Synergistic in vivo antitumor effect of the histone deacetylase inhibitor MS-275 in combination with interleukin 2 in a murine model of renal cell carcinoma

Vascular disruption in combination with mTOR inhibition in renal cell carcinoma

Renal cell carcinoma (RCC) is an angiogenesis-dependent and hypoxia-driven malignancy. As a result, there has been an increased interest in the use of antiangiogenic agents for the management of RCC in patients. However, the activity of tumor-vascular disrupting agents (tumor-VDA) has not been extensively examined against RCC. In this study, we investigated the therapeutic efficacy of the tumor-VDA ASA404 (DMXAA, 5,6-dimethylxanthenone-4-acetic acid, or vadimezan) in combination with the mTOR inhibitor everolimus (RAD001) against RCC. In vitro studies were carried out using human umbilical vein endothelial cells and in vivo studies using orthotopic RENCA tumors and immunohistochemical patient tumor-derived RCC xenografts. MRI was used to characterize the vascular response of orthotopic RENCA xenografts to combination treatment. Therapeutic efficacy was determined by tumor growth measurements and histopathologic evaluation. ASA404/everolimus combination resulted in enhanced inhibition of endothelial cell sprouting in the 3-dimensional spheroid assay. MRI of orthotopic RENCA xenografts revealed an early increase in permeability 4 hours posttreatment with ASA404, but not with everolimus. Twenty-four hours after treatment, a significant reduction in blood volume was observed with combination treatment. Correlative CD31/NG2 staining of tumor sections confirmed marked vascular damage following combination therapy. Histologic sections showed extensive necrosis and a reduction in the viable rim following combination treatment compared with VDA treatment alone. These results show the potential of combining tumor-VDAs with mTOR inhibitors in RCC. Further investigation into this novel combination strategy is warranted.

Histone deacetylase inhibitors in the generation of the anti-tumour immune response

Acetylation of lysine residues acts to modify the function of a wide range of proteins. In histones, it affects chromatin structure, which can impact gene transcription, whereas acetylation of transcription factors and heat-shock proteins affect their activity. Deacetylase inhibitors block the dynamic turnover of acetylation resulting in hyperacetylation of target proteins. This can affect a wide range of cellular functions, and in a wide range of tumour cell types promote cytostatic and cytotoxic effects, but has little effect on normal cells. The inhibitors are being used clinically as anti-cancer agents. Although direct effects of the histone deacetylase (HDAC) inhibitors on cancers are beginning to be elucidated, the prospect of concurrent stimulation of the immune response raises hopes for immune attack of the tumour as part of the initial anti-cancer therapy and long-term immune-surveillance of residual or recurrent tumour. This review will examine the evidence for the generation of anti-tumour immunity after treatment of cancers with HDAC inhibitors.

Role of immunotherapy for renal cell cancer in 2011

High-dose interleukin-2 (IL-2) and interferon were the most commonly administered therapies before the recent introduction of targeted agents, including vascular endothelial growth factor and mammalian target of rapamycin pathway inhibitors. Although the new agents result in a progression-free survival benefit, high-dose IL-2 remains the only agent with proven efficacy in producing durable complete and partial responses in patients with metastatic renal cell carcinoma (RCC). Furthermore, although the use of single-agent interferon has decreased significantly since the introduction of targeted therapy, it remains in the frontline setting in combination with bevacizumab as a result of 2 large phase III trials. Lastly, improved understanding of immune regulation has led to the advancement of targeted immunotherapy using immune checkpoint inhibitors that have shown promising activity and are moving forward in clinical development. This article focuses on the current status of immunotherapy in the management of metastatic RCC.

Class I histone deacetylases 1, 2 and 3 are highly expressed in classical Hodgkin's lymphoma

OBJECTIVE

HDAC inhibitors (HDI) are anti-neoplastic drugs with preliminary successful clinical applications in Hodgkin's lymphoma (HL). Systematic investigations of HDAC expression in HL, based on histology and immunohistochemistry are yet rare.

RESEARCH DESIGN/METHODS

We investigated the expression of HDAC1, 2 and 3 in 283 HL on tissue microarrays.

MAIN OUTCOME MEASURES

Expression of HDAC isoforms was scored in Hodgkin and Reed-Sternberg cells (HRSC) and background infiltrate and compared with freedom of treatment failure (FTF) in 118 cases, for which all data was available.

RESULTS

All analyzable HL expressed the HDAC isoforms 2 (n = 194) and 3 (n = 207) in over 50%, mostly 100%, of HRSC and almost all background lymphocytes. HDAC1 was expressed in 169 of 179 analyzable HL in a mean of 82% and in 172 out of 179 analyzable cases in a mean of 83% of infiltrating lymphocytes. HDAC1 of below 75% in HRSC correlated with worse FTF with 16 out of 32 events, compared with 16 out of 82 in cases with over 75% HDAC1-expressing HRSC.

CONCLUSION

HDAC isoforms 1, 2 and 3 are highly expressed in HL. In addition, decreased HDAC1 expression is accompanied by worse outcome in HL.

A B-cell lymphoma vaccine using a depot formulation of interleukin-2 induces potent antitumor immunity despite increased numbers of intratumoral regulatory T cells

Therapeutic vaccination holds great potential as complementary treatment for non-Hodgkin's lymphoma. Here, we report that a therapeutic whole cell vaccine formulated with IL-2 adsorbed onto aluminum hydroxide as cytokine-depot formulation elicits potent antitumor immunity and induces delayed tumor growth, control of tumor dissemination and longer survival in mice challenged with A20-lymphoma. Therapeutic vaccination induced higher numbers of tumor's infiltrating lymphocytes (CD4(+) and CD8(+) T cells and NK cells), and the production of IFN-gamma and IL-4 by intratumoral CD4(+) T cells. Further, strong tumor antigen-specific cellular responses were detected at systemic level. Both the A20-derived antigenic material and the IL-2 depot formulation were required for induction of an effective immune response that impacted on cancer progression. All mice receiving any form of IL-2, either as part of the vaccine or alone as control, showed higher numbers of CD4(+)CD25(+/high)Foxp3(+) regulatory T cells (Treg) in the tumor, which might have a role in tumor progression in these animals. Nevertheless, for those animals that received the cytokine as part of the vaccine formulation, the overall effect was improved immune response and less disseminated disease, suggesting that therapeutic vaccination overcomes the potential detrimental effect of intratumoral Treg cells. Overall, the results presented here show that a simple vaccine formulation, that can be easily prepared under GMP conditions, is a promising strategy to be used in B-cell lymphoma and may have enough merit to be tested in clinical trials.

Establishment and characterization of transplantable, luminescence labeled rat renal cell carcinoma cell lines

PURPOSE

Since renal cell carcinoma is considered an immunogenic tumor, testing therapeutic strategies has been impeded by the lack of relevant tumor models in immunocompetent animals. Recent advances in bioluminescence imaging permit sensitive in vivo detection and quantification of cells emitting light. Thus, we established bioluminescent rat renal cell carcinoma cell lines for immunocompetent rats.

MATERIALS AND METHODS

The rat renal cell carcinoma cell line ACI-RCC stemming from chemically induced renal cell carcinoma in syngeneic ACI rats was stably transfected with a recombinant retroviral vector encoding luciferase genes derived from fireflies (ACI-RCC-ffLuc) or click beetles (ACI-RCC-cbLuc). Cell line growth patterns were characterized by bioluminescence imaging.

RESULTS

Linear correlations noted observed between cell number and photon counts in each cell type. ACI-RCC-cbLuc emitted light about 500-fold higher than ACI-RCC-ffLuc. When transplanted subcutaneously, only ACI-RCC-ffLuc grew, possibly because of less antigenicity. ACI-RCC-ffLuc photon emission correlated significantly with subcutaneous tumor size. Orthotopic tumor growth and subsequent metastatic spread were monitored with time by increased photon intensity on bioluminescence imaging. Based on ACI-RCC-cbLuc bioluminescent intensity the in vitro screening test allowed the identification of several anticancer agents, including molecules related to human renal cell carcinoma progression.

CONCLUSIONS

The new in vivo rat renal cell carcinoma model with luciferase labeled tumor cells allowed us to monitor tumor growth noninvasively and semiquantitatively by bioluminescence imaging. This model system coupled with in vitro screening permits precise evaluation of tumor behavior in intact animals and determination of the therapeutic efficacy of anticancer agents for renal cell carcinoma.

Enhanced antitumor activity induced by adoptive T-cell transfer and adjunctive use of the histone deacetylase inhibitor LAQ824

Tumors grow in the presence of antigen-specific T cells, suggesting the existence of intrinsic cancer cell escape mechanisms. We hypothesized that a histone deacetylase (HDAC) inhibitor could sensitize tumor cells to immunotherapy because this class of agents has been reported to increase tumor antigen expression and shift gene expression to a proapoptotic milieu in cancer cells. To test this question, we treated B16 murine melanoma with the combination of the HDAC inhibitor LAQ824 and the adoptive transfer of gp100 melanoma antigen-specific pmel-1 T cells. The combined therapy significantly improved antitumor activity through several mechanisms: (a) increase in MHC and tumor-associated antigen expression by tumor cells; (b) decrease in competing endogenous lymphocytes in recipient mice, resulting in a proliferative advantage for the adoptively transferred cells; and (c) improvement in the functional activity of the adoptively transferred lymphocytes. We confirmed the beneficial effects of this HDAC inhibitor as a sensitizer to immunotherapy in a different model of prophylactic prime-boost vaccination with the melanoma antigen tyrosinase-related protein 2, which also showed a significant improvement in antitumor activity against B16 melanoma. In conclusion, the HDAC inhibitor LAQ824 significantly enhances tumor immunotherapy through effects on target tumor cells as well as improving the antitumor activity of tumor antigen-specific lymphocytes.

An HDAC inhibitor enhances the antitumor activity of a CMV promoter-driven DNA vaccine

The cytomegalovirus (CMV) promoter is considered to be one of the strongest promoters for driving the in vivo expression of genes encoded by DNA vaccines. However, the efficacy of DNA vaccines has so far been disappointing (particularly in humans), and this might be explained in part by histone deacetylase (HDAC)-mediated chromatin condensation. Hence, we sought to investigate whether increasing the expression of DNA vaccine antigens with the HDAC inhibitor OSU-HDAC42 would enhance the efficacy of DNA vaccines in vivo. A luciferase assay was used to determine the effects of OSU-HDAC42 on CMV promoter-driven DNA plasmids in vitro and in vivo. Three HDAC inhibitors were able to activate expression from the CMV promoter in NIH3T3 cells and MBT-2 bladder cancer cells. The expression of luciferase was significantly enhanced by co-administration of pCMV-luciferase and OSU-HDAC42 in mice. To explore whether OSU-HDAC42 could enhance the specific antitumor activity of a neu DNA vaccine driven by the CMV promoter, we evaluated therapeutic effects and immune responses in a mouse tumor natively overexpressing HER2/neu. Mice receiving OSU-HDAC42 in combination with the CMV-promoter neu DNA vaccine exhibited stronger antitumor effects than mice given the DNA vaccine only. In addition, a correlation between the antitumor effects and the specific cellular immune responses was observed in the mice receiving the DNA vaccine and OSU-HDAC42.

Three epigenetic drugs up-regulate homeobox gene Rhox5 in cancer cells through overlapping and distinct molecular mechanisms

Epigenetic therapy of cancer using inhibitors of DNA methyltransferases (DNMT) or/and histone deacetylases (HDACs) has shown promising results in preclinical models and is being investigated in clinical trials. Homeodomain proteins play important roles in normal development and carcinogenesis. In this study, we demonstrated for the first time that an epigenetic drug could up-regulate homeobox genes in the reproductive homeobox genes on chromosome X (Rhox) family, including murine Rhox5, Rhox6, and Rhox9 and human RhoxF1 and RhoxF2 in breast, colon, and other types of cancer cells. We examined the molecular mechanisms underlining selective induction of Rhox5 in cancer cells by three epigenetic drugs: 5-aza-2'-deoxycytidine (DAC; decitabine), arsenic trioxide (ATO), and MS-275 [entinostat; N-(2-aminophenyl)-4-[N-(pyridine-3-ylmethoxy-carbonyl)aminomethyl]benzamide]. DAC induced Rhox5 mRNA expression from both distal promoter (Pd) and proximal promoter, whereas MS-275 and ATO induced gene expression from the Pd only. DAC and ATO inhibited both DNMT1 and DNMT3B protein expression, whereas MS-275 significantly reduced DNMT3B protein. In contrast to DAC, neither MS-275 nor ATO induced DNA demethylation on the Pd region. All three drugs led to enhanced acetylation of histones H3 and H4 at the promoter region. The occupancy of the activating histone mark dimethylated lysine 4 of H3 at Pd was enhanced by DAC and MS-275 but not ATO. Because they modulate gene expression with different potencies through shared and distinct epigenetic mechanisms, these epigenetic drugs may possess great potential in different applications for epigenetic therapy of cancer and other diseases.

The HDAC inhibitor panobinostat (LBH589) inhibits mesothelioma and lung cancer cells in vitro and in vivo with particular efficacy for small cell lung cancer

Lung cancer is the leading cause of cancer deaths in the United States. Current therapies are inadequate. Histone deacetylase inhibitors (HDACi) are a recently developed class of anticancer agents that cause increased acetylation of core histones and nonhistone proteins leading to modulation of gene expression and protein activity involved in cancer cell growth and survival pathways. We examined the efficacy of the HDACi panobinostat (LBH589) in a wide range of lung cancers and mesotheliomas. Panobinostat was cytotoxic in almost all 37 cancer cell lines tested. IC(50) and LD(50) values were in the low nmol/L range (4-470 nmol/L; median, 20 nmol/L). Small cell lung cancer (SCLC) cell lines were among the most sensitive lines, with LD(50) values consistently <25 nmol/L. In lung cancer and mesothelioma animal models, panobinostat significantly decreased tumor growth by an average of 62% when compared with vehicle control. Panobinostat was equally effective in immunocompetent and severe combined immunodeficiency mice, indicating that the inhibition of tumor growth by panobinostat was not due to direct immunologic effects. Panobinostat was, however, particularly effective in SCLC xenografts, and the addition of the chemotherapy agent etoposide augmented antitumor effects. Protein analysis of treated tumor biopsies revealed elevated amounts of cell cycle regulators such as p21 and proapoptosis factors, such as caspase 3 and 7 and cleaved poly[ADP-ribose] polymerase, coupled with decreased levels of antiapoptotic factors such as Bcl-2 and Bcl-X(L). These studies together suggest that panobinostat may be a useful adjunct in the treatment of thoracic malignancies, especially SCLC.

The short chain fatty acid butyrate induces promoter demethylation and reactivation of RARbeta2 in colon cancer cells

It has been proposed that cancer prevention results from multiple dietary agents acting together as "action packages." Here we obtain evidence that butyrate, which is generated from dietary fiber, enhances the responsiveness of colon cancer cells to all-trans retinoic acid (ATRA). Evidence was obtained that this interaction depends on histone deactylase one (HDAC1) inhibition by butyrate and retinoic acid receptor alpha (RARalpha) activation by ATRA. The enhancement of RAR beta 2 (RARbeta2) activation was accompanied by a rapid demethylation of the RARbeta2 promoter. This demethylation could be achieved by butyrate alone, and it differed from that triggered by the DNA methyltransferase inhibitor 5-Aza-2' deoxycytidine in that it was 1) sporadic on the RARbeta2 promoter, 2) not genome wide, and 3) independent of extensive DNA replication. An analysis of inter-methylated sites assay indicated that only a few percent of loci analyzed showed reduced methylation. In colon cancer cells that were particularly resistant to RARbeta2 reactivation, the actions of butyrate could be further enhanced by the soy isoflavone genistein, which has also been reported to work through an epigenetic mechanism. These data suggest that dietary compounds that modulate epigenetic programming are likely to function best in the presence of retinoids and other cancer-preventing compounds that are sensitive to a cell's epigenetic state.

Class I histone deacetylases 1, 2 and 3 are highly expressed in renal cell cancer

BACKGROUND

Enhanced activity of histone deacetylases (HDAC) is associated with more aggressive tumour behaviour and tumour progression in various solid tumours. The over-expression of these proteins and their known functions in malignant neoplasms has led to the development of HDAC inhibitors (HDI) as new anti-neoplastic drugs. However, little is known about HDAC expression in renal cell cancer.

METHODS

We investigated the expression of HDAC 1, 2 and 3 in 106 renal cell carcinomas and corresponding normal renal tissue by immunohistochemistry on tissue micro arrays and correlated expression data with clinico-pathological parameters including patient survival.

RESULTS

Almost 60% of renal cell carcinomas expressed the HDAC isoforms 1 and 2. In contrast, HDAC 3 was only detected in 13% of all renal tumours, with particular low expression rates in the clear cell subtype. HDAC 3 was significantly higher expressed in pT1/2 tumours in comparison to pT3/4 tumours. Expression of class I HDAC isoforms correlated with each other and with the proliferative activity of the tumours. We found no prognostic value of the expression of any of the HDAC isoforms in this tumour entity.

CONCLUSION

Class I HDAC isoforms 1 and 2 are highly expressed in renal cell cancer, while HDAC 3 shows low, histology dependent expression rates. These unexpected differences in the expression patterns suggests alternative regulatory mechanisms of class I HDACs in renal cell cancer and should be taken into account when trials with isoform selective HDI are being planned. Whether HDAC expression in renal cancers is predictive of responsiveness for HDI will have to be tested in further studies.

Histone deacetylase inhibitors in cancer therapy

PURPOSE OF REVIEW

The purpose of this review is to provide an overview of recent advances in the development of histone deacetylase inhibitors (HDACi) for the treatment of cancer.

RECENT FINDINGS

Recently, there has been a dramatic expansion of HDACi clinical investigation. There are now 11 HDACi in clinical trial, including inhibitors with a broad spectrum of HDAC isoform inhibitory activity as well as drugs with isoform selectivity. Over 70 combination therapy trials are in progress. Major areas of progress covered include the entry of new HDAC inhibitors into clinical development, recent progress in understanding of molecular mechanisms of HDACi anticancer activity, and a preclinical and clinical update on HDACi in combination.

SUMMARY

In the period under review there have been advances in understanding of HDACi mechanisms of action, identification of rational combinations that address increased efficacy and overcoming resistance, and greatly expanded clinical development of pan-HDAC-inhibitory and isoform-selective inhibitors in monotherapy and combination therapy protocols.

Regulatory T cells and treatment of cancer

CD4+CD25+FOXP3+ regulatory T cells (Tregs) are elevated in cancers and can thwart protective antitumor immunity. Recent human cancer trials suggest that depleting Tregs can be clinically beneficial. Additional types of deleterious regulatory cells are also increased in cancer. Tregs also play unanticipated roles in cancer therapy in that some drugs unexpectedly increase (e.g. cancer vaccines or IL-2 treatment) or decrease (e.g. antineoangiogenesis agents or receptor tyrosine kinase inhibitors) their numbers or function. Managing deleterious effects of regulatory cells represents a novel and potentially effective way to give immunotherapy for cancer. New insights into molecular mechanisms governing trafficking, differentiation, and function of these cells suggest novel approaches to manipulating them as treatment strategies.