Radiotherapy-induced anti-tumor immunity contributes to the therapeutic efficacy of irradiation and can be augmented by CTLA-4 blockade in a mouse model.

PURPOSE: There is growing evidence that tumor-specific immune responses play an important role in anti-cancer therapy, including radiotherapy. Using mouse tumor models we demonstrate that irradiation-induced anti-tumor immunity is essential for the therapeutic efficacy of irradiation and can be augmented by modulation of cytotoxic T lymphocyte (CTL) activity. METHODS AND MATERIALS: C57BL/6 mice, syngeneic EL4 lymphoma cells, and Lewis lung carcinoma (LL/C) cells were used. Cells were injected into the right femurs of mice. Ten days after inoculation, tumors were treated with 30 Gy of local X-ray irradiation and their growth was subsequently measured. The effect of irradiation on tumor growth delay (TGD) was defined as the time (in days) for tumors to grow to 500 mm3 in the treated group minus that of the untreated group. Cytokine production and serum antibodies were measured by ELISA and flow cytometry. RESULTS: In the EL4 tumor model, tumors were locally controlled by X-ray irradiation and re-introduced EL4 cells were completely rejected. Mouse EL4-specific systemic immunity was confirmed by splenocyte cytokine production and detection of tumor-specific IgG1 antibodies. In the LL/C tumor model, X-ray irradiation also significantly delayed tumor growth (TGD: 15.4 days) and prolonged median survival time (MST) to 59 days (versus 28 days in the non-irradiated group). CD8(+) cell depletion using an anti-CD8 antibody significantly decreased the therapeutic efficacy of irradiation (TGD, 8.7 days; MST, 49 days). Next, we examined whether T cell modulation affected the efficacy of radiotherapy. An anti-CTLA-4 antibody significantly increased the anti-tumor activity of radiotherapy (TGD was prolonged from 13.1 to 19.5 days), while anti-FR4 and anti-GITR antibodies did not affect efficacy. CONCLUSIONS: Our results indicate that tumor-specific immune responses play an important role in the therapeutic efficacy of irradiation. Immunomodulation, including CTLA-4 blockade, may be a promising treatment in combination with radiotherapy.

The MAPK pathway is a predominant regulator of HLA-A expression in esophageal and gastric cancer.

Downregulation of HLA class I expression may contribute to a poor prognosis in cancer patients. There is limited information about epigenetic and oncogenic regulation of HLA class I, and multiple mechanisms may be involved. In the current study, we examined the relationship between the HER2-signaling pathway (MAPK and PI3K-Akt) and the expression of HLA class I and Ag-processing machinery (APM) components. A panel of gastric and esophageal cancer cell lines was treated with wortmannin as an Akt-signal inhibitor; the MAPK signal inhibitor PD98059; lapatinib, which inhibits both the epidermal growth factor receptor and HER2 tyrosine kinase; or siRNA for MAPK. The levels of HER2-signaling molecules, APM components, and HLA class I were evaluated by Western blot, quantitative PCR, and flow cytometry. Resected gastric tumor tissues (n = 102) were analyzed for p-Erk and HLA class I expression by immunohistochemistry. As a result, inhibition of the MAPK pathway induced upregulation of HLA-A02 and HLA-A24 expression in parallel with an increase in APM components and enhanced target sensitivity to tumor Ag-specific CTL lysis. HLA-A expression was predominantly regulated by the MAPK pathway, but it was also influenced, in part, by the Akt pathway. There was a strong inverse correlation between p-Erk expression and HLA class I expression in clinical tumor samples. In conclusion, HLA-A expression is predominantly regulated by the MAPK pathway in gastric and esophageal cancer.

Lapatinib acts on gastric cancer through both antiproliferative function and augmentation of trastuzumab-mediated antibody-dependent cellular cytotoxicity.

BACKGROUND: Trastuzumab has been recently approved for clinical use to treat HER2-expressing advanced gastric cancer, and anti-HER2-targeting therapy has become a promising option for gastric cancer. Lapatinib is a dual tyrosine kinase inhibitor targeting EGFR and HER2. The aim of the present study was to explore the utility of lapatinib for gastric cancer, with a particular focus on trastuzumab-mediated antibody-dependent cellular cytotoxicity (ADCC). METHODS: Nine gastric cancer cell lines were evaluated for the effects of lapatinib on the cell-surface accumulation of HER2 and analyzed for their additional effects on trastuzumab-mediated ADCC. Also, HER2 signaling with Western blot, proliferative function with the MTT assay, and apoptosis-inducing activity with 7ADD/Annexin-V were investigated when a panel of gastric cancer cell lines was treated with lapatinib. RESULTS: Lapatinib inhibited HER2 signaling and cell proliferation in the panel of gastric cancer cell lines. Lapatinib also induced the accumulation of HER2 on the cell surface, resulting in the enhancement of trastuzumab-mediated ADCC of gastric cancer. CONCLUSIONS: Lapatinib exhibits inhibitory activity in gastric cancer cells, and the combination of lapatinib with trastuzumab may be a promising treatment strategy for gastric cancer patients.

Expression of MHC Class I on breast cancer cells correlates inversely with HER2 expression.

HER2 is a promising target for immunotherapeutic interventions with T cell-based approaches since it is amplified and overexpressed in 20-30% of breast cancers. However, several previous studies including ours showed that HER2-overexpressing tumors may escape cytotoxic T lymphocyte-mediated lysis by downregulating MHC Class I and components of the antigen-processing machinery. The aims of the present study were to analyze the relationship between HER2 and MHC Class I expression and to elucidate the mechanisms underlying MHC Class I downregulation in breast cancer. We explored expression of HER2, MHC Class I, PTEN, Ki67, estrogen and progesterone expression in 70 breast cancer patients by immunohistochemistry (IHC) and analyzed their correlation. We also explored the components of the signal transduction pathway that are involved in the regulation of MHC Class I expression using small-interfering RNAs targeting HER2 as well as an inhibitor of HER2 signaling. HER2 expression in breast cancers correlated inversely with MHC Class I expression analyzed by IHC. HER2 depletion by small-interfering RNAs resulted in MHC Class I upregulation. Moreover, MHC Class I expression on breast cancer cell lines was upregulated by PD98059, an inhibitor of mitogen-associated protein kinases, in a dose-dependent manner. Thus, agents that target the MAPK signaling pathway may increase MHC Class I expression in breast cancer cells.

[The effect of immune-based therapy with cytotoxic T lymphocyte and molecular targeting therapy for HER2 in esophageal squamous cell carcinoma].

Although esophageal squamous cell carcinoma (ESCC) patients have recently been treated with the combined modality therapy, the prognosis remains poor. For the development of new strategies in ESCC, we examined possibilities of the immune -based therapy with cytotoxic T lymphocyte (CTL) and the molecular targeting therapy for HER2 against ESCC in this study. At first, we assessed HER2 and MHC class I expression by immunohistochemistry in ESCC patients and analyzed the correlation between them. Subsequently, the effect of molecular targeting therapy for HER2 was evaluated in a panel of ESCC cell lines. According to these results, we suggested that HER2 over-expressing ESCC patients (11.8%) are good candidates for the molecular targeting therapy for HER2 and HER2 negative/low-expressing ESCC patients (88.2%) for the immune-based therapy with CTL. Furthermore, the combination therapy of Herceptin and lapatinib is a new promising strategy for HER2 positive ESCC patients (29.4%).

Lapatinib enhances herceptin-mediated antibody-dependent cellular cytotoxicity by up-regulation of cell surface HER2 expression.

BACKGROUND: Although it was previously reported that lapatinib combined with Herceptin improved the progression-free survival rate compared with lapatinib alone for patients with Herceptin-refractory HER2-positive metastatic breast cancer, the mechanism is purported to be an antiproliferative effect relating to the synergism of these two agents. MATERIALS AND METHODS: We evaluated how lapatinib interacts with Herceptin in HER2-positive breast cancer, with a particular focus on Herceptin-mediated antibody-dependent cellular cytotoxicity (ADCC). RESULTS: In an in vitro assay, lapatinib induced HER2 expression at the cell surface of HER2-positive breast cancer cell lines, leading to the enhancement of Herceptin-mediated ADCC. Furthermore, we present a case report in which a second Herceptin treatment following lapatinib resulted in the marked shrinkage of multiple metastatic tumors in HER2-positive breast cancer. CONCLUSION: Lapatinib may have the potential to convert Herceptin-refractory to Herceptin-sensitive tumors in HER2-positive breast cancer by up-regulation of the cell surface expression of HER2.

Immunonutritional diet modulates natural killer cell activation and Th17 cell distribution in patients with gastric and esophageal cancer.

OBJECTIVE: Although randomized clinical trials have shown that immunonutrition results in the improvement of postoperative complications, the detailed mechanisms of its immunomodulation are still unclear. In the present study, we investigated if such immunonutrition could affect T-cell and natural killer (NK) cell functions, with particular focus on type 17 helper T (Th17) cells and NK cell-activating markers, in patients with esophageal and gastric cancer and in healthy volunteers. METHODS: Patients (n = 22) and healthy volunteers (n = 10) were orally administered an immunonutritional diet (Impact, 750 mL/d) in addition to a conventional diet for 5 d. The expression of NK cell-activation markers (NKG2D, CD16, CD107a, NKp30, NKp44, and NKp46), frequency of CD56(dim) NK, Th17, and regulatory T cells, and trastuzumab-mediated antibody-dependent cell-mediated cytotoxicity were analyzed before and after immunonutrition. RESULTS: Immunonutrition significantly enhanced antibody-dependent cell-mediated cytotoxic activity as an NK cell function, paralleling the upregulated expression of NKG2D and CD16 and increased frequency of CD56(dim) NK cells. Furthermore, the immunonutrition significantly increased the frequency of Th17 cells. CONCLUSION: Immunonutrition modulates NK and T-cell-mediated immunity.

Lapatinib inhibits receptor phosphorylation and cell growth and enhances antibody-dependent cellular cytotoxicity of EGFR- and HER2-overexpressing esophageal cancer cell lines.

Lapatinib is a dual tyrosine kinase inhibitor of the EGFR and HER2 tyrosine kinase domains. EGFR is expressed in 33.3% and HER2 in 30.3% of esophageal squamous cell carcinomas (ESCCs). To explore the potential utility of Lapatinib for therapy of ESCC patients, we evaluated the effect of Lapatinib on a panel of ESCC cell lines. EGFR and HER2 expression by the cell lines was established, and the effects of Lapatinib on inhibition of the phosphorylation of HER2, antiproliferative effect, apoptosis-inducing activity and accumulation of HER2 and EGFR on cell surface were evaluated. Additionally, the combined effect of Lapatinib together with Herceptin or Cetuximab on cell-mediated cytotoxicity was evaluated. Lapatinib inhibited HER2 phosphorylation in HER2-overexpressing, HER2 gene amplification positive ESCC cell line. Lapatinib also inhibited cell proliferation, induced apoptosis and caused the surface accumulation of HER2 and EGFR in ESCC cell lines. Addition of Lapatinib increased Herceptin-mediated antibody-dependent cell-mediated cytotoxicity by 15-25% with three ESCC target cell lines. Similarly, Cetuximab-mediated antibody-dependent cell-mediated cytotoxicity also increased by 15-30% in two ESCC cell lines on addition of Lapatinib. Cumulatively, the data indicate that Lapatinib has activity in EGFR- and/or HER2-expressing ESCC cells, and the combination therapy of Lapatinib and Cetuximab/Herceptin is a promising strategy in ESCC.