Soluble CD27 as a predictive biomarker for intra-tumoral CD70/CD27 interaction in nasopharyngeal carcinoma

In CD70-expressing tumors, the interaction of CD70 on tumor cells with its lymphocyte receptor, CD27, is thought to play a role in immunosuppression in the tumor microenvironment and elevated serum levels of soluble CD27 (sCD27). Previous studies showed that CD70 is expressed in nasopharyngeal carcinoma (NPC), an Epstein-Barr virus (EBV)-related malignancy. However, the association between intratumoral CD70/CD27 expression and serum levels of sCD27 in NPC remains unclear. In the present study, we show that CD70 is primarily expressed by tumor cells in NPC and that CD27-positive lymphocytes infiltrate around tumor cells. NPC patients with CD27-positive lymphocytes had significantly better prognosis than patients lacking these cells. In addition, high CD70 expression by tumor cells tended to be correlated with shorter survival in NPC patients with CD27-positive lymphocytes. Serum sCD27 levels were significantly increased in patients with NPC and provided good diagnostic accuracy for discriminating patients from healthy individuals. The concentration of serum sCD27 in patients with CD70-positive NPC with CD27-positive lymphocytes was significantly higher than in patients with tumors negative for CD70 and/or CD27, indicating that the intratumoral CD70/CD27 interaction boosts the release of sCD27. Furthermore, positive expression of CD70 by NPC cells was significantly correlated with EBV infection. Our results suggest that CD70/CD27-targeted immunotherapies may be promising treatment options and that sCD27 may become an essential tool for evaluating the applicability of these therapies by predicting the intratumoral CD70/CD27 interaction in NPC.

Erratum: Deep convolutional neural networks-based scatterer density and resolution estimators in optical coherence tomography: erratum

[This corrects the article on p. 168 in vol. 13, PMID: 35154862.].

Collision tumor of spindle cell lipoma arising from perirenal tissue and acquired cystic disease-associated renal cell carcinoma: A rare case report

Introduction

Collision tumors are a rare phenomenon defined as two or more histologically distinct tumors that are in contact with each other.

Case presentation

The patient was a man with a history of end-stage diabetic nephropathy under hemodialysis treatment for 15 years. A plain computed tomography scan showed a 4.3 cm mass with obscured margins in the right perirenal fat of the lower pole kidney. On T2-weighted magnetic resonance imaging, the lesion showed heterogeneous signal intensity with a partially cystic component. A radical nephrectomy was performed. Histopathological and immunohistochemical examination revealed collision tumors constituted of a spindle cell lipoma covering the kidney surface underneath the perirenal fat and diffusely distributed acquired cystic disease-associated renal cell carcinoma in the renal parenchyma.

Conclusion

We report the first case of collision tumors comprising spindle cell lipoma and acquired cystic disease-associated renal cell carcinoma.

Celecoxib promotes the efficacy of STING-targeted therapy by increasing antitumor CD8+ T-cell functions via modulating glucose metabolism of CD11b+ Ly6G+ cells

Recent studies have shown that activation of the cGAS-STING pathway is a key process in antitumor immune responses and various kinds of STING agonists have been developed for cancer immunotherapy. Despite promising preclinical studies, preliminary clinical results have shown only a modest effect of STING agonists. There is therefore a need to develop more effective treatment strategies. Based on previous observations that COX-2 is frequently overexpressed not only in a variety of cancers but also in tumor myeloid cells and that it suppresses antitumor immunity and promotes tumor survival by producing PGE2, we investigated the antitumor effects of combination therapy with a STING agonist cGAMP and the selective COX-2 inhibitor celecoxib in mouse models. Combination treatment with cGAMP and celecoxib inhibited tumor growth compared with either monotherapy, and the combination therapy induced both local and systemic antitumor immunity. cGAMP treatment decreased PD-1 expression on tumor-infiltrating T-cells and enhanced T-cell activation in tumor-draining lymph nodes regardless of the presence of celecoxib. Meanwhile, although celecoxib treatment did not alter the frequency of CD4⁺ CD25⁺ Foxp3⁺ regulatory T-cells, it enhanced the expression of costimulatory molecules and glycolysis-associated genes in tumor-infiltrating CD11b⁺ Ly6G⁺ cells. Moreover, we also found that celecoxib decreased lactate efflux and increased the frequency of IFN-γ- and TNF-α-producing CD8⁺ T-cells in the tumor microenvironment. Taken together, our findings suggest that combined treatment with celecoxib may be an effective strategy to improve the antitumor efficacy of STING agonists.

Expression of soluble CD27 in extranodal natural killer/T-cell lymphoma, nasal type: potential as a biomarker for diagnosis and CD27/CD70-targeted therapy

The engagement of CD27 on lymphocytes with its ligand, CD70, on tumors is believed to mediate tumor immune evasion and the elevation of serum soluble CD27 (sCD27) levels in patients with CD70-positive malignancies. We previously showed that CD70 is expressed in extranodal natural killer/T-cell lymphoma, nasal type (ENKL), an Epstein-Barr virus (EBV)-related malignancy. However, little is known about serum sCD27 expression and its association with the clinical characteristics of, and the CD27/CD70 interaction in, ENKL. In the present study, we show that serum sCD27 is significantly elevated in the sera of patients with ENKL. The levels of serum sCD27 provided excellent diagnostic accuracy for discriminating patients with ENKL from healthy subjects, correlated positively with the levels of other diagnostic markers (lactate dehydrogenase, soluble interleukin-2 receptor, and EBV-DNA), and decreased significantly following treatment. Elevated serum sCD27 levels also correlated significantly with advanced clinical stage and tended to correspond with shorter survival, in patients with ENKL. Immunohistochemistry indicated that CD27-positive tumor-infiltrating immune cells exist adjacent to CD70-positive lymphoma cells. In addition, serum sCD27 levels in patients with CD70-positive ENKL were significantly higher than those in patients with CD70-negative ENKL, suggesting that the intra-tumoral CD27/CD70 interaction boosts the release of sCD27 in serum. Furthermore, the EBV-encoded oncoprotein latent membrane protein 1 upregulated CD70 expression in ENKL cells. Our results suggest that sCD27 may serve as a novel diagnostic biomarker and also may serve as a tool for evaluating the applicability of CD27/CD70-targeted therapies by predicting intra-tumoral CD70 expression and CD27/CD70 interaction in ENKL.

Erratum: Computational refocusing of Jones matrix polarization-sensitive optical coherence tomography and investigation of defocus-induced polarization artifacts: publisher's note

[This corrects the article on p. 2975 in vol. 13.].

A tumor metastasis-associated molecule TWIST1 is a favorable target for cancer immunotherapy due to its immunogenicity

Although neoantigens are one of the most favorable targets in cancer immunotherapy, it is less versatile and costly to apply neoantigen-derived cancer vaccines to patients due to individual variation. It is, therefore, important to find highly immunogenic antigens among tumor-specific or associated antigens, which are shared among patients. Considering the cancer immunoediting theory, immunogenic tumor cells cannot survive in early phase of tumor progression including two processes: elimination and equilibrium. We hypothesized that highly immunogenic molecules are allowed to be expressed in tumor cells after immune suppressive tumor microenvironment was established, if these molecules contribute to tumor survival. In the current study, we focused on TWIST1 as a candidate of highly immunogenic antigens because it is upregulated in tumor cells under hypoxia and promotes tumor metastasis, which are observed in late phase of tumor progression. We demonstrated that TWIST1 had an immunogenic peptide sequence TWIST1_140-162 , which effectively activated TWIST1-specific CD4⁺ T-cells. In a short-term culture system, we detected more TWIST1-specific responses in breast cancer patients than in healthy donors. Vaccination with the TWIST1 peptide also showed efficient expansion of TWIST1-reactive HTLs in humanized mice. These findings indicate that TWIST1 is a highly immunogenic shared antigen and a favorable target for cancer immunotherapy.

Computational refocusing of Jones matrix polarization-sensitive optical coherence tomography and investigation of defocus-induced polarization artifacts

Here we demonstrate a long-depth-of-focus imaging method using polarization sensitive optical coherence tomography (PS-OCT). This method involves a combination of Fresnel-diffraction-model-based phase sensitive computational refocusing and Jones-matrix based PS-OCT (JM-OCT). JM-OCT measures four complex OCT images corresponding to four polarization channels. These OCT images are computationally refocused as preserving the mutual phase consistency. This method is validated using a static phantom, postmortem zebrafish, and ex vivo porcine muscle samples. All the samples demonstrated successful computationally-refocused birefringence and degree-of-polarization-uniformity (DOPU) images. We found that defocusing induces polarization artifacts, i.e., incorrectly high birefringence values and low DOPU values, which are substantially mitigated by computational refocusing.

Deep convolutional neural network-based scatterer density and resolution estimators in optical coherence tomography

We present deep convolutional neural network (DCNN)-based estimators of the tissue scatterer density (SD), lateral and axial resolutions, signal-to-noise ratio (SNR), and effective number of scatterers (ENS, the number of scatterers within a resolution volume). The estimators analyze the speckle pattern of an optical coherence tomography (OCT) image in estimating these parameters. The DCNN is trained by a large number (1,280,000) of image patches that are fully numerically generated in OCT imaging simulation. Numerical and experimental validations were performed. The numerical validation shows good estimation accuracy as the root mean square errors were 0.23%, 3.65%, 3.58%, 3.79%, and 6.15% for SD, lateral and axial resolutions, SNR, and ENS, respectively. The experimental validation using scattering phantoms (Intralipid emulsion) shows reasonable estimations. Namely, the estimated SDs were proportional to the Intralipid concentrations, and the average estimation errors of lateral and axial resolutions were 1.36% and 0.68%, respectively. The scatterer density estimator was also applied to an in vitro tumor cell spheroid, and a reduction in the scatterer density during cell necrosis was found.

CD47 blockade enhances the efficacy of intratumoral STING-targeting therapy by activating phagocytes

Activation of STING signaling plays an important role in anti-tumor immunity, and we previously reported the anti-tumor effects of STING through accumulation of M1-like macrophages in tumor tissue treated with a STING agonist. However, myeloid cells express SIRPα, an inhibitory receptor for phagocytosis, and its receptor, CD47, is overexpressed in various cancer types. Based on our findings that breast cancer patients with highly expressed CD47 have poor survival, we evaluated the therapeutic efficacy and underlying mechanisms of combination therapy with the STING ligand cGAMP and an antagonistic anti-CD47 mAb using E0771 mouse breast cancer cells. Anti-CD47 mAb monotherapy did not suppress tumor growth in our setting, whereas cGAMP and anti-CD47 mAb combination therapy inhibited tumor growth. The combination therapy enhanced phagocytosis of tumor cells and induced systemic anti-tumor immune responses, which rely on STING and type I IFN signaling. Taken together, our findings indicate that coadministration of cGAMP and an antagonistic anti-CD47 mAb may be promising for effective cancer immunotherapy.

SMARCB1 (INI1) retained but SMARCA4 (BRG1) negative atypical teratoid/rhabdoid tumor arising at the bilateral cerebellopontine angles: a case report

Most atypical teratoid/rhabdoid tumor (AT/RT) of the central nervous system shows an inactivation of SMARCB1 (INI1) and is considered as the hallmark of this neoplasm. However, AT/RT could exceptionally rarely present retained SMARCB1 (INI1) but inactivated SMARCA4 (BRG1). Here, the authors report a rare case of a 2-year-old boy with a SMARCB1 (INI1) retained but SMARCA4 (BRG1) negative AT/RT arising at the bilateral cerebellopontine angles mimicking neurofibromatosis type 2. The tumor was highly aggressive and was refractory to all treatment modalities. This case highlights the challenges during differential diagnosis of atypical cerebellopontine angle tumors of childhood and the importance of thoroughly investigating SMARCB1 (INI1) and SMARCA4 (BRG1) when AT/RT is suspected.

Computational multi-directional optical coherence tomography for visualizing the microstructural directionality of the tissue

We demonstrate computational multi-directional optical coherence tomography (OCT) to assess the directional property of tissue microstructure. This method is the combination of phase-sensitive volumetric OCT imaging and post-signal processing. The latter comprises of two steps. The first step is an intensity-directional analysis, which determines the dominant en face fiber orientations. The second step is the phase-directional imaging, which reveals the sub-resolution depth-orientation of the microstructure. The feasibility of the method was tested by assessing muscle and tendon samples. Stripe patterns with several sizes were visualized in the phase-directional images. In order to interpret these images, the muscle and tendon structures were numerically modeled, and the phase-directional images were generated from the numerical model. The similarity of the experimental and numerical results suggested that the stripe patterns correspond to the muscle fiber bundle and its crimping.

A stealth antigen SPESP1, which is epigenetically silenced in tumors, is a suitable target for cancer immunotherapy

Recent studies have revealed that tumor cells decrease their immunogenicity by epigenetically repressing the expression of highly immunogenic antigens to survive in immunocompetent hosts. We hypothesized that these epigenetically hidden “stealth” antigens should be favorable targets for cancer immunotherapy due to their high immunogenicity. To identify these stealth antigens, we treated human lung cell line A549 with DNA methyltransferase inhibitor 5‐aza‐2′‐deoxycytidine (5Aza) and its prodrug guadecitabine for 3 d in vitro and screened it using cDNA microarray analysis. We found that the gene encoding sperm equatorial segment protein 1 (SPESP1) was re‐expressed in cell lines including solid tumors and leukemias treated with 5Aza, although SPESP1 was not detected in untreated tumor cell lines. Using normal human tissue cDNA panels, we demonstrated that SPESP1 was not detected in normal human tissue except for testis and placenta. Moreover, we found using immunohistochemistry SPESP1 re‐expression in xenografts in BALB/c‐nu/nu mice that received 5Aza treatment. To assess the antigenicity of SPESP1, we stimulated human CD4⁺ T‐cells with a SPESP1‐derived peptide designed using a computer algorithm. After repetitive stimulation, SPESP1‐specific helper T‐cells were obtained; these cells produced interferon‐γ against HLA‐matched tumor cell lines treated with 5Aza. We also detected SPESP1 expression in freshly collected tumor cells derived from patients with acute myeloid leukemia or lung cancer. In conclusion, SPESP1 can be classified as a stealth antigen, a molecule encoded by a gene that is epigenetically silenced in tumor cells but serves as a highly immunogenic antigen suitable for cancer immunotherapy.

A critical role of STING-triggered tumor-migrating neutrophils for anti-tumor effect of intratumoral cGAMP treatment

Stimulator of interferon genes (STING) contributes to anti-tumor immunity by activating antigen-presenting cells and inducing mobilization of tumor-specific T cells. A role for tumor-migrating neutrophils in the anti-tumor effect of STING-activating therapy has not been defined. We used mouse tumor transplantation models for assessing neutrophil migration into the tumor triggered by intratumoral treatment with STING agonist, 2'3'-cyclic guanosine monophosphate-adenosine monophosphate (cGAMP). Intratumoral STING activation with cGAMP enhanced neutrophil migration into the tumor in an NF-κB/CXCL1/2-dependent manner. Blocking the neutrophil migration by anti-CXCR2 monoclonal antibody impaired T cell activation in tumor-draining lymph nodes (dLNs) and efficacy of intratumoral cGAMP treatment. Moreover, the intratumoral cGAMP treatment did not show any anti-tumor effect in type I interferon (IFN) signal-impaired mice in spite of enhanced neutrophil accumulation in the tumor. These results suggest that both neutrophil migration and type I interferon (IFN) induction by intratumoral cGAMP treatment were critical for T-cell activation of dLNs and the anti-tumor effect. In addition, we also performed in vitro analysis showing enhanced cytotoxicity of neutrophils by IFN-β1. Extrinsic STING activation triggers anti-tumor immune responses by recruiting and activating neutrophils in the tumor via two signaling pathways, CXCL1/2 and type I IFNs.

Expression of placenta-specific 1 and its potential for eliciting anti-tumor helper T-cell responses in head and neck squamous cell carcinoma

Placenta-specific 1 (PLAC1) is expressed primarily in placental trophoblasts but not in normal tissues and is a targetable candidate for cancer immunotherapy because it is a cancer testis antigen known to be up-regulated in various tumors. Although peptide epitopes capable of stimulating CD8 T cells have been previously described, there have been no reports of PLAC1 CD4 helper T lymphocyte (HTL) epitopes and the expression of this antigen in head and neck squamous cell carcinoma (HNSCC). Here, we show that PLAC1 is highly expressed in 74.5% of oropharyngeal and 51.9% of oral cavity tumors from HNSCC patients and in several HNSCC established cell lines. We also identified an HTL peptide epitope (PLAC1_31-50) capable of eliciting effective antigen-specific and tumor-reactive T cell responses. Notably, this peptide behaves as a promiscuous epitope capable of stimulating T cells in the context of more than one human leukocyte antigen (HLA)-DR allele and induces PLAC1-specific CD4 T cells that kill PLAC1-positive HNSCC cell lines in an HLA-DR-restricted manner. Furthermore, T-cells reactive to PLAC1_31-50 peptide were detected in the peripheral blood of HNSCC patients. These findings suggest that PLAC1 represents a potential target antigen for HTL based immunotherapy in HNSCC.

Bulk-phase-error correction for phase-sensitive signal processing of optical coherence tomography

We present a numerical phase stabilization method for phase-sensitive signal processing of optical coherence tomography (OCT). This method removes the bulk phase error caused by the axial bulk motion of the sample and the environmental perturbation during volumetric acquisition. In this method, the partial derivatives of the phase error are computed along both fast and slow scanning directions, so that the vectorial gradient field of the phase error is given. Then, the phase error is estimated from the vectorial gradient field by a newly developed line integration method; a smart integration path method. The performance of this method was evaluated by analyzing the spatial frequency spectra of en face OCT images, and it objectively shows the significant phase-error-correction ability of the method. The performance was also evaluated by observing computationally refocused en face images of ex vivo tissue samples, and it was found that the image quality was improved by the phase-error correction.

Phosphorylated vimentin as an immunotherapeutic target against metastatic colorectal cancer

Colorectal cancer (CRC) patients with metastatic lesions have low 5-year survival rates. During metastasis, cancer cells often obtain unique characteristics such as epithelial-mesenchymal transition (EMT). Vimentin a biomarker contributes to EMT by changing cell shape and motility. Since abnormal phosphorylation is a hallmark of malignancy, targeting phosphorylated vimentin is a feasible approach for the treatment of metastatic tumors while sparing non-tumor cells. Recent evidence has revealed that both CD8 cytotoxic T lymphocytes (CTLs) and also CD4 helper T lymphocytes (HTLs) can distinguish post-translationally modified antigens from normal antigens. Here, we showed that the expression of phosphorylated vimentin was upregulated in metastatic sites of CRC. We also showed that a chemotherapeutic reagent augmented the expression of phosphorylated vimentin. The novel phosphorylated helper peptide epitopes from vimentin could elicit a sufficient T cell response. Notably, precursor lymphocytes that specifically reacted to these phosphorylated vimentin-derived peptides were detected in CRC patients. These results suggest that immunotherapy targeting phosphorylated vimentin could be promising for metastatic CRC patients.

Intratumoral STING activations overcome negative impact of cisplatin on antitumor immunity by inflaming tumor microenvironment in squamous cell carcinoma

Although cisplatin (CDDP) has been used as a major chemotherapeutic drug for head and neck squamous cell carcinoma (HNSCC), its impact on T-cell functions is controversial. Therefore, we investigated the immunologic effects of CDDP and antitumor effects by combination therapy of CDDP with a ligand for stimulator of interferon genes, cyclic guanosine monophosphate-adenosine monophosphate (cGAMP). Direct impacts of CDDP on T-cell functions were addressed by comparing T-cell functions between human subjects treated and untreated with CDDP. The immune responses and the efficacy of combination therapy using CDDP and cGAMP were assessed using BALB/c mice inoculated with mouse squamous cell carcinoma (SCC) cell lines. CDDP inhibited T-cell proliferation in a dose-dependent manner. T-cell functions of CDDP-treated HNSCC patients were comparable to those of healthy donors and CDDP-untreated HNSCC patients. In the mice bearing SCC cell lines, combination therapy using CDDP and cGAMP enhanced the gene expressions of CXCL9 and CXCL10 in the tumor tissues and inhibited tumor growth. The antitumor effect was cancelled by anti-CXCR3 monoclonal antibody. These findings suggest that the combination therapy using CDDP and an immunomodulating drug like cGAMP would be a rational cancer immunotherapy for patients with HNSCC.

PD-L1-specific helper T-cells exhibit effective antitumor responses: new strategy of cancer immunotherapy targeting PD-L1 in head and neck squamous cell carcinoma

BACKGROUND

Head and neck squamous cell carcinoma (HNSCC) originates from squamous epithelium of the upper aerodigestive tract and is the most common malignancy in the head and neck region. Among HNSCCs, oropharynx squamous cell carcinoma (OSCC) has a unique profile and is associated with human papillomavirus infection. Recently, anti-programmed cell death-1 monoclonal antibody has yielded good clinical responses in recurrent and/or metastatic HNSCC patients. Therefore, programmed death-ligand 1 (PD-L1) may be a favorable target molecule for cancer immunotherapy. Although PD-L1-expressing malignant cells could be targeted by PD-L1-specific CD8⁺ cytotoxic T lymphocytes, it remains unclear whether CD4⁺ helper T lymphocytes (HTLs) recognize and kill tumor cells in a PD-L1-specific manner.

METHODS

The expression levels of PD-L1 and HLA-DR were evaluated using immunohistochemical analyses. MHC class II-binding peptides for PD-L1 were designed based on computer algorithm analyses and added into in vitro culture of HTLs with antigen-presenting cells to evaluate their stimulatory activity.

RESULTS

We found that seven of 24 cases of OSCC showed positive for both PD-L1 and HLA-DR and that PD-L1_241-265 peptide efficiently activates HTLs, which showed not only cytokine production but also cytotoxicity against tumor cells in a PD-L1-dependent manner. Also, an adoptive transfer of the PD-L1-specific HTLs significantly inhibited growth of PD-L1-expressing human tumor cell lines in an immunodeficient mouse model. Importantly, T cell responses specific for the PD-L1_241-265 peptide were detected in the HNSCC patients.

CONCLUSIONS

The cancer immunotherapy targeting PD-L1 as a helper T-cell antigen would be a rational strategy for HNSCC patients.

Targeting phosphorylated p53 to elicit tumor-reactive T helper responses against head and neck squamous cell carcinoma

The human T cell receptor is capable of distinguishing between normal and post-translationally modified peptides. Because aberrant phosphorylation of cellular proteins is a hallmark of malignant transformation, the expression of the phosphorylated epitope could be an ideal antigen to combat cancer without damaging normal tissues. p53 activates transcription factors to suppress tumors by upregulating growth arrest and apoptosis-related genes. In response to DNA damage, p53 is phosphorylated at multiple sites including Ser33 and Ser37. Here, we identified phosphorylated peptide epitopes from p53 that could elicit effective T helper responses. These epitope peptides, p53_{22-41/Phospho-S33} and p53_{22-41/Phospho-S37}, induced T helper responses against tumor cells expressing the phosphorylated p53 protein. Moreover, chemotherapeutic agents augmented the responses of such CD4 T cells via upregulation of phosphorylated p53. The upregulation of phosphorylated p53 expression by chemotherapy was confirmed in in vitro and xenograft models. We evaluated phosphorylated p53 expression in the clinical samples of oropharyngeal squamous cell carcinoma and revealed that 13/24 cases (54%) were positive for phosphorylated p53. Importantly, the lymphocytes specific for the phosphorylated p53 peptide epitopes were observed in the head and neck squamous cell cancer (HNSCC) patients. These results reveal that a combination of phosphorylated p53 peptides and chemotherapy could be a novel immunologic approach to treat HNSCC patients.

Programmed death-ligand 1 and its soluble form are highly expressed in nasal natural killer/T-cell lymphoma: a potential rationale for immunotherapy

Nasal natural killer/T-cell lymphoma (NNKTL) is an aggressive neoplasm with poor therapeutic responses and prognosis. The programmed death-1/programmed death-ligand 1 (PD-1/PD-L1) pathway plays an important role in immune evasion of tumor cells through T-cell exhaustion. The aim of the present study was to examine the expression of PD-L1 and PD-1 molecules in NNKTL. We detected the expression of PD-L1 in biopsy samples from all of the NNKTL patients studied. PD-L1 was found on both malignant cells and tumor-infiltrating macrophages, while PD-1-positive mononuclear cells infiltrated the tumor tissues in 36% of patients. Most significantly, soluble PD-L1 (sPD-L1) was present in sera of NNKTL patients at higher levels as compared to healthy individuals and the levels of serum sPD-L1 in patients positively correlated with the expression of PD-L1 in lymphoma cells of tumor tissues. In addition, the high-sPD-L1 group of patients showed significantly worse prognosis than the low-sPD-L1 group. Furthermore, we confirmed that membrane and soluble PD-L1 was expressed on the surface and in the culture supernatant, respectively, of NNKTL cell lines. The expression of PD-L1 was observed in tumor tissues and sera from a murine xenograft model inoculated with an NNKTL cell line. Our results suggest that sPD-L1 could be a prognostic predictor for NNKTL and open up the possibility of immunotherapy of this lymphoma using PD-1/PD-L1 axis inhibitors.