Paul R. Massey

The PDL1-PD1 axis converts human TH1 cells into regulatory T cells.

The inhibitory ligand PDL1 transforms immune cells from attackers into regulators. PDL1: Restoring the Peace With great power comes great responsibility. In superhero lore, special powers don’t separate the saviors from the evil villains they fight; instead, what matters is how the person behind the mask uses those powers. Immune cells are the superheroes of the body—they fight off infection and patrol the body for cancer. However, sometimes, even protective cells “go bad,” causing autoimmunity or graft-versus-host disease after transplant. Amarnath et al. now show that an inhibitory protein called programmed death ligand 1 (PDL1) can regulate renegade immune cells by converting immune response–promoting T helper type 1 (TH1) cells to regulatory T (Treg) cells—agents that selectively suppress activation of the immune system. TH1 cells secrete proinflammatory cytokines and are critical for the immune response to infection and cancer cells. In contrast to other subsets of TH cells, researchers believed TH1 cells to be relatively stable. However, PDL1 caused human TH1 cells to convert to Treg cells both in vitro and in vivo. These TH1-derived Treg cells inhibited graft-versus-host disease in mice after transplant. Moreover, inhibiting Treg differentiation by blocking the PDL1 receptor PD1 or pharmacologically inhibiting SHP1 and SHP2, which are signaling molecules that act downstream of PD1 activation, restored graft-versus-host disease in mice. These data provide the basis for future therapies: Because PDL1 is highly expressed on many cancers, inhibiting this pathway may restore T cell–mediated cancer surveillance; alternately, accentuating signaling through this pathway may prevent autoimmunity or graft-versus-host disease. With this knowledge, scientists and doctors may be able to ensure that T cells are the superheroes they are meant to be. Immune surveillance by T helper type 1 (TH1) cells is not only critical for the host response to tumors and infection, but also contributes to autoimmunity and graft-versus-host disease (GVHD) after transplantation. The inhibitory molecule programmed death ligand 1 (PDL1) has been shown to anergize human TH1 cells, but other mechanisms of PDL1-mediated TH1 inhibition such as the conversion of TH1 cells to a regulatory phenotype have not been well characterized. We hypothesized that PDL1 may cause TH1 cells to manifest differentiation plasticity. Conventional T cells or irradiated K562 myeloid tumor cells overexpressing PDL1 converted TBET+ TH1 cells into FOXP3+ regulatory T (Treg) cells in vivo, thereby preventing human-into-mouse xenogeneic GVHD (xGVHD). Either blocking PD1 expression on TH1 cells by small interfering RNA targeting or abrogation of PD1 signaling by SHP1/2 pharmacologic inhibition stabilized TH1 cell differentiation during PDL1 challenge and restored the capacity of TH1 cells to mediate lethal xGVHD. PD1 signaling therefore induces human TH1 cells to manifest in vivo plasticity, resulting in a Treg phenotype that severely impairs cell-mediated immunity. Converting human TH1 cells to a regulatory phenotype with PD1 signaling provides a potential way to block GVHD after transplantation. Moreover, because this conversion can be prevented by blocking PD1 expression or pharmacologically inhibiting SHP1/2, this pathway provides a new therapeutic direction for enhancing T cell immunity to cancer and infection.

Oral Anticancer Drugs: How Limited Dosing Options and Dose Reductions May Affect Outcomes in Comparative Trials and Efficacy in Patients

Historically, cancer medicine has avoided the problem of unequal dosing by comparing maximum-tolerated doses of intravenous regimens with proportionate dose reductions for toxicity. However, in recent years, with the development of numerous oral anticancer agents, dosing options are arbitrarily and increasingly limited by the size of pills. We contend that an underappreciated consequence of pill size is unequal dosing in comparative clinical trials and that this can have an impact on outcomes. We discuss how comparative effectiveness trials can be unbalanced and how the use of doses that are not sustainable might affect outcomes, especially marginal ones. We further argue that because of their poor tolerability and their limited dosing options, which often result in large dose adjustments in response to toxicity, the real-world clinical effectiveness of oral anticancer agents may be diminished and may not emulate results achieved in registration trials.

Hyperbaric oxygen therapy in necrotizing soft tissue infections

BACKGROUND Surgical debridement and antibiotics are the mainstays of therapy for patients with necrotizing soft tissue infections (NSTIs), but hyperbaric oxygen therapy (HBO) is often used as an adjunctive measure. Despite this, the efficacy of HBO remains unclear. We hypothesized that HBO would have no effect on mortality or amputation rates. METHODS We performed a retrospective analysis of our institutional experience from 2005 to 2009. Inclusion criteria were age > 18 y and discharge diagnosis of NSTI. We abstracted baseline demographics, physiology, laboratory values, and operative course from the medical record. The primary endpoint was in-hospital mortality; the secondary endpoint was extremity amputation rate. We compared baseline variables using Mann-Whitney, chi-square, and Fishers exact test, as appropriate. Significance was set at P < 0.05. RESULTS We identified 80 cases over the study period. The cohort was 54% male (n = 43) and 53% white (n = 43), and had a mean age of 55 ± 16 y. There were no significant differences in demographics, physiology, or comorbidities between groups. In-hospital mortality was not different between groups (16% in the HBO group versus 19% in the non-HBO group; P = 0.77). In patients with extremity NSTI, the amputation rate did not differ significantly between patients who did not receive HBO and those who did (17% versus 25%; P = 0.46). CONCLUSIONS Hyperbaric oxygen therapy does not appear to decrease in-hospital mortality or amputation rate after in patients with NSTI. There may be a role for HBO in treatment of NSTI; nevertheless, consideration of HBO should never delay operative therapy. Further evidence of efficacy is necessary before HBO can be considered the standard of care in NSTI.

Pentostatin plus cyclophosphamide safely and effectively prevents immunotoxin immunogenicity in murine hosts.

Purpose: The success of immunotoxin therapy of cancer is limited by host production of neutralizing antibodies, which are directed toward the Pseudomonas exotoxin A (PE) component. In this proof-of-principle study using a well-established murine model, we hypothesized that a newly developed immune depletion regimen consisting of pentostatin plus cyclophosphamide would abrogate anti-immunotoxin reactivity. Experimental Design: BALB/c hosts were injected weekly with recombinant immunotoxin (RIT) SS1P, which is an antimesothelin Fv antibody fragment genetically fused to a 38 kDa portion of PE, and has been evaluated in clinical trials. Experimental cohorts received induction chemotherapy consisting of pentostatin (P) plus cyclophosphamide (C) prior to initial RIT exposure; some cohorts received further maintenance PC therapy of varying intensity just prior to each weekly RIT challenge. Cohorts were monitored for T, B, myeloid cell depletion, and for total anti-SS1P antibody (Ab) formation. Results: Controls uniformly developed anti-SS1P Ab after the third RIT exposure. Induction PC therapy reduced the frequency of hosts with anti-SS1P Ab. Abrogation of antibody generation was improved by maintenance PC therapy: nearly 100% of recipients of intensive PC maintenance were free of anti-SS1P Ab after 9 weekly RIT doses. The most effective PC regimen yielded the greatest degree of host B-cell depletion, moderate T-cell depletion, and minimal myeloid cell depletion. Conclusions: Induction and maintenance PC chemotherapy safely prevented anti-immunotoxin antibody formation with uniform efficacy. These data suggest that immunotoxin therapy might be used in combination with pentostatin plus cyclophosphamide chemotherapy to improve the targeted therapy of cancer. Clin Cancer Res; 17(11); 3697–705. ©2011 AACR.

The Pentostatin Plus Cyclophosphamide Nonmyeloablative Regimen Induces Durable Host T Cell Functional Deficits and Prevents Murine Marrow Allograft Rejection

We describe a novel animal model of nonmyeloablative bone marrow transplantation (BMT) using the purine analog pentostatin. Other cohorts of mice received another purine analog, fludarabine, which we and others have previously evaluated in nonmyeloablative murine models. We evaluated pentostatin for its ability to (1) operate synergistically with cyclophosphamide to induce host T cell depletion; (2) induce host T cell suppression, as defined by modulation of cytokine secretion in vitro and abrogation of host-versus-graft reactivity in vivo; (3) constrain host T cell recovery post-therapy; and (4) prevent the rejection of T cell-depleted, fully major histocompatibility complex-mismatched bone marrow allografts. Relative to single-agent regimens, combination regimens with pentostatin and cyclophosphamide (PC) and with fludarabine and cyclophosphamide (FC) worked synergistically to deplete host CD4(+) and CD8(+) T cells. PC and FC regimens were developed that yielded similar levels of host T cell and myeloid cell depletion. In the setting of these generally comparable states of host T cell and myeloid cell depletion, the PC regimen was found to be highly immunosuppressive, as evidenced by a reduced host T cell capacity to secrete interleukin-2 and interferon-γ in vitro, to mediate host-versus-graft reactivity in vivo, and to recover numerically and functionally during a 2-week observation period after chemotherapy. Finally, using B6 hosts treated with the 14-day chemotherapy regimens, the PC regimen more consistently prevented the rejection of BALB/c T cell-depleted allografts compared with the FC regimen (rate of alloengraftment, 14/15 [93%] of PC-treated recipients vs 8/14 [57%] of FC-treated recipients; P < .05); similar results were observed using an 8-day conditioning regimen. These data suggest that host T cell suppression, distinct from T cell depletion, may be a critical determinant of engraftment after purine analog-based regimens and also may be preferentially attained by the use of pentostatin.

Assessing the Eventual Publication of Clinical Trial Abstracts Submitted to a Large Annual Oncology Meeting

BACKGROUND Despite the ethical imperative to publish clinical trials when human subjects are involved, such data frequently remain unpublished. The objectives were to tabulate the rate and ascertain factors associated with eventual publication of clinical trial results reported as abstracts in the Proceedings of the American Society of Clinical Oncology (American Society of Clinical Oncology). MATERIALS AND METHODS Abstracts describing clinical trials for patients with breast, lung, colorectal, ovarian, and prostate cancer from 2009 to 2011 were identified by using a comprehensive online database (http://meetinglibrary.asco.org/abstracts). Abstracts included reported results of a treatment or intervention assessed in a discrete, prospective clinical trial. Publication status at 4-6 years was determined by using a standardized search of PubMed. Primary outcomes were the rate of publication for abstracts of randomized and nonrandomized clinical trials. Secondary outcomes included factors influencing the publication of results. RESULTS A total of 1,075 abstracts describing 378 randomized and 697 nonrandomized clinical trials were evaluated. Across all years, 75% of randomized and 54% of nonrandomized trials were published, with an overall publication rate of 61%. Sample size was a statistically significant predictor of publication for both randomized and nonrandomized trials (odds ratio [OR] per increase of 100 participants = 1.23 [1.11-1.36], p < .001; and 1.64 [1.15-2.34], p = .006, respectively). Among randomized studies, an industry coauthor or involvement of a cooperative group increased the likelihood of publication (OR 2.37, p = .013; and 2.21, p = .01, respectively). Among nonrandomized studies, phase II trials were more likely to be published than phase I (p < .001). Use of an experimental agent was not a predictor of publication in randomized (OR 0.76 [0.38-1.52]; p = .441) or nonrandomized trials (OR 0.89 [0.61-1.29]; p = .532). CONCLUSION This is the largest reported study examining why oncology trials are not published. The data show that 4-6 years after appearing as abstracts, 39% of oncology clinical trials remain unpublished. Larger sample size and advanced trial phase were associated with eventual publication; among randomized trials, an industry-affiliated author or a cooperative group increased likelihood of publication. Unfortunately, we found that, despite widespread recognition of the problem and the creation of central data repositories, timely publishing of oncology clinical trials results remains unsatisfactory.

Multiplying therapies and reducing toxicity in metastatic melanoma

Prior to 2011, only 2 systemic treatments were approved for the treatment of melanoma and these had limited efficacy. In the past 4 years, 6 novel agents have received FDA approval. Herein, we will focus on 4 recently published NEJM papers reporting the results of clinical trials, comprising 4 agents targeting the MAPK pathway: the BRAF inhibitors vemurafenib and dabrafenib, and the MEK inhibitors trametinib and cobimetenib. These have been developed in parallel with a class of immunologic mediators often referred to as “immune checkpoint inhibitors.” These recent studies represent a marked acceleration of progress in the treatment of metastatic melanoma. While it was hoped that combining BRAF and MEK inhibitors would significantly mitigate drug resistance, such combinations have yielded only modestly better results than monotherapy. However, these combinations were successful in reducing the development of cutaneous squamous cell carcinomas and keratocanthomas. Therefore, combination therapies are clearly warranted. Thus far there are only limited data addressing the value of combinations of immunotherapeutic agents: a phase 1 trial of concurrent nivolumab plus ipilimumab suggested enhanced activity that may not depend on BRAF mutation status. Despite the attention and publicity given to the progress achieved in the therapy of melanoma, the majority of patients with metastatic disease still have a poor prognosis. Even novel combination regiments of BRAF and MEK inhibitors achieve complete response in only 13% of patients and a median PFS of 11.4 months in all patients. Better therapies remain desperately needed, especially for the 30–40% of patients with wild-type BRAF, for whom BRAF/MAPK inhibition offers no benefit. In the latter benefit is expected from emerging immunotherapies either singly or in combinations. The extent to which immunotherapies will add to regimens targeting BRAF remains to be determined.

ABC Transporters: Involvement in Multidrug Resistance and Drug Disposition

ATP-binding cassette (ABC) transporters, among the largest of the transporter superfamilies, are found in normal tissues and transport a wide range of substrates important in normal physiology. One normal tissue function of these transporters is protection from toxic compounds including xenobiotics. By limiting tissue exposure to substrates, ABC transporters may contribute to the blood–brain barrier, the maternal–fetal barrier, and the mucosal barrier that limits oral absorption of compounds. Because a range of chemotherapeutic drugs have been found to be substrates for several of these transporters, many have inferred that expression of transporters in tumor cells has the potential to confer drug resistance; indeed, several transporters are referred to as multidrug transporters. This chapter will review the role of these multidrug transporters in oncology and in normal tissue.

Rapamycin Resistant Murine Th9 Cells Have a Stable In Vivo Phenotype and Inhibit Graft-Versus-Host Reactivity

The cytokine micro-environment can direct murine CD4+ T cells towards various differentiation lineages such as Th1, Th2 and Tregs even in the presence of rapamycin, which results in T cells that mediate increased in vivo effects. Recently, a new lineage of T cells known as Th9 cells that secrete increased IL-9 have been described. However, it is not known whether Th9 differentiation occurs in the presence of rapamycin or whether adoptively transferred donor Th9 cells would augment or restrict alloreactivity after experimental bone marrow transplantation. We found that CD4+ T cells that were co-stimulated and polarized with TGF-β and IL-4 in the presence or absence of rapamycin each yielded effector cells of Th9 phenotype that secreted increased IL-9 and expressed a transcription factor profile characteristic of both Th9 and Th2 cells (high GATA-3/low T-bet). Augmentation of T cell replete allografts with manufactured rapamycin resistant Th9 cells markedly reduced both CD4+ and CD8+ T cell engraftment and strongly inhibited allo-specific T cell secretion of IFN-γ. The potency of Th9 cell inhibition of alloreactivity was similar to that of rapamycin resistant Th2 cells. Importantly, rapamycin resistant Th9 cells persisted and maintained their cytokine phenotype, thereby indicating limited differentiation plasticity of the Th9 subset. As such, Th9 differentiation proceeds in the presence of rapamycin to generate a cell therapy product that maintains high IL-9 expression in vivo while inhibiting IFN-γ driven alloreactivity.

CD30 positive atypical lymphocytes in perniosis: a potential histopathologic pitfall in a benign condition.

In classical clinical perniosis (chilblains), the presence of atypical lymphocytes with immunohistochemical staining positive for CD30 is unusual and rarely reported. Here we report 2 cases of clinical perniosis, one in a 16-year-old girl and another in a 67-year-old woman. The biopsies revealed lymphocytic infiltrates, papillary dermal edema, and atypical cells highlighted with a CD30 immunohistochemical stain. Our cases demonstrate the importance of clinicopathologic correlation in the assessment of CD30 positive lymphocytes in benign nonneoplastic conditions. Dermatopathologists must be aware of this potential histologic pattern in perniosis to prevent misdiagnosis and overtreatment of this condition.