Amplifying cancer vaccine responses by modifying pathogenic gene programs in tumor cells

Direct and indirect effects of IFN-α2b in malignancy treatment: not only an archer but also an arrow

Interferon-α2b (IFN-α2b) is a highly active cytokine that belongs to the interferon-α (IFN-α) family. IFN-α2b has beneficial antiviral, antitumour, antiparasitic and immunomodulatory activities. Direct and indirect antiproliferative effects of IFN-α2b have been found to occur via multiple pathways, mainly the JAK-STAT pathway, in certain cancers. This article reviews mechanistic studies and clinical trials on IFN-α2b. Potential regulators of the function of IFN-α2b were also reviewed, which could be utilized to relieve the poor response to IFN-α2b. IFN-α2b can function not only by enhancing the systematic immune response but also by directly killing tumour cells. Different parts of JAK-STAT pathway activated by IFN-α2b, such as interferon alpha and beta receptors (IFNARs), Janus kinases (JAKs) and IFN‐stimulated gene factor 3 (ISGF3), might serve as potential target for enhancing the pharmacological action of IFN-α2b. Despite some issues that remain to be solved, based on current evidence, IFN-α2b can inhibit disease progression and improve the survival of patients with certain types of malignant tumours. More efforts should be made to address potential adverse effects and complications.

Knowledge database assisted gene marker selection for chronic lymphocytic leukemia

Objective

To investigate whether previously curated chronic lymphocytic leukemia (CLL) risk genes could be leveraged in gene marker selection for the diagnosis and prediction of CLL.

Methods

A CLL genetic database (CLL_042017) was developed through a comprehensive CLL-gene relation data analysis, in which 753 CLL target genes were curated. Expression values for these genes were used for case-control classification of four CLL datasets, with a sparse representation-based variable selection (SRVS) approach employed for feature (gene) selection. Results were compared with outcomes obtained by using analysis of variance (ANOVA)-based gene selection approaches.

Results

For each of the four datasets, SRVS selected a subset of genes from the 753 CLL target genes, resulting in significantly higher classification accuracy, compared with randomly selected genes (100%, 100%, 93.94%, 89.39%). The SRVS method outperformed ANOVA in terms of classification accuracy.

Conclusion

Gene markers selected from the 753 CLL genes could enable significantly greater accuracy in the prediction of CLL. SRVS provides an effective method for gene marker selection.

Functional variants of IL4 and IL6 genes and risk of tobacco-related oral carcinoma in high-risk Asian Indians

BACKGROUND

Tobacco-related oral squamous cell carcinoma (OSCC) is one of the most common cancers involving Indian males. We assessed the association of IL4 promoter -589 T>C, -33 T>C, and IL6-174 G>C functional genetic polymorphisms with tobacco-related OSCC in Asian Indians.

PATIENTS AND METHODS

The IL4 and IL6 promoter polymorphisms were assessed in 140 patients with OSCC and 120 normal subjects by PCR-RFLP technique, and significance of the data was determined using chi-square test.

RESULTS

The frequency of TC, CC genotype, and C allele at IL4 promoter sites -589 and -33 were higher in patients when compared with controls. Consequently, TC/CC genotypes and C allele at both sites appeared as susceptible. However, IL6-174 G>C single-nucleotide polymorphisms (SNP) appeared to be protective in patients with OSCC. Of eight haplotypes, five were associated with two- to seven-fold increased risk of tobacco-related OSCC. These SNPs further showed heterogeneity among different ethnic population, but their distribution in Asian Indians stand closer to other Asian populations.

CONCLUSIONS

In this study, IL4-589 CC, -33 CC genotype, and *C allele at both sites appeared to be susceptible, while IL6-174 CC genotype and *C allele appeared to be protective in patients with OSCC; hence, these SNPs may be a potential prognostic markers for tobacco-related OSCC in Asian Indians.

CTLA4 blockade induces frequent tumor infiltration by activated lymphocytes regardless of clinical responses in humans

BACKGROUND

CTLA4 blocking monoclonal antibodies provide durable clinical benefit in a subset of patients with advanced melanoma mediated by intratumoral lymphocytic infiltrates. A key question is defining whether the intratumoral infiltration (ITI) is a differentiating factor between patients with and without tumor responses.

METHODS

Paired baseline and postdosing tumor biopsy specimens were prospectively collected from 19 patients with metastatic melanoma, including 3 patients with an objective tumor response, receiving the anti-CTLA4 antibody tremelimumab within a clinical trial with primary endpoint of quantitating CD8(+) cytotoxic T-lymphocyte (CTL) infiltration in tumors. Samples were analyzed for cell density by automated imaging capture and further characterized for functional lymphocyte properties by assessing the cell activation markers HLA-DR and CD45RO, the cell proliferation marker Ki67, and the regulatory T-cell marker FOXP3.

RESULTS

There was a highly significant increase in ITI by CD8(+) cells in biopsy samples taken after tremelimumab treatment. This included increases between 1-fold and 100-fold changes in 14 of 18 evaluable cases regardless of clinical tumor response or progression. There was no difference between the absolute number, location, or cell density of infiltrating cells between clinical responders and patients with nonresponding lesions that showed acquired intratumoral infiltrates. There were similar levels of expression of T-cell activation markers (CD45RO, HLA-DR) in both groups and no difference in markers for cell replication (Ki67) or the suppressor cell marker FOXP3.

CONCLUSION

CTLA4 blockade induces frequent increases in ITI by T cells despite which only a minority of patients have objective tumor responses.

Aberrant interferon-signaling is associated with aggressive chronic lymphocytic leukemia

The type I interferons (IFNs) normally suppress tumor growth by phosphorylating and activating the signal transducer and activator of transcription 1 (STAT1), but also briefly activate STAT3, which promotes cell growth. In chronic lymphocytic leukemia (CLL) cells, the duration of IFN-mediated STAT3 phosphorylation was found to exhibit significant interpatient variability and was prolonged in cells with high risk features, such as 11q- and 17p-deletions involving ataxia telangiectasia mutated (ATM) and p53. This aberrant signaling pattern was associated with a paradoxical increase in cell size and number in response to IFN and similar alterations in IFN-signaling and responses were seen in cell lines that developed in the absence of p53 or ATM. However, direct inhibition of p53 or ATM failed to cause these changes, and CLL cells with aggressive clinical features were found to also express high levels of reactive oxygen species (ROS), which decrease tyrosine phosphatase activity. Prolonged IFN-mediated STAT3 phosphorylation and lowered phosphatase activity could be reversed by antioxidants. These findings suggest that increased ROS levels may corrupt IFN-signaling processes in aggressive CLL cells, causing IFN to be used as a growth factor rather than a tumor suppressor. Antioxidants or STAT3 kinase inhibitors might improve the outcome of IFN therapy in CLL by restoring normal signaling.

How do tumors actively escape from host immunosurveillance?

The immunological background for the process of tumor growth is still obscure. However, our understanding of what happens could have important consequences, namely in the context of cancer immunotherapy. A tumor is able to grow in the host environment either because it is recognizable as normal tissue and tolerated by host immune cells, or because it can "escape" from host immunosurveillance. According to the second option the mechanisms of tumor recognition and consequent destruction are actively disturbed by such processes as: change of tumor immunogenicity, production of tumor-derived regulatory molecules, and interaction of cancer cells with tumor-infiltrating immune cells. The results of studies devoted to the problem of immunoregulation in the tumor environment seem to support the "escape" hypothesis.

OPTIM trial: a Phase III trial of an oncolytic herpes virus encoding GM-CSF for unresectable stage III or IV melanoma

There are few effective treatment options available for patients with advanced melanoma. An oncolytic herpes simplex virus type 1 encoding granulocyte macrophage colony-stimulating factor (GM-CSF; Oncovex(GM-CSF)) for direct injection into accessible melanoma lesions resulted in a 28% objective response rate in a Phase II clinical trial. Responding patients demonstrated regression of both injected and noninjected lesions highlighting the dual mechanism of action of Oncovex(GM-CSF) that includes both a direct oncolytic effect in injected tumors and a secondary immune-mediated anti-tumor effect on noninjected tumors. Based on these preliminary results a prospective, randomized Phase III clinical trial in patients with unresectable Stage IIIb or c and Stage IV melanoma has been initiated. The rationale, study design, end points and future development of the Oncovex(GM-CSF) Pivotal Trial in Melanoma (OPTIM) trial are discussed in this article.

Immunotherapy for melanoma: current status and perspectives

Immunotherapy is an important modality in the therapy of patients with malignant melanoma. As our knowledge about this disease continues to expand, so does the immunotherapeutic armamentarium. Nevertheless, successful preclinical models do not always translate into clinically meaningful results. The authors give a comprehensive analysis of most recent advances in the immune anti-melanoma therapy, including interleukins, interferons, other cytokines, adoptive immunotherapy, biochemotherapy, as well as the use of different vaccines. We also present the fundamental concepts behind various immune enhancement strategies, passive immunotherapy, as well as the use of immune adjuvants. This review brings into discussion the results of newer and older clinical trials, as well as potential limitations and drawbacks seen with the utilization of various immune therapies in malignant melanoma. Development of novel therapeutic approaches, along with optimization of existing therapies, continues to hold a great promise in the field of melanoma therapy research. Use of anti-CTLA4 and anti-PD1 antibodies, realization of the importance of co-stimulatory signals, which translated into the use of agonist CD40 monoclonal antibodies, as well as activation of innate immunity through enhanced expression of co-stimulatory molecules on the surface of dendritic cells by TLR agonists are only a few items on the list of recent advances in the treatment of melanoma. The need to engineer better immune interactions and to boost positive feedback loops appear crucial for the future of melanoma therapy, which ultimately resides in our understanding of the complexity of immune responses in this disease.

Does our current understanding of immune tolerance, autoimmunity, and immunosuppressive mechanisms facilitate the design of efficient cancer vaccines?

The therapeutic use of the immune system to attack cancer cells has been a longstanding vision among tumour immunologists. However, most human tumours are poorly immunogenic and are able to invade the host immune system. Although these obstacles are clearly critical to cancer vaccine development, the induction of a strong anti-tumour immune response may rely on the activation of high affinity T cells through a molecular mimicry mechanism which involves cross-reactive recognition of foreign antigens mimicking the structure of tumour proteins. Taking into account the disparity in HLA molecules needed to present shared antigens; in late 1990s Stauss et al. described the possibility of generating allorestricted high affinity cytotoxic T cells against synthetic self-peptides bound to non-self-MHC molecules. In addition to the strategies indicated above, the inhibition of the immunosuppressive mechanisms associated with tumour invasion of the immune system using RNA interference also offers a new approach to vaccine design. This review highlights the problem of immune tolerance, the induction of autoreactive T cells, and describes strategies to enhance tumour immunity.

Prolonging microtubule dysruption enhances the immunogenicity of chronic lymphocytic leukaemia cells

Cytotoxic chemotherapies do not usually mediate the expression of an immunogenic gene programme in tumours, despite activating many of the signalling pathways employed by highly immunogenic cells. Concomitant use of agents that modulate and complement stress-signalling pathways activated by chemotherapeutic agents may then enhance the immunogenicity of cancer cells, increase their susceptibility to T cell-mediated controls and lead to higher clinical remission rates. Consistent with this hypothesis, the microtubule inhibitor, vincristine, caused chronic lymphocytic leukaemia (CLL) cells to die rapidly, without increasing their immunogenicity. Protein kinase C (PKC) agonists (such as bryostatin) delayed the death of vincristine-treated CLL cells and made them highly immunogenic, with increased stimulatory abilities in mixed lymphocyte responses, production of proinflammatory cytokines, expression of co-stimulatory molecules and activation of c-Jun N-terminal kinase (JNK), p38 and nuclear factor kappa B (NF-kappaB) signalling pathways. This phenotype was similar to the result of activating CLL cells through Toll-like receptors (TLRs), which communicate 'danger' signals from infectious pathogens. Use of PKC agonists and microtubule inhibitors to mimic TLR-signalling, and increase the immunogenicity of CLL cells, has implications for the design of chemo-immunotherapeutic strategies.

Toll-like receptor-7 tolerizes malignant B cells and enhances killing by cytotoxic agents

Chronic activation through Toll-like receptors (TLR) occurs in a number of pathologic settings, but has not been studied to the same extent as primary activation. TLR7, expressed by B cells and some dendritic cells, recognizes molecular patterns associated with viruses that can be mimicked by synthetic imidazoquinolines. In response to primary stimulation with the imidazoquinoline, S28690, human mononuclear cells produced tumor necrosis factor-alpha, but were unable to do so upon restimulation with S28690. This state of "tolerization" lasted at least 5 days. Using chronic lymphocytic leukemia B cells as a model to facilitate biochemical analysis, the tolerized state was found to be associated with altered receptor components, including down-regulated expression of TLR7 mRNA and decreased levels of interleukin-1 receptor-associated kinase 1. Tolerization was characterized by a transcriptionally regulated block in stress-activated protein kinase and nuclear factor kappaB activation, with relatively preserved activation of extracellular signal-regulated kinase (ERK). Tolerized chronic lymphocytic leukemia cells were found to be more sensitive to cytotoxic chemotherapeutic agents, in part through altered stress-activated protein kinase signaling pathways. This property of the TLR7-tolerized state may potentially be exploited in the treatment of B cell cancers.

Toll-like receptor agonists in the treatment of chronic lymphocytic leukemia

Advances in our understanding of the Toll-like receptors (TLRs) have led to the identification of several agonists that are suitable for clinical development. Chronic lymphocytic leukemia (CLL) may be especially amenable to TLR agonists because it is an immunologically susceptible tumor with strong expression of several TLRs, particularly TLR-7 and TLR-9. TLR agonists may indirectly clear CLL cells by enhancing the activity of natural killer and tumor-reactive T cells, or by altering the tumor microenvironment and inhibiting angiogenesis. However, signaling pathways can be activated directly in CLL cells by TLR-7 and TLR-9 agonists, leading to the production of cytokines and costimulatory molecules in a manner that is dependent on the underlying cytogenetic abnormalities, but rendering the tumor cells more sensitive to killing by cytotoxic T cells, immunotoxins and some chemotherapeutic drugs. Imidazoquinolines are TLR-7 agonists with strong local activity against CLL, and phase I trials of systemically administered imidazoquinolines (and also cytosine-phosphate-guanosine oligonucleotides that are TLR-9 agonists) are currently ongoing at different centers. The potential importance of these TLR agonists in the treatment of CLL is suggested by their ability to sensitize tumor cells to cytotoxic agents, and their future probably lies in combination with radiotherapies, chemotherapies, monoclonal antibodies and cancer vaccines.

Sensitization of IL-2 Signaling through TLR-7 Enhances B Lymphoma Cell Immunogenicity

The innate ability of B lymphoma cells to escape control by tumor-reactive T cells must be overcome to develop effective immunotherapies for these diseases. Because signals from both the innate and adaptive immune systems direct the acquisition of strong immunogenicity by professional APCs, the effects of IL-2 and the TLR-7 agonist, S28690, on the immunogenic properties of chronic lymphocytic leukemia (CLL) B cells were studied. IL-2 with S28690 caused CLL cells to proliferate and increased their expression of B7-family members, production of TNF-alpha and IL-10, and levels of tyrosine-phosphorylated STAT-1 and STAT-3 proteins. S28690 increased CD25 expression on CLL cells and sensitized them to IL-2 signaling. However, IL-2 did not change TLR-7 expression or signaling in CLL cells. The ability to stimulate T cell proliferation required additional activation of protein kinase C, which inhibited tumor cell proliferation, "switched off" IL-10 production, and caused essentially all CLL cells (regardless of clinical stage) to acquire a CD83(high)CD80(high)CD86(high)CD54(high) surface phenotype marked by the activation of STAT-1 without STAT-3. These findings suggest that TLR-7 "licenses" human B cells to respond to cytokines of the adaptive immune system (such as IL-2) and provide a strategy to increase the immunogenicity of lymphoma cells for therapeutic purposes.

Immunomodulatory effects of Toll-like receptor-7 activation on chronic lymphocytic leukemia cells

Weak immunogenicity of chronic lymphocytic leukemia (CLL) cells may contribute to disease progression and inhibit effective immunotherapy. Accordingly, agents that enhance the immunogenicity of CLL cells may be useful in immunotherapeutic approaches to this disease. Since Toll-like receptors (TLRs) are major regulators of innate immunity and initiation of adaptive immunity, we studied the effects of viral pathogen associated molecular pattern agonists (that are recognized by TLRs) on the costimulatory phenotype and function of CLL cells. CLL cells (especially those with high endogenous expression of CD38) responded to TLR7-activating imidazoquinolines and guanosine analogs by increasing costimulatory molecule expression, producing inflammatory cytokines, and becoming more sensitive to killing by cytotoxic effectors. Additional activation of protein kinase C pathways increased the ability to stimulate T-cell proliferation, blocked phosphorylation of the transcription factor, signal transducer and activator of transcription (STAT)3, and resulted in the acquisition of a dendritic cell surface phenotype by TLR7-activated CLL cells. Normal B cells also responded to TLR7 activation by increasing costimulatory molecule expression and cytokine production. These findings suggest a potential role for TLR7 agonists in CLL immunotherapy.