008) when HPV DNA copy number and/or HPV RNA were considered to define HPV positivity, and not HPV DNA alone, irrespective of copy number (P < .2).ConclusionIn OSCC, the presence of both HPV RNA and p16 is rare. HPV DNA alone is not an accurate measure of HPV positivity and therefore may not be informative. HPV DNA, HPV RNA, and p16 do not correlate with patients’ outcome.

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.

National treatment times in oropharyngeal cancer treated with primary radiation or chemoradiation

ObjectiveTo characterize treatment delays in oropharyngeal cancer treated with radiation in a national sample, identify factors associated with delays, and associate treatment delays with survival. Materials and MethodsWe included adults in the National Cancer Database treated for oropharyngeal cancer with primary radiation or chemoradiation 2010–2013. We characterized diagnosis-to-treatment initiation, radiation treatment duration, and diagnosis-to-treatment end intervals as medians. We examined delays for association with patient, tumor, and treatment characteristics and with overall survival with multivariable logistic and Cox proportional hazards regression, respectively. Results4089 patients were included; 12% received radiation alone and 88% chemoradiation. The incidence of human papilloma virus-associated tumors was 64%. Median durations of diagnosis-to-treatment initiation, radiation duration, and diagnosis-to-treatment end were 35, 50, and 87 days, respectively. Human papilloma virus-positive tumors were linked to decreased delays in radiation treatment duration and diagnosis-to-treatment end (OR = 0.72 (0.60–0.85), p < 0.001 and OR = 0.79 (0.66–0.95), p = 0.010, respectively). Delays in radiation treatment duration and diagnosis-to-treatment end were negatively associated with overall survival (HR = 1.23 (1.03–1.47), p = 0.024 and 1.24 (1.04–1.48), p = 0.017, respectively). When examined separately, radiation duration remained associated with decreased overall survival in patients with human papilloma virus-negative (HR = 1.29 (1.03–1.63), p = 0.030) but not human papilloma virus-positive tumors (HR = 1.17 (0.89–1.54), p = 0.257). ConclusionThese median durations can serve as national benchmarks. Diagnosis-to-treatment end interval is associated with overall survival in all patients, and radiation treatment duration in patients with human papilloma virus-negative tumors. These intervals could be considered quality indicators for oropharyngeal squamous cell carcinoma treated with primary radiation or chemoradiation.

Merkel Cell Carcinoma in the Age of Immunotherapy: Facts and Hopes.

Merkel cell carcinoma (MCC) is a rare (∼2,000 U.S. cases/year) but aggressive neuroendocrine tumor of the skin. For advanced MCC, cytotoxic chemotherapy only infrequently (<10% of cases) offers durable clinical responses (>1 year), suggesting a great need for improved therapeutic options. In 2008, the Merkel cell polyomavirus (MCPyV) was discovered and is clonally integrated in approximately 80% of MCC tumors. The remaining 20% of MCC tumors have large numbers of UV-associated mutations. Importantly, both the UV-induced neoantigens in virus-negative tumors and the MCPyV T antigen oncogenes that are required for virus-positive tumor growth are immunogenic. Indeed, antigen-specific T cells detected in patients are frequently dysfunctional/"exhausted," and the inhibitory ligand, PD-L1, is often present in MCC tumors. These findings led to recent clinical trials involving PD-1 pathway blockade in advanced MCC. The combined data from these trials involving three PD-1 pathway blocking agents-avelumab, pembrolizumab, and nivolumab-indicated a high frequency of durable responses in treated patients. Of note, prior treatment with chemotherapy was associated with decreased response rates to PD-1 checkpoint blockade. Over the past year, these striking data led to major changes in advanced MCC therapy, including the first-ever FDA drug approval for this disease. Despite these successes, approximately 50% of patients with MCC do not persistently benefit from PD-1 pathway blockade, underscoring the need for novel strategies to broaden antitumor immune responses in these patients. Here, we highlight recent progress in MCC including the underlying mechanisms of immune evasion and emerging approaches to augment the efficacy of PD-1 pathway blockade. Clin Cancer Res; 24(9); 2035-43. ©2017 AACR.

Frameshift events predict anti-PD-1/L1 response in head and neck cancer.

Programmed cell death protein 1 (PD-1) inhibitors have efficacy in treating squamous cell carcinoma of the head and neck (SCCHN), but objective response rates are low. PD-1 ligand (PD-L1) expression alone is not considered a robust predictor of response and additional biomarkers are needed. This 3-year observational cohort followed 126 SCCHN patients treated with anti-PD-1/L1 therapy. Prior to treatment, 81 (64%) had targeted massively parallel tumor sequencing. Of these, 42 (52%) underwent fluorescence-activated cell sorting and PD-L1 immunohistochemistry for tumor immunoprofiling. Six (5%) complete responses (CRs) and 11 (9%) partial responses (PRs) were observed. Those treated with prior chemotherapy (98, 78%) versus only surgery and/or radiation had longer overall survival (OS) (10 vs. 3 months, P = 0.02). Smokers had a higher total mutational burden (TMB) (P = 0.01). Virus-positive patients had a lower TMB (P < 0.01) and improved OS (P = 0.02). Among virus-negative responders, NOTCH1 and SMARCA4 were more frequently mutated and frameshift events in tumor suppressor genes occurred more frequently (P = 0.03). Higher TMB and CD8+ T cell infiltrates predicted anti-PD-1/L1 benefit (P < 0.01, P < 0.01, respectively) among virus-negative tumors. TIM-3/LAG-3 coexpression with PD-1 was higher on T cells among nonresponders (P = 0.03 and 0.02, respectively). Somatic frameshift events in tumor suppressor genes and higher TMB among virus-negative SCCHN tumors predict anti-PD-1/L1 response.

Genetic profiles of different subsets of Merkel cell carcinoma show links between combined and pure MCPyV-negative tumors

Tumorigenesis in Merkel cell carcinoma (MCC) is driven by (1) clonal integration of the Merkel cell polyomavirus (MCPyV) in neoplastic cells and/or (2) genetic damage by ultraviolet (UV) light. A higher mutational burden, a UV-mutational signature, and many mutations in the TP53 and RB1 genes characterize the virus-negative subset. MCPyV-negative MCCs include combined (often squamous and neuroendocrine) and pure (neuroendocrine) tumors. Because a combined morphology could elude detection microscopically, we sought a genetic link between combined and pure virus-negative tumors. From a global cohort of 46 cases, 9 pure MCPyV-positive, 9 pure MCPyV-negative, and 10 combined MCPyV-negative MCCs were studied by genome-wide microarray in search of copy number aberrations. The entire cohort (n=46) was evaluated by next-generation sequencing for mutations in selected tumor suppressor genes and oncogenes. More copy number aberrations and a greater fraction of the genome were changed in combined and pure MCPyV-negative tumors relative to MCPyV-positive cases (P<.01 for all comparisons). No difference in these parameters was found between the 2 MCPyV-negative groups. Copy number loss of RB1 or an inactivating RB1 mutation (either or both) was common in combined (8/10, 80%) and pure (7/9, 78%) MCPyV-negative tumors but not MCPyV-positive cases (1/9, 11%). A similar trend was seen for TP53 (combined [2/10, 20%] and pure virus-negative tumors [5/9, 56%] showed gene copy number loss or mutations contrasted with pure virus-positive cases [0/9, 0%]). The shared genetic profiles of combined and pure MCPyV-negative tumors link these subsets and separate them from MCPyV-positive tumors.

579 High-risk human papillomavirus infection in Bowen’s disease and Squamous Cell Carcinomas of the hands

High-risk (HR) mucosal human papillomaviruses (HPV) are implicated as causative agent in the development of some cutaneous cancers, in particular squamous cell carcinomas (SCC) of the hands. Reported prevalence rates of HR HPV vary from 0-89%. We investigated archived tissues (28 Bowen’s disease (BD) and 9 SCC of the hands) for the presence of HR HPV DNA and the prevalent genotype by real-time PCR. Expression of p16, p53, and epidermal growth factor receptor (EGFR) was determined by immunohistochemistry and data analysed using the HistoQuest software. Viral DNA was detected in 61% of the tumors tested (BD: 54%, SCC: 33%) with HR HPV16 being the predominant type (73%), followed by 33, 52, and, in an HIV-infected patient, the rare type 26. The vast majority of the tumors was p16-positive and no significant difference was observed between virus-positive and -negative entities (82 vs. 100%, respectively). Few cases of BD (12%), which were negative for viral DNA, but not any of SCC stained positive for p53. EGFR-positivity was detected in 36% of BD and 11% of SCC and not linked to viral DNA status. Here we provide additional evidence for the etiological role of mucosal HR HPV in the development of cutaneous BD and SCC of the hands in immunocompetent patients. In contrast to HR HPV-induced cancers of the anogenital and oropharyngeal tract, p16 expression was not associated with HPV DNA positivity and, hence, does not represent a good surrogate marker for HR HPV infection in skin tumors. Limited expression of mutated p53 was observed in some virus-negative tumors, indicating a causative involvement of UV light adjunct to HR HPV infection. Given the rare EGFR expression in the SCC of the hands, EGFR inhibition does not seem to represent a suitable therapeutic option for this subset, however, more studies encompassing a higher number of tumors are warranted. Taken together, our findings suggest that BD and SCC of the hands represent a distinct entity within cutaneous cancers.

Abstract CT074: Non-comparative, open-label, multiple cohort, phase 1/2 study to evaluate nivolumab (NIVO) in patients with virus-associated tumors (CheckMate 358): Efficacy and safety in Merkel cell carcinoma (MCC)

Abstract Background: NIVO (anti-PD-1) is approved for the treatment of several cancers including advanced melanoma, but its efficacy in other types of skin cancer has not yet been evaluated. MCC is a rare and aggressive form of skin cancer, with most tumors being associated with the Merkel cell polyomavirus. MCCs frequently express PD-L1, and MCC-reactive T cells express PD-1. Methods: In CheckMate 358 (NCT02488759), patients (pts) with 5 types of advanced virus-associated cancers who had received ≤2 prior therapies, with an ECOG PS of 0-1, were eligible to receive NIVO 240 mg Q2W until progression or unacceptable toxicity. Key exclusion criteria were active brain metastases, autoimmune disease, hepatitis, and HIV infection. Primary endpoints included objective response rate (ORR by RECIST v1.1) and safety; secondary endpoints were duration of response, progression-free survival (PFS), and overall survival (OS). Twenty-five pts with MCC were treated with a median follow-up of 26 wks (range: 5-35). Results: Among 25 treated pts, median age was 66 yrs, 68% were male, and 60% were treatment-naive; 12 of 18 (67%) tested tumors were virus-positive. In 22 response-evaluable pts, ORR was 68% (table) with ongoing responses in 13 of 15 (87%) pts. Responses occurred in treatment-naive pts (71%), in pts with 1-2 prior systemic therapies (63%), and in both virus-positive and virus-negative tumors; 67% of responses occurred at ~8 weeks. At 3 months, PFS and OS rates were 82% and 92%, respectively. Treatment-related adverse events of any grade and grade 3/4 occurred in 68% and 20% of pts; 12% of pts had treatment-related AEs that led to NIVO discontinuation. Response to treatmentResponse-evaluable pts (N=22)Treatment-naive pts (n=14)Pts with 1-2 prior systemic therapies (n=8)Best overall response – n (%)Complete response3 (14)3 (21)0Partial response12 (55)7 (50)5 (63)Stable disease4 (18)3 (21)1 (13)Progressive disease3 (14)1 (7)2 (25)ORR – % (95% CI)68 (45–86)71 (42–92)63 (25–92)Time to response, months; median (range)2.0 (1.8–5.3)––Duration of response, months; median (range)Not reached (0.0–5.6)–– Conclusions: NIVO induces rapid and durable tumor regressions in the majority of treatment-naive and treatment-experienced pts with advanced MCC, with a manageable safety profile. Updated clinical response and biomarker data will be presented. Citation Format: Suzanne L. Topalian, Shailender Bhatia, Antoine Hollebecque, Ahmad Awada, Jan Paul De Boer, Ragini R. Kudchadkar, Anthony Goncalves, Jean-Pierre Delord, Uwe M. Martens, Jose Maria Lopez Picazo, Ana Oaknin, William C. Spanos, Raid Aljumaily, William H. Sharfman, Shangbang Rao, Ibrahima Soumaoro, Alexander Cao, Paul Nghiem, Dirk Schadendorf. Non-comparative, open-label, multiple cohort, phase 1/2 study to evaluate nivolumab (NIVO) in patients with virus-associated tumors (CheckMate 358): Efficacy and safety in Merkel cell carcinoma (MCC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr CT074. doi:10.1158/1538-7445.AM2017-CT074

Abstract CT096: Clinical activity, immune and viral correlates of PD-1 blockade with pembrolizumab as first systemic therapy in patients with advanced Merkel cell carcinoma

Abstract Background: Merkel cell carcinoma (MCC) is an aggressive skin cancer linked to UV exposure and the Merkel cell polyomavirus (MCPyV). Cytotoxic chemotherapy is associated with high response rates in patients (pts) with metastatic MCC, although responses are seldom durable and median progression-free survival is only 13 weeks. MCC may be responsive to PD-1 pathway blockade as tumors often express PD-L1 and MCPyV-specific T cells express the inhibitory co-receptor PD-1. Methods: In this open-label, phase II trial by the Cancer Immunotherapy Trials Network (NCT02267603), adults with advanced/metastatic MCC and no prior systemic therapy were enrolled. Pembrolizumab, a humanized IgG4 anti-PD-1 monoclonal antibody, was given IV every 3 weeks (2 mg/kg). Response was assessed by RECIST 1.1 every 9-12 weeks. Presence of MCPyV was assessed by measuring serum antibody titers to the MCPyV oncoprotein and/or quantifying tumor oncoprotein expression by immunohistochemistry (IHC). Results: Twenty-six pts were treated (median duration 22 weeks, range 4 to 49 weeks as of 1/8/16 dataset). Twenty-three pts had at least one documented radiologic or clinical assessment of response. Fifteen of 23 evaluable pts (65%) responded (4 complete responses and 11 partial responses); 2 additional pts had stable disease and 6 had progressive disease as best response. Fourteen of 15 responses (93%) were ongoing at last follow-up. Ten responders had at least one follow-up evaluation with response duration ranging from 8+ to 27+ weeks beyond initial documented response. Treatment was generally well tolerated with mostly grade 1 or 2 adverse events. Two pts developed severe drug-related toxicities including grade 4 myocarditis (n = 1) and grade 4 transaminase elevation (n = 1), both of which improved with corticosteroid treatment. Both pts have ongoing tumor responses despite discontinuation of pembrolizumab. Sixteen of 26 pts (62%) were classified as having virus-positive MCC. Among the 23 evaluable pts, 9 of 14 (64%) of those with virus positive tumors responded, while 6 of 9 (67%) of pts with virus negative tumors responded. Analyses of T cells specific to MCPyV and titers of oncoprotein antibodies during therapy, as well as IHC characterization of tumor biopsies including PD-L1 expression are ongoing. Conclusions: First-line therapy with pembrolizumab in pts with advanced MCC is associated with frequent (65%) and durable responses. Notably, the response rate was similar among pts with virus-positive and virus-negative tumors. While virus-positive tumors are known to express highly antigenic MCPyV oncoproteins, virus-negative tumors are typically UV-induced and display strikingly elevated mutational burdens generating putative neo-antigens. Thus, potentially through distinct mechanisms, both virus-positive and virus-negative MCC tumors appear to be immunogenic and frequently responsive to anti-PD-1 therapy. Citation Format: Paul Nghiem, Shailender Bhatia, Evan Lipson, Ragini Kudchadkar, Natalie Miller, Adil Daud, Steven Fling, Philip Friedlander, Harriet Kluger, Holbrook Kohrt, Lisa Lundgren, Kim Margolin, Thomas Olencki, Sunil Reddy, Erica Shantha, William Sharfman, Elad Sharon, Michi Shinohara, John Thompson, Jennifer Yearley, Suzanne Topalian, Martin Cheever. Clinical activity, immune and viral correlates of PD-1 blockade with pembrolizumab as first systemic therapy in patients with advanced Merkel cell carcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr CT096.

PD-1 Blockade with Pembrolizumab in Advanced Merkel-Cell Carcinoma

BackgroundMerkel-cell carcinoma is an aggressive skin cancer that is linked to exposure to ultraviolet light and the Merkel-cell polyomavirus (MCPyV). Advanced Merkel-cell carcinoma often responds to chemotherapy, but responses are transient. Blocking the programmed death 1 (PD-1) immune inhibitory pathway is of interest, because these tumors often express PD-L1, and MCPyV-specific T cells express PD-1.MethodsIn this multicenter, phase 2, noncontrolled study, we assigned adults with advanced Merkel-cell carcinoma who had received no previous systemic therapy to receive pembrolizumab (anti–PD-1) at a dose of 2 mg per kilogram of body weight every 3 weeks. The primary end point was the objective response rate according to Response Evaluation Criteria in Solid Tumors, version 1.1. Efficacy was correlated with tumor viral status, as assessed by serologic and immunohistochemical testing.ResultsA total of 26 patients received at least one dose of pembrolizumab. The objective response rate among the 25 patients with at least one evaluation during treatment was 56% (95% confidence interval [CI], 35 to 76); 4 patients had a complete response, and 10 had a partial response. With a median follow-up of 33 weeks (range, 7 to 53), relapses occurred in 2 of the 14 patients who had had a response (14%). The response duration ranged from at least 2.2 months to at least 9.7 months. The rate of progression-free survival at 6 months was 67% (95% CI, 49 to 86). A total of 17 of the 26 patients (65%) had virus-positive tumors. The response rate was 62% among patients with MCPyV-positive tumors (10 of 16 patients) and 44% among those with virus-negative tumors (4 of 9 patients). Drug-related grade 3 or 4 adverse events occurred in 15% of the patients.ConclusionsIn this study, first-line therapy with pembrolizumab in patients with advanced Merkel-cell carcinoma was associated with an objective response rate of 56%. Responses were observed in patients with virus-positive tumors and those with virus-negative tumors. (Funded by the National Cancer Institute and Merck; ClinicalTrials.gov number, NCT02267603.)

Merkel Cell Carcinoma Therapeutic Update.

Merkel cell carcinoma (MCC) is a rare and aggressive neuroendocrine tumor of the skin. Early-stage disease can be cured with surgical resection and radiotherapy (RT). Sentinel lymph node biopsy (SLNB) is an important staging tool, as a microscopic MCC is frequently identified. Adjuvant RT to the primary excision site and regional lymph node bed may improve locoregional control. However, newer studies confirm that patients with biopsy-negative sentinel lymph nodes may not benefit from regional RT. Advanced MCC currently lacks a highly effective treatment as responses to chemotherapy are not durable. Recent work suggests that immunotherapy targeting the programmed cell death receptor 1/programmed cell death ligand 1 (PD-1/PD-L1) checkpoint holds great promise in treating advanced MCC and may provide durable responses in a portion of patients. At the same time, high-throughput sequencing studies have demonstrated significant differences in the mutational profiles of tumors with and without the Merkel cell polyomavirus (MCV). An important secondary endpoint in the ongoing immunotherapy trials for MCC will be determining if there is a response difference between the virus-positive MCC tumors that typically lack a large mutational burden and the virus-negative tumors that have a large number of somatic mutations and predicted tumor neoantigens. Interestingly, sequencing studies have failed to identify a highly recurrent activated driver pathway in the majority of MCC tumors. This may explain why targeted therapies can demonstrate exceptional responses in case reports but fail when treating all comers with MCC. Ultimately, a precision medicine approach may be more appropriate for treating MCC, where identified driver mutations are used to direct targeted therapies. At a minimum, stratifying patients in future clinical trials based on tumor viral status should be considered as virus-negative tumors are more likely to harbor activating driver mutations.

Hotspot mutations in polyomavirus positive and negative Merkel cell carcinomas

Merkel cell polyomavirus (MCV) infection underlies most Merkel cell carcinoma (MCC), a primary neuroendocrine carcinoma of the skin. While previous research has focused on MCV-positive MCC tumors, less is known about the oncogenesis in MCV-negative tumors. In this study, we analyzed mutational status of 27 MCC tumors with known MCV status for hotspot regions of 50 cancer-related genes by targeted next-generation sequencing using the Ion AmpliSeq Cancer Hotspot Panel. In addition to previously reported TP53, KIT, and PIK3CA gene mutations, we found somatic mutations in the tyrosine kinase domain of the EGFR gene in a small proportion of the cells in six tumor tissues. RB1 mutations were seen only in virus negative tumors. Hotspot mutations were more frequent in MCV-negative tumors, although the difference was not statistically significant. No clear hotspot mutation profile was observed. Novel RB1 mutations were detected only in MCV-negative tumors.