PEGylated IL-10 (Pegilodecakin) Induces Systemic Immune Activation, CD8+ T Cell Invigoration and Polyclonal T Cell Expansion in Cancer Patients.

Tumor-reactive T cell exhaustion prevents the success of immune therapies. Pegilodecakin activates intratumoral CD8+ T cells in mice and induces objective tumor responses in patients. Here we report that pegilodecakin induces hallmarks of CD8+ T cell immunity in cancer patients, including elevation of interferon-γ and GranzymeB, expansion and activation of intratumoral CD8+ T cells, and proliferation and expansion of LAG-3+ PD-1+ CD8+ T cells. On pegilodecakin, newly expanded T cell clones, undetectable at baseline, become 1%-10% of the total T cell repertoire in the blood. Elevation of interleukin-18, expansion of LAG-3+ PD-1+ T cells and novel T cell clones each correlated with objective tumor responses. Combined pegilodecakin with anti-PD-1 increased the expansion of LAG-3+ PD-1+ CD8+ T cells.

PEG-rIL-10 treatment decreases FoxP3(+) Tregs despite upregulation of intratumoral IDO.

IL-10 has been classically defined as a broad-spectrum immunosuppressant and is thought to facilitate the development of regulatory CD4(+) T cells. IL-10 is believed to represent one of the major suppressive factors secreted by IDO(+)FoxP3(+)CD4(+) Tregs. Contrary to this view, we have previously reported that PEGylated recombinant IL-10 (PEG-rIL-10) treatment of mice induces potent IFNγ and CD8(+) T-cell-dependent antitumor immunity. This hypothesis is currently being tested in clinical trials and we have reported that treatment of cancer patients with PEG-rHuIL-10 results in inhibition and regression of tumor growth as well as increased serum IFNγ. We have continued to assess PEG-rIL-10's pleiotropic effects and report that treatment of tumor-bearing mice and humans with PEG-rIL-10 increases intratumoral indoleamine 2, 3-dioxygenase (IDO) in an IFNγ-dependent manner. This should result in an increase in Tregs, but paradoxically our data illustrate that PEG-rIL-10 treatment of mice reduces intratumoral FoxP3(+)CD4(+) T cells in an IDO-independent manner. Additional investigation indicates that PEG-rIL-10 inhibits TGFß/IL-2-dependent in vitro polarization of FoxP3(+)CD4(+) Tregs and potentiates IFNγ(+)T-bet(+)CD4(+) T cells. These data suggest that rather than acting as an immunosuppressant, PEG-rIL-10 may counteract the FoxP3(+)CD4(+) Treg suppressive milieu in tumor-bearing mice and humans, thereby further facilitating PEG-rIL-10's potent antitumor immunity.

PEGylated IL-10 Activates Kupffer Cells to Control Hypercholesterolemia.

Interleukin-10 (IL-10) is a multifunctional cytokine that exerts potent context specific immunostimulatory and immunosuppressive effects. We have investigated the mechanism by which PEGylated rIL-10 regulates plasma cholesterol in mice and humans. In agreement with previous work on rIL-10, we report that PEGylated rIL-10 harnesses the myeloid immune system to control total plasma cholesterol levels. We have discovered that PEG-rMuIL-10's dramatic lowering of plasma cholesterol is dependent on phagocytotic cells. In particular, PEG-rHuIL-10 enhances cholesterol uptake by Kupffer cells. In addition, removal of phagocytotic cells dramatically increases plasma cholesterol levels, suggesting for the first time that immunological cells are implicitly involved in regulating total cholesterol levels. These data suggest that treatment with PEG-rIL-10 potentiates endogenous cholesterol regulating cell populations not currently targeted by standard of care therapeutics. Furthermore, we show that IL-10's increase of Kupffer cell cholesterol phagocytosis is concomitant with decreases in liver cholesterol and triglycerides. This leads to the reversal of early periportal liver fibrosis and facilitates the restoration of liver health. These data recommend PEG-rIL-10 for evaluation in the treatment of fatty liver disease and preventing its progression to non-alcoholic steatohepatitis. In direct confirmation of our in vivo findings in the treatment of hypercholesterolemic mice with PEG-rMuIL-10, we report that treatment of hypercholesterolemic cancer patients with PEG-rHuIL-10 lowers total plasma cholesterol by up to 50%. Taken together these data suggest that PEG-rIL-10's cholesterol regulating biology is consistent between mice and humans.

Safety, Antitumor Activity, and Immune Activation of Pegylated Recombinant Human Interleukin-10 (AM0010) in Patients With Advanced Solid Tumors.

Purpose Interleukin-10 (IL-10) stimulates the expansion and cytotoxicity of tumor-infiltrating CD8+ T cells and inhibits inflammatory CD4+ T cells. Pegylation prolongs the serum concentration of IL-10 without changing the immunologic profile. This phase I study sought to determine the safety and antitumor activity of AM0010. Patients and Methods Patients with selected advanced solid tumors were treated with AM0010 in a dose-escalation study, which was followed by a renal cell cancer (RCC) dose-expansion cohort. AM0010 was self-administered subcutaneously at doses of 1 to 40 µg/kg once per day. Primary end points were safety and tolerability; clinical activity and immune activation were secondary end points. Results In the dose-escalation and -expansion cohorts, 33 and 18 patients, respectively, were treated with daily subcutaneous injection of AM0010. AM0010 was tolerated in a heavily pretreated patient population. Treatment-related adverse events (AEs) included anemia, fatigue, thrombocytopenia, fever, and injection site reactions. Grade 3 to 4 nonhematopoietic treatment-related AEs, including rash (n = 2) and transaminitis (n = 1), were observed in five of 33 patients. Grade 3 to 4 anemia or thrombocytopenia was observed in five patients. Most treatment-related AEs were transient or reversible. AM0010 led to systemic immune activation with elevated immune-stimulatory cytokines and reduced transforming growth factor beta in the serum. Partial responses were observed in one patient with uveal melanoma and four of 15 evaluable patients with RCC treated at 20 µg/kg (overall response rate, 27%). Prolonged stable disease of at least 4 months was observed in four patients, including one with colorectal cancer with disease stabilization for 20 months. Conclusion AM0010 has an acceptable toxicity profile with early evidence of antitumor activity, particularly in RCC. These data support the further evaluation of AM0010 both alone and in combination with other immune therapies and chemotherapies.

IL-10: Expanding the Immune Oncology Horizon.

Recent advances in immunoncology have dramatically changed the treatment options available to cancer patients. However, the fundamental challenges with this therapeutic modality are not new and still persist with the current wave of immunoncology compounds. These challenges are centered on the activation and expansion, induction of intratumoral infiltration and persistence of highly activated, cytotoxic, tumor antigen specific CD8+ T cells. We have investigated the anti-tumor mechanism of action of pegylated recombinant interleukin-10, (PEG-rIL-10) both pre-clinically with murine (PEG-rMuIL-10) and now clinically (AM0010) with human pegylated interleukin-10. The preponderance of data suggest that IL-10's engagement of its receptor on CD8+ T cells enhances their activation status leading to antigen specific expansion. Quantitation of CD8+ T cell tumor infiltration reveals that treatment of both humans and mice with pegylated rIL-10 results in 3-4 fold increases of intratumoral, cytotoxic, CD8+ T cells. In addition, mice cured of their tumors with PEG-rMuIL-10 exhibit long term immunological protection from tumor re-challenge and long term treatment of cancer patients with AM0010 results in the persistence of highly activated CD8+ T cells. Cumulatively, these data suggest the IL-10 represents an emerging therapeutic that specifically addresses the fundamental challenges of the current wave of immunoncology assets.

IL-10 directly activates and expands tumor-resident CD8(+) T cells without de novo infiltration from secondary lymphoid organs.

The presence of activated intratumoral T cells correlates clinically with better prognosis in patients with cancer. Although tumor vaccines can increase the number of tumor-specific CD8(+) T cells in systemic circulation, they frequently fail to increase the number of active and tumor reactive T cells within the tumor. Here we show that treatment with the pleiotropic cytokine interleukin-10 (IL-10) induces specific activation of tumor-resident CD8(+) T cells as well as their intratumoral expansion in several mouse tumor models. We found that inhibition of T-cell trafficking from lymphoid organs did not impair IL-10-induced tumor rejection or the activation of tumor-resident CD8(+) T cells. Tumor-resident CD8(+) T cells expressed elevated levels of the IL-10 receptor and were directly activated by IL-10, resulting in prominent phosphorylation of STAT3 and STAT1. Although CD4(+) T cells, regulatory T cells, NK cells, and dendritic cells have been reported as prominent targets of IL-10 in the tumor microenvironment, we found that expression of the IL-10R was required only on CD8(+) T cells to facilitate IL-10-induced tumor rejection as well as in situ expansion and proliferation of tumor-resident CD8 T cells. Together, our findings indicate that IL-10 activates CD8(+) T-cell-mediated tumor control and suggest that IL-10 may represent a potential tumor immunotherapy in human patients with cancer.

Mutant thyroid hormone receptors (TRs) isolated from distinct cancer types display distinct target gene specificities: a unique regulatory repertoire associated with two renal clear cell carcinomas.

Thyroid hormone receptors (TRs) are hormone-regulated transcription factors that regulate a diverse array of biological activities, including metabolism, homeostasis, and development. TRs also serve as tumor suppressors, and aberrant TR function (via mutation, deletion, or altered expression) is associated with a spectrum of both neoplastic and endocrine diseases. A particularly high frequency of TR mutations has been reported in renal clear cell carcinoma (RCCC) and in hepatocellular carcinoma (HCC). We have shown that HCC-TR mutants regulate only a fraction of the genes targeted by wild-type TRs but have gained the ability to regulate other, unique, targets. We have suggested that this altered gene recognition may contribute to the neoplastic phenotype. Here, to determine the generality of this phenomenon, we examined a distinct set of TR mutants associated with RCCC. We report that two different TR mutants, isolated from independent RCCC tumors, possess greatly expanded target gene specificities that extensively overlap one another, but only minimally overlap that of the wild-type TRs, or those of two HCC-TR mutants. Many of the genes targeted by either or both RCCC-TR mutants have been previously implicated in RCCC and include a series of metallothioneins, solute carriers, and genes involved in glycolysis and energy metabolism. We propose as a hypothesis that TR mutations from RCCC and HCC may play tissue-specific roles in carcinogenesis, and that the divergent target gene recognition patterns of TR mutants isolated from the two different types of tumors may arise from different selective pressures during development of RCCC vs. HCC.

A mechanism for pituitary-resistance to thyroid hormone (PRTH) syndrome: a loss in cooperative coactivator contacts by thyroid hormone receptor (TR)beta2.

Thyroid hormone receptors (TR) are hormone-modulated transcription factors that regulate overall metabolic rate, lipid utilization, heart rate, and development. TR are expressed as a mix of interrelated receptor isoforms. The TRß2 isoform is expressed in the hypothalamus and pituitary, where it plays an important role in the feedback regulation of thyroid hormone levels. TRß2 exhibits unique transcriptional properties that parallel the ability of this isoform to bind to certain coactivators cooperatively through multiple contact surfaces. The more peripherally expressed TRß1 isoform, in contrast, appears to recruit these coactivators through a single contact mechanism. We report here that clusters of charged amino acids in the TR hormone-binding domain are required for this enhanced mode of coactivator recruitment and that mutations in these charge clusters, by disrupting TRß2 coactivator binding, are a molecular basis for pituitary resistance to thyroid hormone, a disease characterized by inappropriate thyroid hormone feedback regulation. We propose that the charge clusters allow wild-type TRß2 to assume a conformation compatible with its mode of multiple contact coactivator recruitment, whereas disruption of these charge clusters disrupts normal T(3) homeostasis by reducing TRß2 to a TRß1-like, single contact mode of coactivator binding.

A conserved lysine in the thyroid hormone receptor-alpha1 DNA-binding domain, mutated in hepatocellular carcinoma, serves as a sensor for transcriptional regulation.

Nuclear receptors are hormone-regulated transcription factors that play key roles in normal physiology and development; conversely, mutant nuclear receptors are associated with a wide variety of neoplastic and endocrine disorders. Typically, these receptor mutants function as dominant negatives and can interfere with wild-type receptor activity. Dominant-negative thyroid hormone receptor (TR) mutations have been identified in over 60% of the human hepatocellular carcinomas analyzed. Most of these mutant TRs are defective for corepressor release or coactivator binding in vitro, accounting for their transcriptional defects in vivo. However, two HCC-TR mutants that function as dominant-negative receptors in cells display near-normal properties in vitro, raising questions about the molecular basis behind their transcriptional defects. We report here that a single amino acid substitution, located at the same position in the DNA-binding domain of both mutants, is responsible for their impaired transcriptional activation and dominant-negative properties. Significantly, this amino acid, K74 in TRalpha, is highly conserved in all known nuclear receptors and seems to function as an allosteric sensor that regulates the transcriptional activity of these receptors in response to binding to their DNA recognition sequences. We provide evidence that these two human hepatocellular carcinoma mutants have acquired dominant-negative function as a result of disruption of this allosteric sensing. Our results suggest a novel mechanism by which nuclear receptors can acquire transcriptional defects and contribute to neoplastic disease.

Isoform-specific transcriptional activity of overlapping target genes that respond to thyroid hormone receptors alpha1 and beta1.

Thyroid hormone receptors (TRs) are hormone-regulated transcription factors that control multiple aspects of physiology and development. TRs are expressed in vertebrates as a series of distinct isoforms that exert distinct biological roles. We wished to determine whether the two most widely expressed isoforms, TR alpha 1 and TR beta 1, exert their different biological effects by regulating different sets of target genes. Using stably transformed HepG2 cells and a microarray analysis, we were able to demonstrate that TR alpha 1 and TR beta 1 regulate a largely overlapping repertoire of target genes in response to T(3) hormone. However, these two isoforms display very different transcriptional properties on each individual target gene, ranging from a much greater T(3)-mediated regulation by TR alpha 1 than by TR beta 1, to near equal regulation by both isoforms. We also identified TR alpha 1 and TR beta 1 target genes that were regulated by these receptors in a hormone-independent fashion. We suggest that it is this gene-specific, isoform-specific amplitude of transcriptional regulation that is the likely basis for the appearance and maintenance of TR alpha 1 and TR beta 1 over evolutionary time. In essence, TR alpha 1 and TR beta 1 adjust the magnitude of the transcriptional response at different target genes to different levels; by altering the ratio of these isoforms in different tissues or at different developmental times, the intensity of T(3) response can be individually tailored to different physiological and developmental requirements.

The p160 coactivator PAS-B motif stabilizes nuclear receptor binding and contributes to isoform-specific regulation by thyroid hormone receptors.

Thyroid hormone receptors (TRs) are hormone-regulated transcription factors that play multiple roles in vertebrate endocrinology and development. TRs are expressed as a series of distinct receptor isoforms that mediate different biological functions. The TRbeta2 isoform is expressed primarily in the hypothalamus, pituitary, cochlea, and retina, and displays an enhanced response to hormone agonist relative to the other TR isoforms. We report here that the unusual transcriptional properties of TRbeta2 parallel the ability of this isoform to bind p160 coactivators cooperatively through multiple contact surfaces; the more broadly expressed TRbeta1 isoform, in contrast, utilizes a single contact mechanism. Intriguingly, the PAS-B domain in the p160 N terminus plays a previously unanticipated role in permitting TRbeta2 to recruit coactivator at limiting triiodothyronine concentrations. The PAS-B sequences also play an important role in coactivator binding by estrogen receptor-alpha. We propose that the PAS-B domain of the p160 coactivators is an important modulator of coactivator recruitment for a specific subset of nuclear receptors, permitting stronger transcriptional activation at lower hormone concentrations than would otherwise occur, and allowing isoform-specific mRNA splicing to customize the hormone response in different tissues.