Manisha Thakuria

Tumor-Specific T Cells in Human Merkel Cell Carcinomas: A Possible Role for Tregs and T-Cell Exhaustion in Reducing T-Cell Responses

Merkel cell carcinomas (MCC) are rare but highly malignant skin cancers associated with a novel polyomavirus. MCC tumors were infiltrated by T cells, including effector, central memory and regulatory T cells. Infiltrating T cells showed markedly reduced activation as evidenced by reduced expression of CD69 and CD25. Treatment of MCC tumors in vitro with IL-2 and IL-15 led to T cell activation, proliferation, enhanced cytokine production and loss of viable tumor cells from cultures. Expanded tumor-infiltrating lymphocytes showed TCR repertoire skewing and upregulation of CD137. MCC tumors implanted into immunodeficient mice failed to grow unless human T cells in the tumor grafts were depleted with denileukin diftitox, suggesting tumor-specific T cells capable of controlling tumor growth were present in MCC. Both CD4+ and CD8+ FOXP3+ regulatory T cells were frequent in MCC. 50% of non-activated T cells in MCC expressed PD-1, a marker of T-cell exhaustion, and PD-L1 and PD-L2 were expressed by a subset of tumor dendritic cells and macrophages. In summary, we observed tumor-specific T cells with suppressed activity in MCC tumors. Agents that stimulate T cell activity, block Treg function or inhibit PD-1 signaling may be effective in the treatment of this highly malignant skin cancer.

Merkel Cell Polyomavirus Exhibits Dominant Control of the Tumor Genome and Transcriptome in Virus-Associated Merkel Cell Carcinoma

ABSTRACT Merkel cell polyomavirus is the primary etiological agent of the aggressive skin cancer Merkel cell carcinoma (MCC). Recent studies have revealed that UV radiation is the primary mechanism for somatic mutagenesis in nonviral forms of MCC. Here, we analyze the whole transcriptomes and genomes of primary MCC tumors. Our study reveals that virus-associated tumors have minimally altered genomes compared to non-virus-associated tumors, which are dominated by UV-mediated mutations. Although virus-associated tumors contain relatively small mutation burdens, they exhibit a distinct mutation signature with observable transcriptionally biased kataegic events. In addition, viral integration sites overlap focal genome amplifications in virus-associated tumors, suggesting a potential mechanism for these events. Collectively, our studies indicate that Merkel cell polyomavirus is capable of hijacking cellular processes and driving tumorigenesis to the same severity as tens of thousands of somatic genome alterations. IMPORTANCE A variety of mutagenic processes that shape the evolution of tumors are critical determinants of disease outcome. Here, we sequenced the entire genome of virus-positive and virus-negative primary Merkel cell carcinomas (MCCs), revealing distinct mutation spectra and corresponding expression profiles. Our studies highlight the strong effect that Merkel cell polyomavirus has on the divergent development of viral MCC compared to the somatic alterations that typically drive nonviral tumorigenesis. A more comprehensive understanding of the distinct mutagenic processes operative in viral and nonviral MCCs has implications for the effective treatment of these tumors. A variety of mutagenic processes that shape the evolution of tumors are critical determinants of disease outcome. Here, we sequenced the entire genome of virus-positive and virus-negative primary Merkel cell carcinomas (MCCs), revealing distinct mutation spectra and corresponding expression profiles. Our studies highlight the strong effect that Merkel cell polyomavirus has on the divergent development of viral MCC compared to the somatic alterations that typically drive nonviral tumorigenesis. A more comprehensive understanding of the distinct mutagenic processes operative in viral and nonviral MCCs has implications for the effective treatment of these tumors.

Ex Vivo Profiling of PD-1 Blockade Using Organotypic Tumor Spheroids

Ex vivo systems that incorporate features of the tumor microenvironment and model the dynamic response to immune checkpoint blockade (ICB) may facilitate efforts in precision immuno-oncology and the development of effective combination therapies. Here, we demonstrate the ability to interrogate ex vivo response to ICB using murine- and patient-derived organotypic tumor spheroids (MDOTS/PDOTS). MDOTS/PDOTS isolated from mouse and human tumors retain autologous lymphoid and myeloid cell populations and respond to ICB in short-term three-dimensional microfluidic culture. Response and resistance to ICB was recapitulated using MDOTS derived from established immunocompetent mouse tumor models. MDOTS profiling demonstrated that TBK1/IKKε inhibition enhanced response to PD-1 blockade, which effectively predicted tumor response in vivo Systematic profiling of secreted cytokines in PDOTS captured key features associated with response and resistance to PD-1 blockade. Thus, MDOTS/PDOTS profiling represents a novel platform to evaluate ICB using established murine models as well as clinically relevant patient specimens.Significance: Resistance to PD-1 blockade remains a challenge for many patients, and biomarkers to guide treatment are lacking. Here, we demonstrate feasibility of ex vivo profiling of PD-1 blockade to interrogate the tumor immune microenvironment, develop therapeutic combinations, and facilitate precision immuno-oncology efforts. Cancer Discov; 8(2); 196-215. ©2017 AACR.See related commentary by Balko and Sosman, p. 143See related article by Deng et al., p. 216This article is highlighted in the In This Issue feature, p. 127.

Merkel Cell Carcinoma Presenting as Subcutaneous Breast Masses: An Uncommon Presentation of a Rare Neuroendocrine Neoplasm.

*Department of Dermatology, Brigham and Women’s Hospital and Dana Farber Cancer Institute, Boston, Massachusetts; Department of Medicine, Brigham and Women’s Hospital, Boston, Massachusetts; Department of Pathology, Brigham and Women’s Hospital, Boston, Massachusetts; Department of Radiation Oncology, Brigham and Women’s Hospital and Dana Farber Cancer Institute, Boston, Massachusetts; Department of Surgical Oncology, Brigham and Women’s Hospital and Dana Farber Cancer Institute, Boston, Massachusetts; **Department of Medical Oncology, Dana Farber Cancer Institute, Boston, Massachusetts

Papulopustular Acneiform Eruptions Resulting From Trastuzumab, a HER2 Inhibitor

The epidermal growth factor receptor (EGFR) family, human epidermal growth factor receptor (HER)1/ EGFR, HER2, HER3, and HER4, has been the target of an increasing number of oncologic therapies. It is wellknown that medications targeting HER1/EGFR commonly cause a papulopustular acneiform eruption. Despite the increasing use of HER2 inhibitors, including trastuzumab, in breast cancer management, reports of papulopustular eruptions in patients treated with HER2 inhibitors have been rare. Four women undergoing HER2-directed breast cancer therapy with trastuzumab developed papulopustular eruptions 7 to 22 days after therapy initiation. In 1 case, the eruption prompted treatment interruption. All patients’ eruptions resolved with skin-directed treatment and did not recur. At the last follow-up visit, all were alive with no evidence of breast carcinoma. These cases show that HER2 inhibitors might cause papulopustular reactions, similar to those classically reported with HER1/EGFR inhibition, possibly through HER2 homodimer and/or HER1-HER2 heterodimer inhibition. With the increasing use of targeted inhibition of the EGFR family, especially HER2, in patients with breast cancer, increased awareness of these reactions is imperative. Prompt recognition and appropriate treatment of patients receiving HER2 inhibitors, such as trastuzumab, could avoid treatment interruption, dose reduction, and impairment of patient quality of life.

Cytokeratin 17 is highly sensitive in discriminating cutaneous lymphadenoma (a distinct trichoblastoma variant) from basal cell carcinoma.

Cutaneous lymphadenoma (CL) is rare neoplasm that clinically and histologically resembles basal cell carcinoma (BCC). CL, composed of dermal basaloid epithelial islands with prominent admixed lymphocytes, characteristically contains cytokeratin 20 (CK20)‐positive Merkel cells (MCs). However, CK20 may be of limited use because of low MC density in small samples. CK17 is expressed diffusely throughout BCC. We investigated the discriminatory utility of CK17 and CK20 in CL and BCC.

Update on the Biology and Clinical Management of Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is a rare but aggressive neuroendocrine cutaneous malignancy, with a predilection for sun-exposed sites in elderly patients. Despite an incidence 30 times less than that of melanoma, its disease-specific mortality is three times higher. Management of MCC remains challenging because of a limited understanding of its molecular biology, lack of prospective clinical trials, and limitations associated with retrospective reviews of therapeutic options. With the recent discovery of an associated human polyomavirus, significant progress has been made in the understanding of the pathogenesis of this malignancy. With this progress, there has been increasing optimism regarding new tools in the therapeutic armamentarium to fight this deadly disease. Here we present an overview on MCC with an emphasis on the most recent biologic discoveries and the rationale for novel targeted and immunotherapies.