MK-6, a novel not-α IL-2, elicits a potent antitumor activity by improving the effector to regulatory T cell balance.

IL-2 is a pleiotropic cytokine that regulates immune cell homeostasis. Its immunomodulatory function has been used clinically as an active immunotherapy agent for metastatic cancers. However, severe adverse effects, including the vascular leak syndrome and the preferential stimulation of anti-immunogenic Treg rather than effector T cells, have been obstacles. We newly designed a mutein IL-2, Mutakine-6 (MK-6), with reduced IL-2Rα-binding capability. MK-6 induced comparable cell growth potential toward IL-2Rßγ-positive T cells but was far less efficient in in vitro Treg proliferation and STAT5 activation. Unlike IL-2, in vivo administration of MK-6 produced minimal adverse effects. Using CT26 and B16F10-syngeneic tumor models, we found MK-6 was highly efficacious on tumor regression. Serum albumin conjugation to MK-6 prolonged in vivo half-life and accumulated in CT26 tumors, showing enhanced antitumor effect. Tumor-infiltrating leukocytes analysis revealed that albumin-fused MK-6 increased the ratio of effector CD8+ T cells to CD4+ Treg cells. These results demonstrated that MK-6 is an efficient immunomodulator potentially used for improved immunotherapy with decreased adverse effects and attenuated Treg stimulation.

CD271 regulates the proliferation and motility of hypopharyngeal cancer cells.

CD271 (p75 neurotrophin receptor) plays both positive and negative roles in cancer development, depending on the cell type. We previously reported that CD271 is a marker for tumor initiation and is correlated with a poor prognosis in human hypopharyngeal cancer (HPC). To clarify the role of CD271 in HPC, we established HPC cell lines and knocked down the CD271 expression using siRNA. We found that CD271-knockdown completely suppressed the cells' tumor-forming capability both in vivo and in vitro. CD271-knockdown also induced cell-cycle arrest in G0 and suppressed ERK phosphorylation. While treatment with an ERK inhibitor only partially inhibited cell growth, CDKN1C, which is required for maintenance of quiescence, was strongly upregulated in CD271-depleted HPC cells, and the double knockdown of CD271 and CDKN1C partially rescued the cells from G0 arrest. In addition, either CD271 depletion or the inhibition of CD271-RhoA signaling by TAT-Pep5 diminished the in vitro migration capability of the HPC cells. Collectively, CD271 initiates tumor formation by increasing the cell proliferation capacity through CDKN1C suppression and ERK-signaling activation, and by accelerating the migration signaling pathway in HPC.

Synergistic cytotoxicity of afatinib and cetuximab against EGFR T790M involves Rab11-dependent EGFR recycling.

EGFR is an important therapeutic target for non-small cell lung cancers (NSCLCs). Tyrosine kinase inhibitors (TKIs), such as gefitinib and erlotinib, are effective in cases with EGFR-activating mutations. However, most such cases become resistant through a secondary EGFR mutation, T790M. While the second-generation TKI afatinib has a higher affinity for double-mutant EGFRs, better efficacy is needed. Combining afatinib with the anti-EGFR monoclonal antibody cetuximab improves clinical outcomes, but the mechanism is unclear. Here we examined this effect using erythroleukemic K562 cells. The activating EGFR mutation L858R is sensitive to first-generation TKIs, and adding T790M confers resistance to these drugs. This double-mutant EGFR was moderately sensitive to afatinib, but responded weakly to cetuximab. Combined afatinib and cetuximab synergistically increased their cytotoxicity for K562 cells expressing the double-mutant EGFR. Apoptosis in these cells followed induction of the pro-apoptotic protein BIM. Unexpectedly, afatinib caused redistribution of EGFR to the cell surface through Rab11a-dependent recycling. Cetuximab reduced cell-surface EGFR, and total EGFR decreased synergistically when cetuximab was combined with afatinib. Our results suggest that the synergistic effect exerted by afatinib and cetuximab on NSCLCs is associated with BIM induction and alterations in EGFR status.

Life-prolonging effect of immunocell BAK (BRM-activated killer) therapy for advanced solid cancer patients: prognostic significance of serum immunosuppressive acidic protein levels.

We devised an innovative type of immunocell therapy called BRM (biological response modifier)-activated killer (BAK) therapy, which utilizes most of non-MHC (major histocompatibility complex) restricted lymphocytes, CD56+ cells including gammadelta T cells and NK cells. Peripheral blood lymphocytes were selected by immobilizing them with anti-CD3 monoclonal antibody, cultured for 2 weeks with serum-free medium containing IL-2, and then were reactivated by 1,000 U/ml of IFN-alpha for 15 min. The patients were infused with about 6x10(9) BAK cells by intravenous drip infusion at 1-month intervals. All advanced solid cancer patients who had received chemotherapy but for whom it was not effective or have refused chemotherapy were included in the present study. A good marker of impairment of host immune response by chemotherapy is an immunosuppressive acidic protein (IAP) level in serum above 580 microg/ml; survival rates were compared with the high (> 580 microg/ml) and the low (< or = 580 microg/ml) serum IAP groups. We enrolled in this study 23 immunosuppressed patients whose IAP levels in serum were over 580 microg/ml, and 42 immunoreactive solid cancer outpatients whose IAP level in serum were under 580 degreesg/ml and whose performance statuses were over 80% on the Karnofsky scale. After giving informed consent, patients were treated with BAK therapy on an outpatient basis at our hospital. The ethical review board of the Miyagi Cancer Center approved this pilot study. Treated with BAK therapy, the mean survival of immunosuppressed patients was 4.6 months. On the other hand, survival for one of immunoreactive advanced postoperative patients (stage IV) and inoperable lung cancer patients (stage IIIb) was 24.7 months. The difference in survival between the 2 groups was significant (P < 0.01). This shows that BAK therapy is not indicated for an advanced cancer patient whose serum IAP is over 580 microg/ml, perhaps due to extensive chemotherapy. Overall response to BAK therapy was complete response (CR) in 5 cases, partial response (PR) in 1 case, and prolonged no change (NC) in 26 cases, with an effectiveness rate at 76.2% in 42 advanced stage IIIb and IV cancer patients. BAK therapy has a life-prolonging effect without any adverse effects and maintains satisfactory quality of life (QOL) for advanced cancer patients.