The programmed cell death protein 1 (PD1) is one of the checkpoints that regulates the immune response. Ligation of PD1 with its ligands PDL1 and PDL2 results in transduction of negative signals to T-cells. PD1 expression is an important mechanism contributing to the exhausted effector T-cell phenotype. The expression of PD1 on effector T-cells and PDL1 on neoplastic cells enables tumor cells to evade anti-tumor immunity. Blockade of PD1 is an important immunotherapeutic strategy for cancers. Pembrolizumab (Keytruda) is a humanized monoclonal anti-PD1 antibody that has been extensively investigated in numerous malignancies. In melanoma refractory to targeted therapy, pembrolizumab induced overall response rates (ORRs) of 21-34%. It was superior to another immune checkpoint inhibitor ipilimumab (Yervoy) in stage III/IV unresectable melanoma. In refractory non-small cell lung cancer (NSCLC), pembrolizumab induced ORRs of 19-25%. Based on these results, pembrolizumab was approved by the USA FDA for the treatment of advanced melanoma and NSCLC. Tumor cell PDL1 expression may be a valid response predictor. Molecular analysis also showed that tumors with high gene mutation burdens, which might result in the formation of more tumor-related neo-antigens, had better responses to pembrolizumab. In malignancies including lymphomas and other solid tumors, preliminary data showed that ORRs of around 20-50 % could be achieved. Adverse events occurred in up to 60% of patients, but grade 3/4 toxicities were observed in <10% of cases. Immune-related adverse events including thyroid dysfunction, hepatitis and pneumonitis are more serious and may lead to cessation of treatment.

Natural killer (NK)/T-cell lymphomas failing L-asparaginse regimens have no known salvage and are almost invariably fatal. Seven male patients with NK/T-cell lymphoma (median age, 49 years; range, 31-68 years) for whom a median of 2 (range, 1-5) regimens (including l-asparaginase regimens and allogeneic hematopoietic stem-cell transplantation [HSCT] in 2 cases) failed were treated with the anti–programmed death 1 (PD1) antibody pembrolizumab. All patients responded, according to various clinical, radiologic (positron emission tomography), morphologic, and molecular (circulating Epstein-Barr virus [EBV] DNA) criteria. Two patients achieved complete response (CR) in all parameters. Three patients achieved clinical and radiologic CRs, with two having molecular remission (undetectable EBV DNA) but minimal EBV-encoded RNA-positive cells in lesions comprising predominantly CD3⁺CD4⁺ and CD3⁺CD8⁺ T cells (which ultimately disappeared, suggesting they represented pseudoprogression) and one having detectable EBV DNA despite morphologic CR. Two patients achieved partial response (PR). After a median of 7 (range, 2-13) cycles of pembrolizumab and a follow-up of a median of 6 (range, 2-10) months, all five CR patients were still in remission. The only adverse event was grade 2 skin graft-versus-host disease in one patient with previous allogeneic HSCT. Expression of the PD1 ligand was strong in 4 patients (3 achieving CR) and weak in 1 (achieving PR). PD1 blockade with pembrolizumab was a potent strategy for NK/T-cell lymphomas failing l-asparaginase regimens. Publisher9s Note: There is an Inside Blood Commentary on this article in this issue. Key Points NK/T-cell lymphomas failing L-asparaginse, generally fatal, showed a high CR rate to PD1 blockade with pembrolizumab. Comprehensive clinical, radiologic, pathologic, and molecular assessments showed different patterns of CRs and PRs.

Natural killer/T-cell lymphoma is rare and aggressive, with poor outcome. Optimal treatment remains unclear. A novel regimen dexamethasone, methotrexate, ifosfamide, l-asparaginase, and etoposide (SMILE) showed promise in phase 1/2 studies with restrictive recruitment criteria. To define the general applicability of SMILE, 43 newly diagnosed and 44 relapsed/refractory patients (nasal, N = 60, nonnasal, N = 21; disseminated, N = 6; male, N = 59; female, N = 28) at a median age of 51 years (23-83 years) were treated. Poor-risk factors included stage III/IV disease (56%), international prognostic index of 3 to 5 (43%), and Korean prognostic scores of 3 to 4 (41%). A median of 3 (0-6; total = 315) courses of SMILE were administered. Significant toxicities included grade 3/4 neutropenia (N = 57; 5 sepsis-related deaths); grade 3/4 thrombocytopenia (N = 36); and nephrotoxicity (N = 15; 1 acute renal failure and death). Interim analysis after 2 to 3 cycles showed complete remission rate of 56%, partial remission rate of 22%, giving an overall response rate of 78%. On treatment completion, the overall-response rate became 81% (complete remission = 66%, partial remission = 15%). Response rates were similar for newly diagnosed or relapsed/refractory patients. At a median follow-up of 31 months (1-84 months), the 5-year overall survival was 50% and 4-year disease-free-survival was 64%. Multivariate analysis showed that international prognostic index was the most significant factor impacting on outcome and survivals.

Extranodal natural killer (NK)/T-cell lymphoma is an aggressive malignancy of putative NK-cell origin, with a minority deriving from the T-cell lineage. Pathologically, the malignancy occurs in two forms, extranodal NK/T-cell lymphoma, nasal type; and aggressive NK-cell leukaemia. Lymphoma occur most commonly (80%) in the nose and upper aerodigestive tract, less commonly (20%) in non-nasal areas (skin, gastrointestinal tract, testis, salivary gland), and rarely as disseminated disease with a leukemic phase. Genetic analysis showed mutations of genes involved in the JAK/STAT pathway, RNA assembly, epigenetic regulation, and tumor suppression. In initial clinical evaluation, positron emission tomography computed tomography, and quantification of plasma EBV DNA are mandatory as they are useful for response monitoring and prognostication. In stage I/II diseases, combined chemotherapy and radiotherapy (sequentially or concurrently) is the best approach. Conventional anthracycline-containing regimens are ineffective and should be replaced by non-anthracycline-containing regimens, preferably including L-asparaginase. Radiotherapy alone is associated with high systemic relapse rates and should be avoided. In stage III/IV diseases, non-anthracycline-regimens-containing L-asparaginase are the standard. In relapsed/refractory cases, blockade of the programmed death protein 1 has recently shown promising results with high response rates. In the era of effective non-anthracycline-containing regimens, autologous haematopoietic stem cell transplantation (HSCT) has not been shown to be beneficial. However, allogeneic HSCT may be considered for high-risk or advanced-stage patients in remission or relapsed/refractory patients responding to salvage therapy. Prognostic models taking into account presentation, interim, and end-of-treatment parameters are useful in triaging patients to different treatment strategies.

Background: E-cadherin is an adhesion molecule involved in tumour invasion/metastasis. Silencing of E-cadherin by promoter CpG methylation has been shown in both familial and sporadic gastric cancers. Helicobacter pylori is a class I carcinogen in gastric cancer. Aims: This study was undertaken to investigate the association between methylation of E-cadherin and H pylori in gastric mucosa from dyspeptic patients, and in intestinal metaplasia and primary and metastatic adenocarcinoma from surgical specimens of patients with gastric cancer. Methods: E-cadherin methylation was studied using methylation specific polymerase chain reaction in microdissected tissue from biopsies or surgical resection specimens. E-cadherin expression was studied by immunohistochemistry. Results: E-cadherin methylation was present in 31% (11/35) of gastric mucosae from dyspeptic patients, and was associated with H pylori infection (p=0.002), but was independent of the age of the patient or presence or absence of gastritis. E-cadherin methylation was present in 0% (0/8) of normal mucosa, 57% (12/21) of intestinal metaplasias, and 58% (15/26) of primary and 65% (21/32) of metastatic cancers. E-cadherin methylation status was concordant in 92% (11/12) of intestinal metaplasias and primary cancers, and in 85% (17/20) of primary and metastatic cancers from the same resected specimen. E-cadherin methylation in gastric cancer was associated with depth of tumour invasion (p=0.02) and regional nodal metastasis (p=0.05). Conclusion: E-cadherin methylation is an early event in gastric carcinogenesis, and is initiated by H pylori infection.