DC-HIL+ CD14+ HLA-DR no/low cells are a potential blood marker and therapeutic target for melanoma

MDSC suppresses T cell antitumor immunity in CAC via GPNMB in a MyD88-dependent manner

BACKGROUND

Myeloid-derived suppressor cells (MDSCs) played an essential role in tumor microenvironment to suppress host antitumor immunity and help cancer cells escape immune surveillance. However, the molecular mechanism behind tumor evasion mediated by MDSCs is not fully understood. Glycoprotein nonmetastatic melanoma protein B (GPNMB) is considered to associate with tumor initiation, metastasis and angiogenesis. Blocking GPNMB function is a potentially valuable therapy for cancer by eliminating GPNMB+MDSCs. Our previous study has proved that blockage the MyD88 signaling with the MyD88 inhibitor, TJ-M2010-5, may completely prevent the development of CAC in mice, accompanying with downregulation of GPNMB mRNA in the inhibitor-treated mice of CAC.

METHODS

We here focus on the underlying the relationship between GPNMB function and MyD88 signaling pathway activation in MDSCs' antitumor activity in CAC.

RESULTS

CAC development in the mouse model is associated with expanded GPNMB+MDSCs by a MyD88-dependent pathway. The GPNMB expression on MDSCs is associated with MyD88 signaling activation. The inhibitory effect of MDSCs on T cell proliferation, activation and antitumor cytotoxicity in CAC is mediated by GPNMB in a MyD8-dependent manner.

CONCLUSION

MyD88 signaling pathway plays an essential role in GPNMB+MDSC-mediated tumor immune escape during CAC development and is a promising focus for revealing the mechanisms of MDSC that facilitate immunosuppression and tumor progression.

Inducible nitric oxide synthase-expressing myeloid-derived suppressor cells regulated by interleukin 35 contribute to the pathogenesis of psoriasis

Although psoriasis is classified as a T cell-mediated inflammatory disease, the contribution of myeloid cells to the pathogenesis of psoriasis is not fully understood. In the present study, we demonstrated that the expression of the anti-inflammatory cytokine interleukin-35 (IL-35) was significantly increased in patients with psoriasis with a marked increase in the number of myeloid-derived suppressor cells (MDSCs). Similar results were obtained in an imiquimod-induced psoriasis mouse model. IL-35 reduced the total number of MDSCs and their subtypes in the spleens and psoriatic skin lesions, ameliorating psoriasis. IL-35 also reduced the expression of inducible nitric oxide synthase in MDSCs, although it had no significant effect on interleukin-10 expression. Adoptive transfer of MDSCs from imiquimod-challenged mice aggravated the disease and weakened the effect of IL-35 in the recipient mice. In addition, mice transferred with MDSCs isolated from inducible nitric oxide synthase knockout mice had milder disease than those with wild-type MDSCs. Furthermore, wild-type MDSCs reversed the effects of IL-35, while MDSCs isolated from inducible nitric oxide synthase knockout mice did not affect IL-35 treatment. In summary, IL-35 may play a critical role in the regulation of iNOS-expressing MDSCs in the pathogenesis of psoriasis, highlighting IL-35 as a novel therapeutic strategy for patients with chronic psoriasis or other cutaneous inflammatory diseases.

GPNMB: a potent inducer of immunosuppression in cancer

The immune system is comprised of both innate and adaptive immune cells, which, in the context of cancer, collectively function to eliminate tumor cells. However, tumors can actively sculpt the immune landscape to favor the establishment of an immunosuppressive microenvironment, which promotes tumor growth and progression to metastatic disease. Glycoprotein-NMB (GPNMB) is a transmembrane glycoprotein that is overexpressed in a variety of cancers. It can promote primary tumor growth and metastasis, and GPNMB expression correlates with poor prognosis and shorter recurrence-free survival in patients. There is growing evidence supporting an immunosuppressive role for GPNMB in the context of malignancy. This review provides a description of the emerging roles of GPNMB as an inducer of immunosuppression, with a particular focus on its role in mediating cancer progression by restraining pro-inflammatory innate and adaptive immune responses.

Adaptive resistance in tumors to anti-PD-1 therapy through re-immunosuppression by upregulation of GPNMB expression

Acquired resistance to the antitumor activity of antibodies targeting the programmed death 1 (PD-1): programmed death ligand 1 (PD-L1) immune checkpoint in various types of cancers has increasingly been observed during treatment. To gain insight into the molecular mechanism underlying anti-PD-1 therapy resistance, we developed a mouse MC38 colon adenocarcinoma cell line that was made resistant to anti-PD-1 treatment through repeated in vivo selection. We compared the transcriptomic profiles of anti-PD-1 therapy-resistant and -sensitive tumors using RNA sequencing analysis. The immunosuppressive molecule transmembrane glycoprotein NMB (GPNMB) was significantly upregulated in resistant tumor cells, as determined using quantitative real-time polymerase chain reaction and immunofluorescence analyses. Furthermore, deletion of GPNMB in resistant cells successfully restored sensitivity to anti-PD-1 treatment in vivo. Collectively, our results indicate that tumors may develop resistance to anti-PD-1 therapy by upregulating their expression of the immunosuppressive molecule GPNMB. Furthermore, GPNMB is a potential, targetable biomarker for monitoring adaptive resistance to therapeutic PD-1 blockade, and identification of this immunosuppressive molecule may be a breakthrough for new therapies.

Circulating CD14+HLA-DR-/low Myeloid-Derived Suppressor Cells as Potential Biomarkers for the Identification of Psoriasis TCM Blood-Heat Syndrome and Blood-Stasis Syndrome

Psoriasis is a chronic autoimmune disease. Identification of the biomarkers responsible for Traditional Chinese Medicine (TCM) syndromes of psoriasis can help researchers recognize the different aspects of psoriasis and find novel therapeutic targets for the treatment of psoriasis. The current study investigated the levels of circulating Mo-MDSCs and Mo-MDSC-associated immune factors in the peripheral blood of psoriasis patients with different TCM syndromes. We found that the frequency of Mo-MDSCs (CD14⁺HLA-DR^−/low cells) among CD14⁺ cells from plaque psoriasis patients with blood-stasis (BS) syndrome was significantly increased when compared with healthy controls (p < 0.001) and blood-heat (BH) syndrome group (p < 0.001), respectively. However, serum IL-2, IL-4, IL-6, IL-10, IL-17A, TNF-α, IFN-γ, iNOS, Arg-1, and NO concentration showed no statistically significant difference between healthy controls and psoriasis patients as well as no significant difference between the BH and BS syndrome groups. Compared with healthy controls, the mRNA expression of Arg-1, TNF-α, ROR-γ, and PD-L1 was increased, while the mRNA expression of PD-1 and IL-10 was decreased in PBMCs from psoriasis patients. Moreover, the mRNA expression of TNF-α and FOXP3 in PBMCs showed a pronounced statistical difference between the psoriatic BH syndrome group and the BS syndrome group. Therefore, we provide evidence that the percentage of CD14⁺HLA-DR^−/low MDSC/ CD14⁺ cells and TNF-α and Foxp3 mRNA expression levels in PBMCs are potential biomarkers for distinguishing TCM BH syndrome and BS syndrome.

Blocking Monocytic Myeloid-Derived Suppressor Cell Function via Anti-DC-HIL/GPNMB Antibody Restores the In Vitro Integrity of T Cells from Cancer Patients

PURPOSE

Blocking the function of myeloid-derived suppressor cells (MDSC) is an attractive approach for cancer immunotherapy. Having shown DC-HIL/GPNMB to be the T-cell-inhibitory receptor mediating the suppressor function of MDSCs, we evaluated the potential of anti-DC-HIL mAb as an MDSC-targeting cancer treatment.

EXPERIMENTAL DESIGN

Patients with metastatic cancer (n = 198) were analyzed by flow cytometry for DC-HIL or PDL1 expression on blood CD14+HLA-DRno/lo MDSCs. Their suppressor function was assessed by in vitro coculture with autologous T cells, and the ability of anti-DC-HIL or anti-PDL1 mAb to reverse such function was determined. Tumor expression of these receptors was examined histologically, and the antitumor activity of the mAb was evaluated by attenuated growth of colon cancers in mice.

RESULTS

Patients with metastatic cancer had high blood levels of DC-HIL+ MDSCs compared with healthy controls. Anti-DC-HIL mAb reversed the in vitro function in ∼80% of cancer patients tested, particularly for colon cancer. Despite very low expression on blood MDSCs, anti-PDL1 mAb was as effective as anti-DC-HIL mAb in reversing MDSC function, a paradoxical phenomenon we found to be due to upregulated expression of PDL1 by T-cell-derived IFNγ in cocultures. DC-HIL is not expressed by colorectal cancer cells but by CD14+ cells infiltrating the tumor. Finally, anti-DC-HIL mAb attenuated growth of preestablished colon tumors by reducing MDSCs and increasing IFNγ-secreting T cells in the tumor microenvironment, with similar outcomes to anti-PDL1 mAb.

CONCLUSIONS

Blocking DC-HIL function is a potentially useful treatment for at least colorectal cancer with high blood levels of DC-HIL+ MDSCs.See related commentary by Colombo, p. 453.

Expanding the List of Dysregulated Immunosuppressive Cells in Psoriasis

Traditionally, myeloid-derived suppressor cells (MDSC) have been studied in regard to their increased numbers of circulating cells in cancer patients. Recent research efforts have also increased awareness of MDSC in non-malignant inflammatory diseases, including asthma, inflammatory bowel disease, and arthritis. Psoriasis can now be added to the growing list of inflammatory disorders with an MDSC component. Cao et al. report increased numbers of monocytic myeloid-derived suppressor cells (Mo-MDSC) in psoriasis patients and examine the implication of dysregulated Mo-MDSC function. Cao et al. describe psoriatic Mo-MDSC that produce increased IL-23, IL-1b, and CCL4 cytokines compared to Mo-MDSC from healthy controls. These results complement previous research demonstrating psoriatic Mo-MDSC are unable to suppress autologous and heterologous CD8 T-cell proliferations, display decreased expression levels of PD-1 as well as PD-L1, and fail to produce effective immuno-competent regulatory T cells (Tregs). Cao et al. also identify the unique expression of the surface protein DC-HIL on psoriatic Mo-MDSC. The expanded population of DC-HIL(+) Mo-MDSC in psoriasis patients, however, display inferior suppressive capabilities compared to DC-HIL(+) Mo-MDSC found in melanoma patients, suggesting contextual signaling as a potential contributing factor to Mo-MDSC function.

Targeting GPNMB with glembatumumab vedotin: Current developments and future opportunities for the treatment of cancer

GPNMB has emerged as an immunomodulator and an important positive mediator of tumor progression and metastasis in numerous solid cancers. Tumor intrinsic GPNMB-mediated effects on cellular signaling, coupled with the ability of GPNMB to influence the primary tumor and metastatic microenvironments in a non-cell autonomous fashion, combine to augment malignant cancer phenotypes. In addition, GPNMB is often overexpressed in a variety of cancers, making it an attractive therapeutic target. In this regard, glembatumumab vedotin, an antibody-drug conjugate (ADC) that targets GPNMB, is currently in clinical trials as a single agent in multiple cancers. In this review, we will describe the physiological functions of GPNMB in normal tissues and summarize the processes through which GPNMB augments tumor growth and metastasis. We will review the pre-clinical and clinical development of glembatumumab vedotin, evaluate on-going clinical trials, explore emerging opportunities for this agent in new disease indications and discuss exciting possibilities for this ADC in the context of combination therapies.

Myeloid-Derived Suppressor Cells in Psoriasis Are an Expanded Population Exhibiting Diverse T-Cell-Suppressor Mechanisms

Psoriasis vulgaris is an inflammatory skin disease caused by hyperactivated T cells regulated by positive and negative mechanisms; although the former have been much studied, the latter have not. We studied the regulatory mechanism mediated by myeloid-derived suppressor cells (MDSCs) and showed that MDSCs expanded in melanoma patients express dendritic cell-associated heparan sulfate proteoglycan-dependent integrin ligand, a critical mediator of T-cell suppressor function. We examined expansion of DC-HIL(+) MDSCs in psoriasis and characterized their functional properties. Frequency of DC-HIL(+) monocytic MDSCs (CD14(+)HLA-DR(no/low)) in blood and skin was markedly increased in psoriatic patients versus healthy control subjects, but there was no statistically significant relationship with disease severity (based on Psoriasis Area and Severity Index score). Blood DC-HIL(+) MDSC levels in untreated patients were significantly higher than in treated patients. Compared with melanoma-derived MDSCs, psoriatic MDSCs exhibited significantly reduced suppressor function and were less dependent on DC-HIL, but they were capable of inhibiting proliferation and IFN-γ and IL-17 responses of autologous T cells. Psoriatic MDSCs were functionally diverse among patients in their ability to suppress allogeneic T cells and in the use of either IL-17/arginase I or IFN-γ/inducible nitric oxide synthase axis as suppressor mechanisms. Thus, DC-HIL(+) MDSCs are expanded in psoriasis patients, and their mechanistic heterogeneity and relative functional deficiency may contribute to the development of psoriasis.