BackgroundRecent impressive advances in cancer immunotherapy have been largely derived from cellular immunity. The role of humoral immunity in carcinogenesis has been less understood. Based on our previous observations we hypothesize that an immunoglobulin subtype IgG4 plays an essential role in cancer immune evasion.MethodsThe distribution, abundance, actions, properties and possible mechanisms of IgG4 were investigated with human cancer samples and animal tumor models with an extensive array of techniques both in vitro and in vivo.ResultsIn a cohort of patients with esophageal cancer we found that IgG4-containing B lymphocytes and IgG4 concentration were significantly increased in cancer tissue and IgG4 concentrations increased in serum of patients with cancer. Both were positively related to increased cancer malignancy and poor prognoses, that is, more IgG4 appeared to associate with more aggressive cancer growth. We further found that IgG4, regardless of its antigen specificity, inhibited the classic immune reactions of antibody-dependent cell-mediated cytotoxicity, antibody-dependent cellular phagocytosis and complement-dependent cytotoxicity against cancer cells in vitro, and these effects were obtained through its Fc fragment reacting to the Fc fragments of cancer-specific IgG1 that has been bound to cancer antigens. We also found that IgG4 competed with IgG1 in reacting to Fc receptors of immune effector cells. Therefore, locally increased IgG4 in cancer microenvironment should inhibit antibody-mediated anticancer responses and help cancer to evade local immune attack and indirectly promote cancer growth. This hypothesis was verified in three different immune potent mouse models. We found that local application of IgG4 significantly accelerated growth of inoculated breast and colorectal cancers and carcinogen-induced skin papilloma. We also tested the antibody drug for cancer immunotherapy nivolumab, which was IgG4 in nature with a stabilizing S228P mutation, and found that it significantly promoted cancer growth in mice. This may provide an explanation to the newly appeared hyperprogressive disease sometimes associated with cancer immunotherapy.ConclusionThere appears to be a previously unrecognized immune evasion mechanism with IgG4 playing an essential role in cancer microenvironment with implications in cancer diagnosis and immunotherapy.

Correlation between microRNA (miRNA)-206 and miRNA-145 expression and prognosis in breast cancer was investigated. Breast cancer specimens and paracancerous tissues of 372 breast cancer patients who underwent surgical resection in the First Affiliated Hospital of Shantou University Medical College from September 2010 to September 2014 were included. qRT-PCR was used to detect the expression of miR-206 and miR-145 in breast cancer and paracancerous tissues, and patients were divided into high and low expression groups according to the median expression level to plot survival curve. Expression levels of miR-145 and miR-206 in breast cancer tissues were 2.24±1.23 and 0.76±0.24, respectively. Expression level of miR-145 was significantly lower, while expression level of miR-206 was significantly higher in tumor tissues than in paracancerous tissues (p<0.05). The 3-year survival rates of miR-145 low expression group and miR-206 high expression group were also lower than that of miR-145 high expression group and miR-206 low expression group, respectively (p<0.05). Expression of miR-206 is upregulated and expression of miR-145 is downregulated in breast cancer, which may have an impact on the prognosis of patients. miR-206 and miR-145 may serve as important indicators to predict prognosis of patients with breast cancer in the future.

To evaluate the occurrence, abundance, distribution, nature and clinical significance of multinucleated giant cell (MGC) in esophageal cancer. Materials and methods: MGCs were examined with conventional pathology, immunohistochemistry and immunofluorescence in 107 esophageal cancer tissues. The findings were correlated to pathological diagnosis and clinical behavior of the cancers. Results: MGCs were identified in 31.7% (34/107) of the cases. MGCs were positive for CD11c, CD11b, CD32, CD16, HLA-DR and MMP9, and negative for CD163, CD206 and CD64 giving a molecular profile of proinflammatory M1 but not immunosuppressive M2. MGCs were significantly related to decreased lymph node metastasis (p = 0.011), low pTNM stage (p = 0.044), favorable survival (p = 0.04), squamous cell cancer type rather than other histopathological subtypes (p = 0.020) and associated to better differentiation (p = 0.063). Conclusions: MGCs belong to M1 macrophage and perform phagocytosis and scavenging of cancer cells that would benefit patients' survival and could serve as a prognostic marker.

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Although DNA vaccines have shown a good antitumor effect in animal models, they are often not effective in clinical trials. This requires researchers to find an effective way to significantly improve the immunogenicity of vaccines. Here, we developed a new DNA vaccine based on MAGE-A3, which has been suggested as a potential target for lung cancer therapy. We enhanced the potency of this DNA vaccine by overcoming tumour-induced immunosuppressive environment through blockade of the PD-1/PD-L pathway using a soluble PD-1 (sPD1). A series of DNA plasmids encoding MAGE-A3, the extracellular domain of murine PD-1 (sPD1) and their conjugates were constructed and injected into female mice intramuscularly (i.m.) followed by an electric pulse. The humoral and cellular immune responses after immunization were evaluated by enzyme-linked immunosorbent assay (ELISA) and enzyme-linked immunospot assay (ELISPOT), respectively. To evaluate the therapeutic efficacy of the plasmids, a mouse model with a MAGE-A3-expressing tumour was designed. Mice vaccinated with the fusion expression plasmid generated the strongest MAGE-A3-specific immune responses. Furthermore, these vaccinations inhibited the growth of MAGE-A3-expressing tumours and prolonged mouse survival. These findings suggest that the combination of DNA vaccines with PD-1 pathway inhibitors may be a promising approach in clinical trials. This approach may be viable for vaccines targeting cancer, as anti-tumour vaccines have demonstrated clinical benefit but PD-1 pathway inhibitors alone have demonstrated poor efficacy so far.