Nicole R. LeBoeuf

Skin Effector Memory T Cells Do Not Recirculate and Provide Immune Protection in Alemtuzumab-Treated CTCL Patients

Alemtuzumab depletes malignant T cells but spares skin resident effector memory T cells, treating L-CTCL without increased risk of infection. Resolving Cutaneous T Cell Lymphoma Becoming more active figures prominently in many New Year’s resolutions. We vow to get off the couch, or up from the lab bench, and get in shape. Yet, after a 2- to 3-week frenzy, spaces appear in gym parking lots as most people resume their sedentary life-styles. Some but not all memory T cells mimic this cyclic action. Clark et al. now exploit this difference to successfully treat cutaneous T cell lymphoma (CTCL) without increasing patients’ risk of infection. CTCL is a cancer of skin-homing T cells that can either be restricted to the skin—mycosis fungoides (MF)—or extend to the blood—leukemic CTCL (L-CTCL). MF and L-CTCL are caused by malignancies in two different types of memory T cells: skin resident effector memory T cells (TEM) and central memory T cells (TCM), respectively. Clark et al. found that treating patients with a low dose of alemtuzumab—a monoclonal antibody to CD52, a protein found on the surface of some mature lymphocytes—has a therapeutic effect on L-CTCL but not MF. Indeed, alemtuzumab depleted all T cells, both benign and malignant, from the blood; however, in the skin, only TCM were depleted with alemtuzumab treatment. This effect depended on the presence of neutrophils—phagocytic cells found in the blood but rare in normal skin—which suggests that TCM but not TEM recirculate in the blood. Importantly, the remaining skin resident TEM in the L-CTCL patients may have a protective function, because risk of infection was not heightened in the treated patients. Thus, alemtuzumab destroys the more active malignant cells while sparing the more sessile population, resulting in cancer therapy with retained immunity and, hopefully, the chance for these patients to break many more New Year’s resolutions. Cutaneous T cell lymphoma (CTCL) is a cancer of skin-homing T cells with variants that include leukemic CTCL (L-CTCL), a malignancy of central memory T cells (TCM), and mycosis fungoides (MF), a malignancy of skin resident effector memory T cells (TEM). We report that low-dose alemtuzumab (αCD52) effectively treated patients with refractory L-CTCL but not MF. Alemtuzumab depleted all T cells in blood and depleted both benign and malignant TCM from skin, but a diverse population of skin resident TEM remained in skin after therapy. T cell depletion with alemtuzumab required the presence of neutrophils, a cell type frequent in blood but rare in normal skin. These data suggest that TCM were depleted because they recirculate between the blood and the skin, whereas skin resident TEM were spared because they are sessile and non-recirculating. After alemtuzumab treatment, skin T cells produced lower amounts of interleukin-4 and higher amounts of interferon-γ. Moreover, there was a marked lack of infections in alemtuzumab-treated L-CTCL patients despite the complete absence of T cells in the blood, suggesting that skin resident TEM can protect the skin from pathogens even in the absence of T cell recruitment from the circulation. Together, these data suggest that alemtuzumab may treat refractory L-CTCL without severely compromising the immune response to infection by depleting circulating TCM but sparing the skin resident TEM that provide local immune protection of the skin.

Ipilimumab for Patients with Relapse after Allogeneic Transplantation

BACKGROUND Loss of donor-mediated immune antitumor activity after allogeneic hematopoietic stem-cell transplantation (HSCT) permits relapse of hematologic cancers. We hypothesized that immune checkpoint blockade established by targeting cytotoxic T-lymphocyte-associated protein 4 with ipilimumab could restore antitumor reactivity through a graft-versus-tumor effect. METHODS We conducted a phase 1/1b multicenter, investigator-initiated study to determine the safety and efficacy of ipilimumab in patients with relapsed hematologic cancer after allogeneic HSCT. Patients received induction therapy with ipilimumab at a dose of 3 or 10 mg per kilogram of body weight every 3 weeks for a total of 4 doses, with additional doses every 12 weeks for up to 60 weeks in patients who had a clinical benefit. RESULTS A total of 28 patients were enrolled. Immune-related adverse events, including one death, were observed in 6 patients (21%), and graft-versus-host disease (GVHD) that precluded further administration of ipilimumab was observed in 4 patients (14%). No responses that met formal response criteria occurred in patients who received a dose of 3 mg per kilogram. Among 22 patients who received a dose of 10 mg per kilogram, 5 (23%) had a complete response, 2 (9%) had a partial response, and 6 (27%) had decreased tumor burden. Complete responses occurred in 4 patients with extramedullary acute myeloid leukemia and 1 patient with the myelodysplastic syndrome developing into acute myeloid leukemia. Four patients had a durable response for more than 1 year. Responses were associated with in situ infiltration of cytotoxic CD8+ T cells, decreased activation of regulatory T cells, and expansion of subpopulations of effector T cells in the blood. CONCLUSIONS Our early-phase data showed that administration of ipilimumab was feasible in patients with recurrent hematologic cancers after allogeneic HSCT, although immune-mediated toxic effects and GVHD occurred. Durable responses were observed in association with several histologic subtypes of these cancers, including extramedullary acute myeloid leukemia. (Funded by the National Institutes of Health and others; ClinicalTrials.gov number, NCT01822509.).

The Public Repository of Xenografts Enables Discovery and Randomized Phase II-like Trials in Mice

More than 90% of drugs with preclinical activity fail in human trials, largely due to insufficient efficacy. We hypothesized that adequately powered trials of patient-derived xenografts (PDX) in mice could efficiently define therapeutic activity across heterogeneous tumors. To address this hypothesis, we established a large, publicly available repository of well-characterized leukemia and lymphoma PDXs that undergo orthotopic engraftment, called the Public Repository of Xenografts (PRoXe). PRoXe includes all de-identified information relevant to the primary specimens and the PDXs derived from them. Using this repository, we demonstrate that large studies of acute leukemia PDXs that mimic human randomized clinical trials can characterize drug efficacy and generate transcriptional, functional, and proteomic biomarkers in both treatment-naive and relapsed/refractory disease.

TCR sequencing facilitates diagnosis and identifies mature T cells as the cell of origin in CTCL

High-throughput TCR sequencing can accurately diagnose and discriminate CTCL cells in skin. Discriminating taste for CTCL Cutaneous T cell lymphoma (CTCL) is a potentially debilitating disease, but early stages resemble rashes of less dangerous inflammatory skin diseases. Now, Kirsch et al. report that high-throughput TCR sequencing (HTS) can be used to distinguish CTCL from benign inflammatory disease by identifying T cell clones. This diagnostic was more sensitive and specific than the current standard of care and was also able to determine therapeutic response and identify early recurrence. The authors then used HTS to gain insight into CTCL pathogenesis, reporting that the malignancy derived from mature T cells that may have a specialized niche in the skin. Early diagnosis of cutaneous T cell lymphoma (CTCL) is difficult and takes on average 6 years after presentation, in part because the clinical appearance and histopathology of CTCL can resemble that of benign inflammatory skin diseases. Detection of a malignant T cell clone is critical in making the diagnosis of CTCL, but the T cell receptor γ (TCRγ) polymerase chain reaction (PCR) analysis in current clinical use detects clones in only a subset of patients. High-throughput TCR sequencing (HTS) detected T cell clones in 46 of 46 CTCL patients, was more sensitive and specific than TCRγ PCR, and successfully discriminated CTCL from benign inflammatory diseases. HTS also accurately assessed responses to therapy and facilitated diagnosis of disease recurrence. In patients with new skin lesions and no involvement of blood by flow cytometry, HTS demonstrated hematogenous spread of small numbers of malignant T cells. Analysis of CTCL TCRγ genes demonstrated that CTCL is a malignancy derived from mature T cells. There was a maximal T cell density in skin in benign inflammatory diseases that was exceeded in CTCL, suggesting that a niche of finite size may exist for benign T cells in skin. Last, immunostaining demonstrated that the malignant T cell clones in mycosis fungoides and leukemic CTCL localized to different anatomic compartments in the skin. In summary, HTS accurately diagnosed CTCL in all stages, discriminated CTCL from benign inflammatory skin diseases, and provided insights into the cell of origin and location of malignant CTCL cells in skin.

Managing toxicities associated with immune checkpoint inhibitors: consensus recommendations from the Society for Immunotherapy of Cancer (SITC) Toxicity Management Working Group

Cancer immunotherapy has transformed the treatment of cancer. However, increasing use of immune-based therapies, including the widely used class of agents known as immune checkpoint inhibitors, has exposed a discrete group of immune-related adverse events (irAEs). Many of these are driven by the same immunologic mechanisms responsible for the drugs’ therapeutic effects, namely blockade of inhibitory mechanisms that suppress the immune system and protect body tissues from an unconstrained acute or chronic immune response. Skin, gut, endocrine, lung and musculoskeletal irAEs are relatively common, whereas cardiovascular, hematologic, renal, neurologic and ophthalmologic irAEs occur much less frequently. The majority of irAEs are mild to moderate in severity; however, serious and occasionally life-threatening irAEs are reported in the literature, and treatment-related deaths occur in up to 2% of patients, varying by ICI. Immunotherapy-related irAEs typically have a delayed onset and prolonged duration compared to adverse events from chemotherapy, and effective management depends on early recognition and prompt intervention with immune suppression and/or immunomodulatory strategies. There is an urgent need for multidisciplinary guidance reflecting broad-based perspectives on how to recognize, report and manage organ-specific toxicities until evidence-based data are available to inform clinical decision-making. The Society for Immunotherapy of Cancer (SITC) established a multidisciplinary Toxicity Management Working Group, which met for a full-day workshop to develop recommendations to standardize management of irAEs. Here we present their consensus recommendations on managing toxicities associated with immune checkpoint inhibitor therapy.

Successful Treatment of a Progressive BRAF V600E–Mutated Anaplastic Pleomorphic Xanthoastrocytoma With Vemurafenib Monotherapy

Introduction Pleomorphic xanthoastrocytoma (PXA) is a rare brain tumor that most commonly affects children and young adults. PXA undergoes anaplastic transformation in 15% to 20% of patients. Although the prognosis is relatively favorable for patients with a WHO grade 2 PXA, data suggest that the prognosis for anaplastic PXA is significantly worse. Maximal resection is generally recommended, but the role of radiation or chemotherapy in the management of these tumors remains unclear. Alterations in the BRAF gene have been described in several pediatric low-grade gliomas. Approximately 70% of pilocytic astrocytomas contain BRAF fusions, resulting from a tandem duplication and rearrangement on 7q34 between BRAF and a gene centromeric to BRAF. This is in contrast with PXA, in which the described BRAF alteration is instead a BRAF mutation that results from an amino acid substitution replacing valine (V) with glutamic acid (E) at position 600. This BRAF V600E mutation is found in approximately 60% to 65% of WHO grade 2 and 3 PXAs, and is the same mutation that is found in approximately 50% of melanomas. Vemurafenib is a BRAF inhibitor that is approved for the treatment of BRAF-mutated metastatic melanoma in the United States and the European Union. There are several case reports of CNS melanoma metastases that were responsive to vemurafenib, and preliminary results from an open-label pilot study of vemurafenib for patients with melanoma and brain metastases suggest some activity. This evidence indicates that vemurafenib may penetrate CNS tumors. In addition, BRAF inhibition represses the growth of intracranial BRAF V600E pediatric malignant astrocytoma xenografts in mouse models. Hence, vemurafenib may have a role in the treatment of intracranial neoplasms with BRAF mutations. In support of this, we now present a case of a progressive BRAF V600E–mutated anaplastic PXA that was successfully treated with vemurafenib monotherapy.

Photodynamic therapy for multiple eruptive keratoacanthomas associated with vemurafenib treatment for metastatic melanoma.

BACKGROUND The development of keratoacanthomas (KAs) and well-differentiated squamous cell carcinomas (SCCs) is a known adverse effect of novel BRAF inhibitors such as vemurafenib. With multiple such neoplasms often arising after BRAF inhibitor therapy, surgical excision is often impractical. OBSERVATIONS We describe a patient with stage IV melanoma who received the BRAF inhibitor vemurafenib (recently approved by the US Food and Drug Administration) as part of a clinical trial and developed numerous diffuse, pathology-proven KAs and SCCs. The high number of lesions across a broad area precluded surgical treatment; instead, a noninvasive field approach using photodynamic therapy (PDT) was initiated. Compared with untreated tumors, most lesions demonstrated significant clinical regression following successive cycles of PDT. CONCLUSIONS Given vemurafenibs recent approval by the US Food and Drug Administration, we provide a timely case report on the effective use of PDT in the treatment of BRAF inhibitor-associated KAs and SCCs. Although further studies are needed to better understand the biological processes of these secondary neoplasms, our observation provides an alternative noninvasive solution for improving the quality of life for patients receiving BRAF inhibitor therapy.

Blastic Plasmacytoid Dendritic Cell Neoplasm Is Dependent on BCL2 and Sensitive to Venetoclax

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an aggressive hematologic malignancy with dismal outcomes for which no standard therapy exists. We found that primary BPDCN cells were dependent on the antiapoptotic protein BCL2 and were uniformly sensitive to the BCL2 inhibitor venetoclax, as measured by direct cytotoxicity, apoptosis assays, and dynamic BH3 profiling. Animals bearing BPDCN patient-derived xenografts had disease responses and improved survival after venetoclax treatment in vivo Finally, we report on 2 patients with relapsed/refractory BPDCN who received venetoclax off-label and experienced significant disease responses. We propose that venetoclax or other BCL2 inhibitors undergo expedited clinical evaluation in BPDCN, alone or in combination with other therapies. In addition, these data illustrate an example of precision medicine to predict treatment response using ex vivo functional assessment of primary tumor tissue, without requiring a genetic biomarker. SIGNIFICANCE Therapy for BPDCN is inadequate, and survival in patients with the disease is poor. We used primary tumor cell functional profiling to predict BCL2 antagonist sensitivity as a common feature of BPDCN, and demonstrated in vivo clinical activity of venetoclax in patient-derived xenografts and in 2 patients with relapsed chemotherapy-refractory disease. Cancer Discov; 7(2); 156-64. ©2016 AACR.This article is highlighted in the In This Issue feature, p. 115.

Update on the Management of High-Risk Squamous Cell Carcinoma

Cutaneous squamous cell carcinoma (CSCC) is the second most common malignancy occurring in white patients in the United States and incidence rates are increasing. While the majority of the 87,000-760,000 cases that occur yearly in the U.S. are curable, 4% develop lymph node metastases and 1.5% die from the disease. Given the frequency of occurrence of CSCC, it is estimated to cause as many deaths yearly as melanoma, with the majority occurring in patients with high risk tumors or in those at high risk for metastasis due to a variety of host factors, most commonly systemic immunosuppression. There are currently no standardized prognostic or treatment models to assist clinicians in most effectively identifying and managing these patients. Identification of patients at risk for poor outcomes as well as standardization regarding classification, staging, and treatment of high-risk tumors is critical for optimizing patient care. In this article, available literature on the classification and management of high risk CSCC is briefly summarized, emphasizing new information.

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.