Antibody dependent cellular cytotoxicity-inducing anti-EGFR antibodies as effective therapeutic option for cutaneous melanoma resistant to BRAF inhibitors

Introduction

About 50% of cutaneous melanoma (CM) patients present activating BRAF mutations that can be effectively targeted by BRAF inhibitors (BRAFi). However, 20% of CM patients exhibit intrinsic drug resistance to BRAFi, while most of the others develop adaptive resistance over time. The mechanisms involved in BRAFi resistance are disparate and globally seem to rewire the cellular signaling profile by up-regulating different receptor tyrosine kinases (RTKs), such as the epidermal growth factor receptor (EGFR). RTKs inhibitors have not clearly demonstrated anti-tumor activity in BRAFi resistant models. To overcome this issue, we wondered whether the shared up-regulated RTK phenotype associated with BRAFi resistance could be exploited by using immune weapons as the antibody-dependent cell cytotoxicity (ADCC)-mediated effect of anti-RTKs antibodies, and kill tumor cells independently from the mechanistic roots.

Methods and results

By using an in vitro model of BRAFi resistance, we detected increased membrane expression of EGFR, both at mRNA and protein level in 4 out of 9 BRAFi-resistant (VR) CM cultures as compared to their parental sensitive cells. Increased EGFR phosphorylation and AKT activation were observed in the VR CM cultures. EGFR signaling appeared dispensable for maintaining resistance, since small molecule-, antibody- and CRISPR-targeting of EGFR did not restore sensitivity of VR cells to BRAFi. Importantly, immune-targeting of EGFR by the anti-EGFR antibody cetuximab efficiently and specifically killed EGFR-expressing VR CM cells, both in vitro and in humanized mouse models in vivo, triggering ADCC by healthy donors' and patients' peripheral blood cells.

Conclusion

Our data demonstrate the efficacy of immune targeting of RTKs expressed by CM relapsing on BRAFi, providing the proof-of-concept supporting the assessment of anti-RTK antibodies in combination therapies in this setting. This strategy might be expected to concomitantly trigger the crosstalk of adaptive immune response leading to a complementing T cell immune rejection of tumors.

Autophagy in BRAF-mutant cutaneous melanoma: recent advances and therapeutic perspective

Macroautophagy, hereafter referred to as autophagy, represents a highly conserved catabolic process that maintains cellular homeostasis. At present, the role of autophagy in cutaneous melanoma (CM) is still controversial, since it appears to be tumor-suppressive at early stages of malignant transformation and cancer-promoting during disease progression. Interestingly, autophagy has been found to be often increased in CM harboring BRAF mutation and to impair the response to targeted therapy. In addition to autophagy, numerous studies have recently conducted in cancer to elucidate the molecular mechanisms of mitophagy, a selective form of mitochondria autophagy, and secretory autophagy, a process that facilitates unconventional cellular secretion. Although several aspects of mitophagy and secretory autophagy have been investigated in depth, their involvement in BRAF-mutant CM biology has only recently emerged. In this review, we aim to overview autophagy dysregulation in BRAF-mutant CM, along with the therapeutic advantages that may arise from combining autophagy inhibitors with targeted therapy. In addition, the recent advances on mitophagy and secretory autophagy involvement in BRAF-mutant CM will be also discussed. Finally, since a number of autophagy-related non-coding RNAs (ncRNAs) have been identified so far, we will briefly discussed recent advances linking ncRNAs to autophagy regulation in BRAF-mutant CM.

Emerging Role of Immunomonitoring to Predict the Clinical Outcome of Patients With Malignant Pleural Mesothelioma Treated With Radical Radiation Therapy

PURPOSE

The present study aimed at evaluating the baseline immune profile and the immunomodulating effects of radical hemithoracic radiation therapy (RT) in patients affected by malignant pleural mesothelioma (MPM) to identify potential predictive biomarkers of therapy response, toxicity development, and eligibility for further immunotherapeutic treatments.

METHODS AND MATERIALS

Blood samples were collected from 55 patients with MPM, enrolled in a phase 3 trial comparing radical hemithoracic RT (interventional arm, n = 28) with local palliative RT (control arm, n = 27). Immunomonitoring was performed before RT, at the end of treatment, and 1 month after therapy, characterizing natural killer cells, B and T lymphocytes, activated CD4 and CD8 T cells, interferon-γ- and tumor necrosis factor-α-producing T helper (Th) 1 cells, regulatory T cells, and Th17 and Th22 lymphocytes, through flow cytometry. Serum levels of interleukin (IL)-6, -8, -10 and mesothelin were quantified through Enzyme-Linked Immunosorbent Assay (ELISA) assays at the same time points. Variations in the immune parameters were investigated by Friedman test and Wilcoxon signed rank post hoc test with Bonferroni correction for multiple testing, while the prognostic effect of immune biomarkers was evaluated through Kaplan-Meier method and Spearman's correlation analysis.

RESULTS

Major immune variations were noticed after radical RT compared with palliative treatment, in particular an improvement in activated T cells and in interferon-γ-producing Th1 cells after RT. In the interventional arm, baseline high levels of Th22 and IL-10 and an increase in T cells were associated with an improved survival, whereas a fold increase in serum mesothelin correlated with the development of severe toxicity. An improvement of immunosuppressive regulatory T cells was observed in both arms of treatment.

CONCLUSIONS

The immunomonitoring performed in patients with MPM revealed potential prognostic biomarkers for radical hemithoracic RT treatment and identified specific immune signatures induced by RT immunomodulation, which could suggest a synergistic effect with an immunotherapeutic treatment.

The pleiotropic roles of circular and long noncoding RNAs in cutaneous melanoma

Cutaneous melanoma (CM) is a very aggressive disease, often characterized by unresponsiveness to conventional therapies and high mortality rates worldwide. The identification of the activating BRAFV600 mutations in approximately 50% of CM patients has recently fueled the development of novel small-molecule inhibitors that specifically target BRAFV600 -mutant CM. In addition, a major progress in CM treatment has been made by monoclonal antibodies that regulate the immune checkpoint inhibitors. However, although target-based therapies and immunotherapeutic strategies have yielded promising results, CM treatment remains a major challenge. In the last decade, accumulating evidence points to the aberrant expression of different types of noncoding RNAs (ncRNAs) in CM. While studies on microRNAs have grown exponentially leading to significant insights on CM biology, the role of circular RNAs (circRNAs) and long noncoding RNAs (lncRNAs) in this tumor is less understood, and much remains to be discovered. Here, we summarize and critically review the available evidence on the molecular functions of circRNAs and lncRNAs in BRAFV600 -mutant CM and CM immunogenicity, providing recent updates on their functional role in targeted therapy and immunotherapy resistance. In addition, we also include an evaluation of several algorithms and databases for prediction and validation of circRNA and lncRNA functional interactions.

Long Noncoding RNAs as Innovative Urinary Diagnostic Biomarkers

The characterization of circulating tumor cells (CTCs) is now widely studied as a promising source of cancer-derived biomarkers because of their role in tumor formation and progression. However, CTCs analysis presents some limitations and no standardized method for CTCs isolation from urine has been defined so far. In fact, besides blood, urine represents an ideal source of noninvasive biomarkers, especially for the early detection of genitourinary tumors. Besides CTCs, long noncoding RNAs (lncRNAs) have also been proposed as potential noninvasive biomarkers, and the evaluation of the diagnostic accuracy of urinary lncRNAs has dramatically increased over the last years, with many studies being published. Therefore, this review provides an update on the clinical utility of urinary lncRNAs as novel biomarkers for the diagnosis of bladder and prostate cancers.

Abstract B06: Loss of SPRY1 expression in BRAF-mutant cutaneous melanoma inhibits cell proliferation and improves response to targeted therapy

Background: Targeted therapy has proven efficacy in BRAF-mutant metastatic cutaneous melanoma (CM), but patients almost invariantly develop an early resistance. Although the underlying mechanisms are various and heterogeneous, resistance usually associates with an altered signaling. Sprouty 1 (SPRY1) has been described as an upstream mediator of MAPK signaling pathway, and although it has been found to be implicated in different biologic processes, its specific role in BRAF-mutant CM has been only partially addressed.

Material and Methods: SPRY1 expression was assessed by quantitative real-time RT-PCR (qRT-PCR) and Western blotting (WB) analyses in BRAF-mutant CM cell lines and tissues. SPRY1 gene was knocked out using CRISPR-strategy. WB analyses evaluated the modulation of MAPK signaling pathways in SPRY1 knockout (SPRY1KO) clones. RNA-seq identified mRNAs that were differentially expressed in SPRY1KO clones respect to parental cells, and their expression was then validated by qRT-PCR. To further compare SPRY1KO clones to parental cells, cell proliferation was measured using xCELLigence instrument, whereas cell cycle progression, ROS induction, and apoptosis were assessed by flow cytometry. In vivo effects of SPRY1 silencing were investigated in xenografted mice treated with or without BRAF inhibitor (BRAFi).

Results: SPRY1 was found highly expressed in a panel of BRAF-mutant CM cell lines and tissues, both at mRNA and protein level. To investigate the biologic role of SPRY1 in BRAF-mutant CM, SPRY1KO clones were obtained from 3 CM cell lines. RNA-seq identified 38 mRNAs that were significantly commonly modulated in SPRY1KO clones respect to parental cells. Ingenuity Pathway Analysis indicated that the top of the neighbor coding gene function of differentially expressed mRNAs was involved in cell proliferation and cell death. In addition, WB assays showed SPRY1 silencing was associated with i) decreased activation of p38 MAPK and beta-catenin signaling, ii) reduced expression of metalloproteinase 2, and iii) increased levels of p53. Consistent with these data, SPRY1 silencing markedly induced cell cycle arrest and apoptosis, repressed cell proliferation in vitro, and impaired tumor growth in vivo. In addition, SPRY1 knockdown associated with improved response to BRAFi both in vitro and in vivo, which could be partly contributed by the higher levels of ROS observed in SPRY1KO clones. Interestingly, BRAFi treatment reduced mRNA and protein SPRY1 levels in parental BRAF-mutant CM cell lines, indicating that SPRY1 expression is downstream of the MEK-ERK signaling. Of note, some of the effects induced by BRAFi in parental cells were similar to those observed in SPRY1KO clones, suggesting that BRAFi activity may at least in part rely on SPRY1 downregulation.

Conclusions: All together, our findings reveal important insights into SPRY1 role in BRAF-mutant CM and suggest its potential involvement in targeted therapy response.

Citation Format: Barbara Montico, Giorgio Giurato, Francesca Colizzi, Alessia Covre, Elisa Comaro, Eliana Pivetta, Dania Benedetti, Alessandro Weisz, Agostino Steffan, Michele Maio, Luca Sigalotti, Elisabetta Fratta. Loss of SPRY1 expression in BRAF-mutant cutaneous melanoma inhibits cell proliferation and improves response to targeted therapy [abstract]. In: Proceedings of the AACR Special Conference on Melanoma: From Biology to Target; 2019 Jan 15-18; Houston, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(19 Suppl):Abstract nr B06.

Abstract 1794: Loss of Spry1 reduces growth of BRAFV600-mutant cutaneous melanoma and improves response to targeted therapy

Introduction: Targeted therapies have recently revolutionized the treatment of BRAFV600-mutant metastatic cutaneous melanoma (CM). However, most patients do not achieve tumor regression at all due to the occurrence of resistance mechanisms. Mitogen-activated protein kinase (MAPK) pathway activation is a central step in BRAFV600-mutant CM pathogenesis and a better understanding of molecular mechanisms involved MAPK modulation is necessary to develop more effective therapeutic strategies. In the last years, Spry1 has been frequently described as an upstream regulator of MAPK signaling pathway, but its specific role in BRAFV600-mutant CM is still poorly defined.

Materials and methods: Autologous BRAFV600-mutant CM cell cultures were generated from CM patients resected in our institution. The expression of Spry1 was evaluated by quantitative real-time PCR (qRT-PCR) and Western blot (WB) analyses. Spry1 gene was knock out using CRISPR. RNA-seq identified mRNAs commonly differentially expressed in Spry1 knock-out (Spry1KO) clones, and their expression was further validated by qRT-PCR. WB analyses evaluated the modulation of MAPK signaling pathways in Spry1KO clones. Cell proliferation was measured using xCELLigence instrument, whereas cell cycle progression, ROS induction, and apoptosis were assessed by flow cytometry. In vivo effects of Spry1 silencing were investigated in xenograft mice treated with or without BRAF inhibitor (BRAFi).

Results: The expression of Spry1 in human CM was explored using publicly available cancer gene expression profiling and transcriptome sequencing data. mRNA expression of Spry1 was significantly elevated in metastatic CM respect to primary tumors and mRNA levels of Spry1 were significantly up-regulated in metastatic CM compared with primary lesions. The function of Spry1 was evaluated by comparing three BRAFV600-mutant CM cell lines and the respective Spry1KO cells. We found that Spry1KO induced cell cycle arrest and apoptosis, repressed cell proliferation in vitro, and impaired tumor growth in vivo. Moreover Spry1KO was found to impair the expression of several markers of epithelial-mesenchimal transition. In addition, ERK1/2 was found hyperactivated together with p38 leading to an increase in basal ROS levels in Spry1KO clones. This suggests that BRAFV600-mutant CM may restrain the activity of Spry1 to avoid oncogenic stress and to enable tumor growth. Indeed, treatment with the BRAFi vemurafenib down-regulated Spry1 levels in parental CM cell lines, indicating that Spry1 expression is sustained by MAPK/ERK signaling pathway in a positive feedback loop that safeguards cells from the potentially toxic effects of ERK1/2 hyperactivation. Disruption of this feedback loop rendered Spry1KO cells more susceptible to apoptosis and markedly improved response to BRAFi both in vitro and in vivo, as a consequence of the detrimental effect of ERK1/2 hyperactivation observed upon Spry1 abrogation.

Conclusions: All together, our data strongly suggest that targeting Spry1 might offer a treatment strategy for BRAFV600-mutant CM by inducing the toxic effects of ERK-mediated signaling.

Citation Format: Barbara Montico, Francesca Colizzi, Giorgio Giurato, Aurora Rizzo, Annamaria Salvati, Lorena Baboci, Dania Benedetti, Eliana Pivetta, Alessia Covre, Michele Dal Bo, Alessandro Weisz, Agostino Steffan, Michele Maio, Luca Sigalotti, Elisabetta Fratta. Loss of Spry1 reduces growth of BRAFV600-mutant cutaneous melanoma and improves response to targeted therapy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1794.

Abstract 1839: Suppression of Spry1 sensitizes cutaneous melanoma to BRAF-targeted therapy

Background: About 50% of cutaneous melanoma (CM) harbor the activating BRAFV600E mutation, which exerts most of the oncogenic effects through the activation of the MAPK signaling pathways. BRAF inhibitors (BRAFi) have showed important clinical activities in CM, but their effectiveness is impaired by the emergence of an early drug resistance. Accordingly, a better understanding of the molecular basis of BRAFi resistance may provide insights useful to develop new therapeutic strategies in CM. Spry gene family includes four members (Spry1-4), which differ in their tissue distribution, activity and interaction partners, thus suggesting nonredundant functions. Although interactions between Spry proteins and several MAPK pathway components have been reported, the specific role of Spry1 in CM has yet to be defined.

Methods: Bioinformatic analysis on data available on TCGA was performed using the pipeline suggested on the TCGA portal. Spry1 expression levels were measured in BRAFV600 mutant CM cell lines using quantitative real-time PCR (qRT-PCR) and Western blotting. CRISPR based strategy was used to knock out Spry1 gene in BRAFV600 mutant CM cell lines established in our Institution. Transfected cells were sorted into single cells and subsequently expanded. Spry1 knockout (Spry1KO) clones were validated by Sanger sequencing and Western blotting, respectively. Cell viabilities before and after BRAFi treatment were evaluated by MTT and clonogenic assays. Apoptosis was assessed by Annexin V/PI staining. Modulation of MAPK signaling pathways and apoptosis were examined by qRT-PCR and Western blotting. P53 nuclear translocation was evaluated through multispectral imaging flow cytometry analysis.

Results: Specific bioinformatic analysis, using TCGA, was performed to provide more information regarding pathways associated with MAPK signaling. Our analysis revealed that Spry proteins are differentially expressed in CM. In line with these findings, Spry1 was found high expressed in a panel of CM cell lines with BRAFV600 mutation both at mRNA and protein level. Preliminary data demonstrated that the expression and/or phosphorylation of key proteins involved in MAPK signaling were modulated in Spry1KO clones with respect to the parental cell line. Furthermore, Spry1 inactivation associated with: i) enhanced activation and nuclear translocation of the tumor suppressor p53, and ii) decreased mRNA and protein levels of several antiapoptotic proteins. Of note, the treatment of Spry1KO clones with BRAFi reduced CM cell survival in clonogenic assays, and induced apoptosis in a dose- and time-dependent manner. Further studies are ongoing in order to determine the molecular changes involved in Spry1KO clones in response to BRAFi treatment.

Conclusions: Our results suggest that Spry1 gene may exert oncogenic functions in CM and its upregulation can potentially contribute to BRAFi resistance.

Citation Format: Giorgio Giurato, Francesca Colizzi, Aurora Rizzo, Debora Martorelli, Barbara Montico, Katy Mastorci, Dania Benedetti, Alessandro Weisz, Riccardo Dolcetti, Sigalotti Luca, Elisabetta Fratta. Suppression of Spry1 sensitizes cutaneous melanoma to BRAF-targeted therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1839.

Epimutational profile of hematologic malignancies as attractive target for new epigenetic therapies

In recent years, recurrent somatic mutations in epigenetic regulators have been identified in patients with hematological malignancies. Furthermore, chromosomal translocations in which the fusion protein partners are themselves epigenetic regulators or where epigenetic regulators are recruited/targeted by oncogenic fusion proteins have also been described. Evidence has accumulated showing that "epigenetic drugs" are likely to provide clinical benefits in several hematological malignancies, granting their approval for the treatment of myelodysplastic syndromes and cutaneous T-cell lymphomas. A large number of pre-clinical and clinical trials evaluating epigenetic drugs alone or in combination therapies are ongoing. The aim of this review is to provide a comprehensive summary of known epigenetic alterations and of the current use of epigenetic drugs for the treatment of hematological malignancies.

Abstract 1196: Epigenetic drugs modulate long noncoding RNAs expression in BRAF inhibitor-resistant melanoma

Emergence of drug resistance is the major cause of failure of BRAF inhibitors (BRAFi) treatment in cutaneous melanoma (CM). Epigenetic modifications are known to physiologically trigger massive modifications in cellular commitment and several studies report a correlation between the drug-resistant phenotype and epigenetic alterations of tumor cells. In this setting, long noncoding RNAs (lncRNAs) represent a class of gene regulators acting at epigenetic, transcriptional and post-transcriptional level. Several studies have implicated lncRNAs in chemoresistance through their ability to impair cell cycle arrest and apoptosis, but also to induce and modulate epithelial-mesenchymal transition and cell adhesion-associated signaling pathways. LncRNAs interact with histone modifying complexes and/or DNA methyltransferases, being also targets of these epigenetic mediators. Furthermore, epigenetic drugs have been recently identified as modulators for lncRNAs function as well as their related targeting signals. Starting from these evidences, we asked the question whether epigenetic drugs could differentially affect the survival of BRAFi-resistant (VR) and -sensitive CM cells, investigating the mechanistic network involved, with a specific focus on the role of lncRNA. A panel of BRAFi-sensitive and VR CM cell lines was treated with the FDA-approved HDAC inhibitor vorinostat (SAHA). FACS analysis of annexin V-FITC/propidium iodide stained cells showed that SAHA cytotoxic activity was more pronounced on VR CM cells than on their parental counterparts. RNA-Seq analysis revealed that a large number of differentially expressed lncRNAs was modulated in VR CM cells treated with SAHA. Intriguingly, the expression of several VR up-regulated lncRNAs was decreased to levels similar to those observed in the matched parental cells. Functional analysis indicated these lncRNAs were statistically enriched in pathways involving cellular growth and proliferation, but also cellular assembly and organization. Though additional studies are required, epigenetic modulation of VR-associated lncRNAs promises to have significant therapeutic potential to restore BRAFi sensivity in CM, being concomitantly effective in killing VR cells as monotherapy. Based on our preliminary data, we could anticipate that the combined use of epigenetic and targeted drugs would increase therapeutic efficacy in CM patients relapsing to BRAFi.

Citation Format: Barbara Montico, Giorgio Giurato, Katy Mastorci, Aurora Rizzo, Maria Ravo, Francesca Rizzo, Alessandro Weisz, Riccardo Dolcetti, Francesca Colizzi, Luca Sigalotti, Elisabetta Fratta. Epigenetic drugs modulate long noncoding RNAs expression in BRAF inhibitor-resistant melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1196. doi:10.1158/1538-7445.AM2017-1196

Prognostic significance of LINE-1 hypomethylation in oropharyngeal squamous cell carcinoma

Background

Inclusion of new biomarkers to improve a personalized treatment approach for oropharyngeal squamous cell carcinoma (OPSCC) is urgently needed. Hypomethylation of the Long interspersed nucleotide element-1 (LINE-1) repetitive elements, a widely accepted surrogate of overall genomic DNA methylation content, was found to be associated with a poor prognosis in several cancers. At present, no studies have investigated the influence of LINE-1 methylation levels on OPSCC relapse. The main goal of this study was the evaluation of the prognostic value of LINE-1 methylation status in predicting early tumor relapse in locally advanced OPSCC.

Methods

We retrospectively reviewed a cohort of 77 patients with stage III–IVB OPSCC. Methylation of LINE-1 repetitive sequences was evaluated by real-time quantitative methylation-specific PCR in formalin-fixed paraffin-embedded tissues. The prognostic relevance of LINE-1 methylation was assessed by comparing patients who relapsed within 2 years from the end of treatment (cases) with those who did not (controls). Results were validated in an independent cohort of 33 patients with OPSCC.

Results

With respect to early OPSCC relapse, the mean LINE-1 methylation level was significantly lower in relapsed cases than in control group (p < 0.01). Interestingly, LINE-1 methylation was lower in relapsed cases than in controls in both HPV16-negative and HPV16-positive OPSCC patients, even if statistical significance was reached only for the former group (p = 0.01). LINE-1 methylation levels were also significantly reduced in relapsed cases with respect to the controls in OPSCC current smokers (p = 0.02). Consistently, in HPV16-negative current smokers, OPSCC relapse was significantly associated with decreased levels of LINE-1 methylation (p = 0.02). Using logistic regression model, we found that patients with hypomethylated LINE-1 were associated with a 3.5 higher risk of early relapse than hypermethylated ones (OR = 3.51; 95% CI 1.03–12.00). Adjustment for potential confounders did not substantially change the risk magnitude. Results from the validation cohort confirmed the lower LINE-1 methylation in patients who early relapsed compared to relapse-free patients.

Conclusions

LINE-1 hypomethylation is associated with higher risk of early relapse in stage III–IVB OPSCC. Further validation in a prospective study is needed for its application in daily clinical practice.

Antitumor activity of epigenetic immunomodulation combined with CTLA-4 blockade in syngeneic mouse models

The multifaceted immunomodulatory activity of DNA hypomethylating agents improves immunogenicity and immune recognition of neoplastic cells; thus, we predicted they could be utilized to design new immunotherapeutic combinations in cancer. Testing this hypothesis, the antitumor efficacy of the DNA hypomethylating agent 5-aza-2'-deoxycytidine (5-AZA-CdR) combined with the anti-CTLA-4 monoclonal antibody (mAb) 9H10 in syngeneic transplantable murine models was investigated. Murine mammary carcinoma TS/A or mesothelioma AB1 cells were injected in BALB/c, athymic nude, and SCID/Beige mice that were treated with 5-AZA-CdR, mAb 9H10, or their combination. Tumor volumes were captured at different time-points; molecular and immunohistochemical assays investigated changes in neoplastic and normal tissues. A significant antitumor effect of 5-AZA-CdR combined with mAb 9H10 was found: compared to controls, a 77% (p < 0.01), 54% (p < 0.01) and 33% (p = 0.2) decrease in TS/A tumor growth was induced by 5-AZA-CdR combined with mAb 9H10, 5-AZA-CdR or mAb 9H10, respectively. These antitumor activities were confirmed utilizing the AB1 model. 5-AZA-CdR-based regimens induced a promoter-demethylation-sustained tumor expression of cancer testis antigens. MHC class I expression was up-regulated by 5-AZA-CdR. Antitumor efficacy of 5-AZA-CdR in athymic nude and SCID/Beige mice was not increased by mAb 9H10. In BALB/c mice, combined treatment induced the highest tumor infiltration by CD3⁺ lymphocytes, which included both CD8⁺ and CD4⁺ T cells; no such infiltrates were observed in normal tissues. This significant immune-related antitumor activity of 5-AZA-CdR combined with CTLA-4 blockade, demonstrated in highly aggressive mouse tumor models, provides a strong scientific rationale to implement epigenetically-based immunotherapies in cancer patients.

Immunomodulatory activity of SGI-110, a 5-aza-2'-deoxycytidine-containing demethylating dinucleotide

PURPOSE

Pharmacologic DNA hypomethylation holds strong promises in cancer immunotherapy due to its immunomodulatory activity on neoplastic cells. Searching for more efficient DNA hypomethylating agents to be utilized to design novel immunotherapeutic strategies in cancer, we investigated the immunomodulatory properties of the new DNA hypomethylating agent SGI-110, that is resistant to in vivo inactivation by cytidine deaminase.

EXPERIMENTAL DESIGN

Cutaneous melanoma, mesothelioma, renal cell carcinoma, and sarcoma cells were treated in vitro with SGI-110. RT-PCR, quantitative RT-PCR, quantitative methylation-specific PCR, and flow cytometric analyses were performed to investigate changes induced by SGI-110 in the constitutive immune profile of cancer cells. The recognition by gp100-specific CTL of gp100-positive melanoma cells, treated or not with SGI-110, was tested by LDH release assays.

RESULTS

SGI-110 induced/up-regulated the expression of investigated cancer/testis antigens (CTA) (i.e., MAGE-A1, MAGE-A2, MAGE-A3, MAGE-A4, MAGE-A10, GAGE 1-2, GAGE 1-6, NY-ESO-1, and SSX 1-5) in all cancer cell lines studied, both at mRNA and at protein levels. Quantitative methylation-specific PCR analyses identified a hypomethylation of MAGE-A1 and NY-ESO-1 promoters in SGI-110-treated neoplastic cells, demonstrating a direct role of pharmacologic DNA demethylation in CTA induction. SGI-110 also up-regulated the expression of HLA class I antigens and of ICAM-1, resulting in an improved recognition of cancer cells by gp100-specific CTL.

CONCLUSIONS

Our findings show that SGI-110 is a highly attractive therapeutic agent to comprehensively increase immunogenicity and immune recognition of neoplastic cells, and provide the scientific rationale for its clinical development to design novel chemo-immunotherapeutic approaches in cancer patients.

Epigenetic remodelling of gene expression profiles of neoplastic and normal tissues: immunotherapeutic implications

BACKGROUND

Epigenetic remodelling of cancer cells is an attractive therapeutic strategy and distinct DNA hypomethylating agents (DHA) are being actively evaluated in patients with hemopoietic or solid tumours. However, no studies have investigated the modulation of gene expression profiles (GEP) induced by DHA in transformed and benign tissues. Such information is mandatory to clarify the fine molecular mechanism(s) underlying the clinical efficacy of DHA, to identify appropriate therapeutic combinations, and to address safety issues related to their demethylating potential in normal tissues. Thus, utilising a syngeneic mouse model, we investigated the remodelling of GEP of neoplastic and normal tissues induced by systemic administration of DHA.

METHODS

The murine mammary carcinoma cells TS/A were injected s.c. into female BALB/c mice that were treated i.p. with four cycles of the DHA 5-aza-2'-deoxycytidine (5-AZA-CdR) at a fractioned daily dose of 0.75 mg kg(-1) (q8 h × 3 days, every week). Whole mouse transcriptomes were analysed by microarrays in neoplastic and normal tissues from control and treated mice. Results were processed by bioinformatic analyses.

RESULTS

In all, 332 genes were significantly (P ≤ 0.05; FC ≥ 4) modulated (294 up and 38 downregulated) in neoplastic tissues from 5-AZA-CdR-treated mice compared with controls. In decreasing order of magnitude, changes in GEP significantly (P ≤ 0.05) affected immunologic, transport, signal transduction, spermatogenesis, and G-protein-coupled receptor protein signalling pathways. Epigenetic remodelling was essentially restricted to tumour tissues, leaving substantially unaltered normal ones.

CONCLUSION

The ability of 5-AZA-CdR to selectively target tumour GEP and its major impact on immune-related genes, strongly support the clinical use of DHA alone or combined with immunotherapeutic agents.

Whole genome methylation profiles as independent markers of survival in stage IIIC melanoma patients

Background

The clinical course of cutaneous melanoma (CM) can differ significantly for patients with identical stages of disease, defined clinico-pathologically, and no molecular markers differentiate patients with such a diverse prognosis. This study aimed to define the prognostic value of whole genome DNA methylation profiles in stage III CM.

Methods

Genome-wide methylation profiles were evaluated by the Illumina Human Methylation 27 BeadChip assay in short-term neoplastic cell cultures from 45 stage IIIC CM patients. Unsupervised K-means partitioning clustering was exploited to sort patients into 2 groups based on their methylation profiles. Methylation patterns related to the discovered groups were determined using the nearest shrunken centroid classification algorithm. The impact of genome-wide methylation patterns on overall survival (OS) was assessed using Cox regression and Kaplan-Meier analyses.

Results

Unsupervised K-means partitioning by whole genome methylation profiles identified classes with significantly different OS in stage IIIC CM patients. Patients with a “favorable” methylation profile had increased OS (P = 0.001, log-rank = 10.2) by Kaplan-Meier analysis. Median OS of stage IIIC patients with a “favorable” vs. “unfavorable” methylation profile were 31.5 and 10.4 months, respectively. The 5 year OS for stage IIIC patients with a “favorable” methylation profile was 41.2% as compared to 0% for patients with an “unfavorable” methylation profile. Among the variables examined by multivariate Cox regression analysis, classification defined by methylation profile was the only predictor of OS (Hazard Ratio = 2.41, for “unfavorable” methylation profile; 95% Confidence Interval: 1.02-5.70; P = 0.045). A 17 gene methylation signature able to correctly assign prognosis (overall error rate = 0) in stage IIIC patients on the basis of distinct methylation-defined groups was also identified.

Conclusions

A discrete whole-genome methylation signature has been identified as molecular marker of prognosis for stage IIIC CM patients. Its use in daily practice is foreseeable, and promises to refine the comprehensive clinical management of stage III CM patients.

Methylation levels of the "long interspersed nucleotide element-1" repetitive sequences predict survival of melanoma patients

Background

The prognosis of cutaneous melanoma (CM) differs for patients with identical clinico-pathological stage, and no molecular markers discriminating the prognosis of stage III individuals have been established. Genome-wide alterations in DNA methylation are a common event in cancer. This study aimed to define the prognostic value of genomic DNA methylation levels in stage III CM patients.

Methods

Overall level of genomic DNA methylation was measured using bisulfite pyrosequencing at three CpG sites (CpG1, CpG2, CpG3) of the Long Interspersed Nucleotide Element-1 (LINE-1) sequences in short-term CM cultures from 42 stage IIIC patients. The impact of LINE-1 methylation on overall survival (OS) was assessed using Cox regression and Kaplan-Meier analysis.

Results

Hypomethylation (i.e., methylation below median) at CpG2 and CpG3 sites significantly associated with improved prognosis of CM, CpG3 showing the strongest association. Patients with hypomethylated CpG3 had increased OS (P = 0.01, log-rank = 6.39) by Kaplan-Meyer analysis. Median OS of patients with hypomethylated or hypermethylated CpG3 were 31.9 and 11.5 months, respectively. The 5 year OS for patients with hypomethylated CpG3 was 48% compared to 7% for patients with hypermethylated sequences. Among the variables examined by Cox regression analysis, LINE-1 methylation at CpG2 and CpG3 was the only predictor of OS (Hazard Ratio = 2.63, for hypermethylated CpG3; 95% Confidence Interval: 1.21-5.69; P = 0.01).

Conclusion

LINE-1 methylation is identified as a molecular marker of prognosis for CM patients in stage IIIC. Evaluation of LINE-1 promises to represent a key tool for driving the most appropriate clinical management of stage III CM patients.

The biology of cancer testis antigens: putative function, regulation and therapeutic potential

Cancer testis antigens (CTA) are a large family of tumor-associated antigens expressed in human tumors of different histological origin, but not in normal tissues except for testis and placenta. This tumor-restricted pattern of expression, together with their strong in vivo immunogenicity, identified CTA as ideal targets for tumor-specific immunotherapeutic approaches, and prompted the development of several clinical trials of CTA-based vaccine therapy. Driven by this practical clinical interest, a more detailed characterization of CTA biology has been recently undertaken. So far, at least 70 families of CTA, globally accounting for about 140 members, have been identified. Most of these CTA are expressed during spermatogenesis, but their function is still largely unknown. Epigenetic events, particularly DNA methylation, appear to be the primary mechanism regulating CTA expression in both normal and transformed cells, as well as in cancer stem cells. In view of the growing interest in CTA biology, the aim of this review is to provide the most recent information on their expression, regulation and function, together with a brief summary of the major clinical trials involving CTA as therapeutic agents. The pharmacologic modulation of CTA expression profiles on neoplastic cells by DNA hypomethylating drugs will also be discussed as a feasible approach to design new combination therapies potentially able to improve the clinical efficacy of currently adopted CTA-based immunotherapeutic regimens in cancer patients.

Epigenetics of human cutaneous melanoma: setting the stage for new therapeutic strategies

Cutaneous melanoma is a very aggressive neoplasia of melanocytic origin with constantly growing incidence and mortality rates world-wide. Epigenetic modifications (i.e., alterations of genomic DNA methylation patterns, of post-translational modifications of histones, and of microRNA profiles) have been recently identified as playing an important role in melanoma development and progression by affecting key cellular pathways such as cell cycle regulation, cell signalling, differentiation, DNA repair, apoptosis, invasion and immune recognition. In this scenario, pharmacologic inhibition of DNA methyltransferases and/or of histone deacetylases were demonstrated to efficiently restore the expression of aberrantly-silenced genes, thus re-establishing pathway functions. In light of the pleiotropic activities of epigenetic drugs, their use alone or in combination therapies is being strongly suggested, and a particular clinical benefit might be expected from their synergistic activities with chemo-, radio-, and immuno-therapeutic approaches in melanoma patients. On this path, an important improvement would possibly derive from the development of new generation epigenetic drugs characterized by much reduced systemic toxicities, higher bioavailability, and more specific epigenetic effects.

Epigenetically regulated clonal heritability of CTA expression profiles in human melanoma

The intratumoral heterogeneity of cancer testis antigens (CTA) expression, which is driven by promoter methylation status, may hamper the effectiveness of CTA-directed vaccination of melanoma patients. Thus, we investigated whether the intratumoral heterogeneity of CTA expression is inherited at cellular level, or evolves throughout cellular replication, leading to a phenotypically unstable tumor cell population with reduced immunogenicity and/or able to escape immune control. Utilizing a previously characterized ex vivo clonal model of intratumoral heterogeneity of CTA expression in melanoma, Mel 313 MAGE-A3-low clone 5 (clone 5(M3-low)) and MAGE-A3-high clone 14 (clone 14(M3-high)) were sub-cloned and analyzed for CTA profile. Molecular assays demonstrated that levels of MAGE-A3 expression were highly conserved among generated sub-clones, as compared to parental clones. A similar behavior was identified for an extensive panel of other CTA investigated. Inherited levels of MAGE-A3 expression correlated with the extent of promoter methylation among clone 5(M3-low) and clone 14(M3-high) sub-clones analyzed. Treatment of clone 5(M3-low) with a DNA hypomethylating agent (DHA) resulted in an up-regulated expression of MAGE-A3, which was inherited at single cell level, being still detectable at day 60 in its sub-clones. Bisulfite sequencing demonstrated that also MAGE-A3 promoter methylation status was inherited among sub-clones generated from DHA-treated clone 5(M3-low) and strictly correlated with MAGE-A3 expression levels in investigated sub-clones. Similar results were obtained for additional CTA studied. Altogether our findings demonstrate that constitutive and DHA-modified CTA profiles of melanoma cells are clonally inherited throughout cellular replications, thus providing relevant insights to improve the effectiveness of CTA-based immunotherapy.

Cancer testis antigens in human melanoma stem cells: expression, distribution, and methylation status

Neoplastic populations with stem cell potential have been most recently identified in human cutaneous melanoma, and initially characterized for their phenotypic profile. Being melanoma stem cells (MSC) the most desirable target of therapeutic intervention, we asked whether they express the epigenetically-regulated cancer testis antigens (CTA) on which melanoma immunotherapy is increasingly focusing. Reverse transcription-PCR analyses identified the presence of the large majority of investigated CTA (i.e., MAGE, GAGE, NY-ESO, and SSX families) in different MSC populations. MSC expressed MAGE-A proteins as detected by western blot; noteworthy, the distribution of MAGE-A proteins was highly homogeneous within given MSC populations as shown by confocal immunofluorescence. Promoter methylation studies unveiled a homogeneously-demethylated MAGE-A3 promoter that paired MAGE-A3 expression in MSC. Altogether these findings demonstrate that MSC can be efficiently targeted by CTA-directed immunotherapeutic approaches, and suggest that epigenetic patterns most likely drive the expression of CTA in MSC as previously shown for melanoma cells.

Epigenetic drugs as pleiotropic agents in cancer treatment: biomolecular aspects and clinical applications

In the last three decades huge efforts have been made to characterize genetic defects responsible for cancer development and progression, leading to the comprehensive identification of distinct cellular pathways affected by the alteration of specific genes. Despite the undoubtable role of genetic mechanisms in triggering neoplastic cell transformation, epigenetic modifications (i.e., heritable changes of gene expression that do not derive from alterations of the nucleotide sequence of DNA) are rapidly emerging as frequent alterations that often occur in the early phases of tumorigenesis and that play an important role in tumor development and progression. Epigenetic alterations, such as modifications in DNA methylation patterns and post-translational modifications of histone tails, behave extremely different from genetic modifications, being readily revertable by "epigenetic drugs" such as inhibitors of DNA methyl transferases and inhibitors of histone deacetylases. Since epigenetic alterations in cancer cells affect virtually all cellular pathways that have been associated to tumorigenesis, it is not surprising that epigenetic drugs display pleiotropic activities, being able to concomitantly restore the defective expression of genes involved in cell cycle control, apoptosis, cell signaling, tumor cell invasion and metastasis, angiogenesis and immune recognition. Prompted by this emerging clinical relevance of epigenetic drugs, this review will focus on the large amount of available data, deriving both from in vitro experimentations and in vivo pre-clinical and clinical studies, which clearly indicate epigenetic drugs as effective modifiers of cancer phenotype and as positive regulators of tumor cell biology with a relevant therapeutic potential in cancer patients.

Functional Up-regulation of Human Leukocyte Antigen Class I Antigens Expression by 5-aza-2′-deoxycytidine in Cutaneous Melanoma: Immunotherapeutic Implications

PURPOSE

To investigate the potential of the DNA hypomethylating agent 5-aza-2'-deoxycytidine (5-aza-CdR) to improve the effectiveness of immunotherapeutic approaches against melanocyte differentiation antigens.

EXPERIMENTAL DESIGN

The effect of 5-aza-CdR on the constitutive expression of gp100 was investigated in 11 human melanoma cell lines by real-time reverse transcription-PCR and indirect immunofluorescence (IIF) analyses. 5-aza-CdR-mediated changes in the levels of expression of human leukocyte antigen (HLA) class I antigens and HLA-A2 allospecificity, intercellular adhesion molecule-1 (ICAM-1), and leukocyte-function-associated antigen-3 were investigated by IIF analysis on melanoma cells under study. The recognition of gp100-positive Mel 275 melanoma cells, treated or not with 5-aza-CdR, by HLA-A2-restricted gp100((209-217))-specific CTL was investigated by (51)Cr-release assays, IFN-gamma release and IFN-gamma ELISPOT assays.

RESULTS

The constitutive expression of gp100 was not affected by 5-aza-CdR on all melanoma cells investigated. Compared with untreated cells, the exposure of Mel 275 melanoma cells to 5-aza-CdR significantly (P < 0.05) up-regulated their expression of HLA class I antigens and of ICAM-1. These phenotypic changes significantly (P < 0.05) increased the lysis of 5-aza-CdR-treated Mel 275 melanoma cells by gp100-specific CTL and increased their IFN-gamma release. 5-aza-CdR treatment of Mel 275 cells also induced a higher number of gp100-specific CTL to secrete IFN-gamma.

CONCLUSIONS

Treatment with 5-aza-CdR improves the recognition of melanoma cells by gp100-specific CTL through the up-regulation of HLA class I antigens expression; ICAM-1 also contributes to this phenomenon. These findings highlight a broader range of therapeutic implications of 5-aza-CdR when used in association with active or adoptive immunotherapeutic approaches against a variety of melanoma-associated antigens.

Phenotypic and functional changes of human melanoma xenografts induced by DNA hypomethylation: immunotherapeutic implications

Emerging in vitro evidence points to an immunomodulatory activity of DNA hypomethylating drugs in human malignancies. We investigated the potential of 5-aza-2'-deoxycytidine (5-AZA-CdR) to modulate the expression of cancer testis antigens (CTA) and of HLA class I antigens by melanoma xenografts, and the resulting modifications in immunogenicity of neoplastic cells. Three primary cultures of melanoma cells, selected for immune phenotype and growth rate, were grafted into BALB/c nu/nu mice that were injected intraperitoneally with different dose- and time-schedules of 5-AZA-CdR. Molecular analyses demonstrated a de novo long-lasting expression of the CTA MAGE-1, -2, -3, -4, -10, GAGE 1-6, NY-ESO-1, and the upregulation of MAGE-1, MAGE-3, and NY-ESO-1 levels in melanoma xenografts from 5-AZA-CdR-treated mice. Serological and biochemical analyses identified a de novo expression of NY-ESO-1 protein and a concomitant and persistent upregulation of HLA class I antigens and of HLA-A1 and -A2 alleles. Immunization of BALB/c mice with 5-AZA-CdR-treated melanoma cells generated high titer circulating anti-NY-ESO-1 antibodies. Altogether, the data obtained identify an immunomodulatory activity of 5-AZA-CdR in vivo and strongly suggest for its clinical use to design novel strategies of CTA-based chemo-immunotherapy for melanoma patients.

Methylation-regulated expression of cancer testis antigens in primary effusion lymphoma: immunotherapeutic implications

Primary effusion lymphoma (PEL) is a large B-cell neoplasm with an unfavorable prognosis and limited therapeutic options. In this study, cancer testis antigens (CTA) were investigated as potential immunotherapeutic targets in patients with PEL. Baseline expression of a panel of 11 CTA was highly heterogeneous among five PEL cell lines. In particular, the investigated CTA were not expressed in BC-2 and BC-3 cells, while BC-1, HBL-6, and BCBL-1 cells tested positive for 6, 8, and 9 CTA, respectively. The DNA hypomethylating agent 5-aza-2'-deoxycytdine (5-AZA-CdR) invariably induced or up-regulated the expression of all investigated CTA in all cell lines analyzed. The de novo expression of CTA was still detectable at mRNA and protein level at least 2 months after the end of 5-AZA-CdR treatment. These findings, and the concomitant up-regulation of HLA-class I antigens and ICAM-1 by 5-AZA-CdR, support its clinical use to set-up innovative chemo-immunotherapeutic approaches in PEL.

Intratumor Heterogeneity of Cancer/Testis Antigens Expression in Human Cutaneous Melanoma Is Methylation-Regulated and Functionally Reverted by 5-Aza-2′-deoxycytidine

Cancer/testis antigens (CTA) are suitable targets for immunotherapy of human malignancies, and clinical trials are mainly focusing on MAGE-A3. However, the heterogeneous intratumor expression of CTA may hamper the effectiveness of CTA-directed vaccination through the emergence of CTA-negative neoplastic clones. We investigated the intratumor heterogeneity of CTA in human melanoma and the underlying molecular mechanism(s) at clonal level using 14 single cell clones generated from the melanoma lesion Mel 313. Reverse transcription-PCR revealed a highly heterogeneous expression of MAGE-A1, -A2, -A3, -A4, -A6, GAGE 1-6, SSX 1-5, and PRAME among melanoma clones. Only nine clones expressed MAGE-A3 and competitive reverse transcription-PCR identified relative differences in the number of mRNA molecules of up to 130-fold between clones 5 and 14. This clonal heterogeneity of MAGE-A3 expression correlated with the methylation status of specific CpG dinucleotides in MAGE-A3 promoter: i.e., hypomethylated CpG dinucleotides at positions -321, -151, -19, -16, -5, -2, +21, and +42 were found in clones expressing high but not low levels of MAGE-A3. Supporting the role of DNA methylation in generating the intratumor heterogeneity of CTA, the DNA hypomethylating agent 5-aza-2'-deoxycytidine (5-AZA-dCyd) invariably induced their expression in all CTA-negative clones. Furthermore, 5-AZA-dCyd-treatment reduced to 6 folds the differential expression of MAGE-A3 between clones 5 and 14, which became recognized to a similar extent by T cells specific for a MAGE-A-encoded peptide. These findings identify promoter methylation as directly responsible for the intratumoral heterogeneity of therapeutic CTA in melanoma and foresee the use of 5-AZA-dCyd to overcome the limitations set by their intratumor heterogeneous expression to CTA-based vaccine therapy.

Analysis of cancer/testis antigens in sporadic medullary thyroid carcinoma: expression and humoral response to NY-ESO-1

Cancer/testis antigens (CTA) are tumor-associated antigens expressed during ontogenesis, in a number of solid tumors but not in normal tissues except testis. Most of these CTA are highly immunogenic, eliciting a humoral and cellular response in the patients with advanced cancer, and are useful for tumor-specific immunotherapy. Medullary thyroid carcinoma (MTC) is a neoplasm derived from the parafollicular cells of the thyroid and occurs in either a sporadic or a familial form. In the present study, we examined by RT-PCR the expression of a number of genes encoding CTA in 23 surgical samples of sporadic MTC. Among the 11 cDNA antigens examined, RAGE, MAGE-4, and GAGE 1-2, were not expressed in any of the tissues. SSX 2 was present only in one tissue, whereas BAGE, GAGE 1-6, MAGE-1, MAGE-2, MAGE-3, and SSX 1-5 were detected in two to five samples. NY-ESO-1 cDNA was the most frequent, being detected in 15 of 23 examined samples (65.2%). Six (26.1%) tissues did not express any CTA-specific mRNA, whereas 10 tumors expressed only one gene (43.5%), 3 (21.4%) expressed 2 genes, and 4 displayed a broad CTA gene expression. NY-ESO-1 expression in primary MTC tissues significantly correlated with tumor recurrence. The presence of specific anti-NY-ESO-1 antibodies was searched in the sera of MTC-affected patients examined by ELISA using recombinant NY-ESO-1 protein. A humoral response against this CTA was detected in 6 of 11 NY-ESO-1 expressing patients (54.5%), and in 1 of 6 patients with NY-ESO-1-negative tumor. No anti-NY-ESO-1 antibodies were detected in healthy subjects (n = 17). The presence of anti-NY-ESO-1 antibodies was searched also in the sera of MTC affected patients whose tissues were not available for CTA analysis. Anti-NY-ESO-1 antibodies were present in 15 of 42 sera (35.7%), demonstrating that MTC is a neoplasm frequently associated with humoral immune response to NY-ESO-1. Serological survey may be useful as a way to identify patients with humoral immune response to NY-ESO-1 that provide a new attractive target for vaccine-based immunotherapy of MTC.

Differential levels of soluble endoglin (CD105) in myeloid malignancies

Angiogenesis contributes to disease progression in solid and hematopoietic malignancies, and endoglin (CD105), a component of the transforming growth factor (TGF)-beta receptor complex, is a powerful marker of neovascularization. Elevated amounts of soluble CD105 (sCD105) have been recently identified in selected solid tumors but no data are available on sCD105 in hematopoietic malignancies. Therefore, levels of sCD105 were investigated in sera of patients with acute myeloid leukemia (AML) (n = 10) or chronic myeloproliferative disorders (CMD) (n = 28), and correlated with those of soluble TGF-beta(1) (sTGF-beta(1)). Dot blot assay detected higher amounts of sCD105 (P < 0.05) both in AML (4.34 +/- 2.62 OD/mm(2)) and in CMD (3.71 +/- 2.09 OD/mm(2)) patients than in healthy subjects (n = 14, 2.38 +/- 1.18 OD/mm(2)). Instead, enzyme-linked immunosorbent assay (ELISA) identified (P < 0.05) lower and higher levels of sTGF-beta(1) in AML (32,017 +/- 1,900 pg/ml) and CMD (60,700 +/- 19,200 pg/ml) patients, respectively, compared to healthy individuals (n = 11, 47,173 +/- 5,443 pg/ml). In essential thrombocythemia (ET) patients with thrombotic episodes, levels of sCD105 were lower (P < 0.05) compared to patients without thrombotic complications, and inversely correlated with those of sTGF-beta(1) (r = 0.94). Conversely, amounts of sCD105 directly correlated with levels of sTGF-beta(1) (r = 0.74) in ET patients without thrombotic events. Our results show that high levels of sCD105 are present in myeloid malignancies that are characterized by a high cellular proliferation rate, and suggest that an altered balance between sCD105 and sTGF-beta(1) might favor disease progression and clinical complications.

5-aza-2'-deoxycytidine-induced expression of functional cancer testis antigens in human renal cell carcinoma: immunotherapeutic implications

PURPOSE

Limited therapeutic options are presently available for advanced renal cell carcinoma (RCC). This study was designed to define the clinical potential of the DNA hypomethylating agent 5-aza-2'-deoxycytidine (5-AZA-CdR) in human RCC, through its control of the expression of "therapeutic targets" of the cancer testis antigen (CTA) family, and of the tumor-associated antigen RAGE-1, in RCC cells.

EXPERIMENTAL DESIGN

Reverse transcription (RT)-PCR assays of a panel of RCC cells treated with 5-AZA-CdR, investigated the induction of the expression of several CTAs and of RAGE-1. Immunoprecipitation and Western blotting assessed whether the expression of CTA-specific mRNA induced by 5-AZA-CdR resulted in a translated protein of appropriate molecular weight. The functional activity of de novo expressed CTA was evaluated using (51)Cr release cytotoxicity assays of 5-AZA-CdR-treated HLA-A2-positive RCC cells using HLA-A2-restricted NY-ESO-1-specific CTLs.

RESULTS

Exposure to 5-AZA-CdR invariably induced the expression of the CTA MAGE-1, -2, -3, and -4, GAGE 1-6, and NY-ESO-1 in all of the RCC cells investigated. De novo expression of NY-ESO-1 was persistent, being still detectable 60 days after the end of treatment, and generated a functional protein efficiently recognized by HLA-A2-restricted NY-ESO-1-specific CTLs. 5-AZA-CdR also induced RAGE-1 expression in RAGE-1-negative RCC and sarcoma cells but not in neoplastic cells of different histology.

CONCLUSIONS

This study provides the scientific rationale to establish new strategies of chemoimmunotherapy in RCC patients. The well-defined immunogenicity of the investigated CTAs and of RAGE-1 suggest that systemic administration of 5-AZA-CdR represents a promising strategy to enhance the constitutively poor immunogenic potential of RCC cells, and to propose that virtually all RCC patients receive active and/or adoptive CTA- or RAGE-1-based immunotherapy.

Cancer testis antigens expression in mesothelioma: role of DNA methylation and bioimmunotherapeutic implications

Recent evidences suggest that malignant mesothelioma may be sensitive to immunotherapy; however, little is known about malignant mesothelioma-associated tumour antigens. Focusing on cancer/testis antigens, the expression of well-characterised immunogenic tumour-associated antigens was investigated in malignant mesothelioma cells. At variance with MAGE-4 and NY-ESO-1, malignant mesothelioma cells frequently expressed MAGE-1, -2 and -3, GAGE 1-2, GAGE 1-6, SSX-2 and SSX 1-5, and distinct malignant mesothelioma cells concomitantly expressed at least four cancer/testis antigens. Additionally, the tumour-associated antigens RAGE-1 was expressed at high levels in both benign and malignant mesothelial cells. Lastly, treatment with the DNA hypomethylating agent 5-aza-2'-deoxycytidine induced and up-regulated the expression of the cancer/testis antigen examined in malignant mesothelioma cells. Overall, these findings strongly suggest that cancer/testis antigens-based immunotherapy may represent a suitable therapeutic approach to malignant mesothelioma, and foresee the clinical use of 5-aza-2'-deoxycytidine to design new chemo-immunotherapeutic strategies in malignant mesothelioma patients.

Recombinant transmembrane CD59 (CD59-TM) confers complement resistance to GPI-anchored protein defective melanoma cells

Protectin (CD59) is a glycosylphosphatidylinositol (GPI)-anchored cell membrane glycoprotein, broadly expressed on melanocytic cells, that represents the main restriction factor of complement (C)-mediated lysis of human melanoma cells. Levels of CD59 expression may impair the clinical efficacy of C-activating monoclonal antibodies (mAb); thus, we investigated the molecular mechanisms underlying the lack of CD59 expression in selected melanoma cells. Serological and biochemical analyses showed that MeWo melanoma cells expressed CD59 neither at cell surface nor at cytoplasmic levels; however, no critical mutations were identified in their CD59 mRNA. Consistently, MeWo CD59 cDNA (MeWo-CD59) was appropriately translated when transfected into the CD59-positive Mel 100 melanoma cells, and into the CD59-negative Nalm-6 pre-B leukemia cells that acquired resistance to C. In contrast, transfection of MeWo cells with CD59 cDNA from Mel 275 melanoma cells did not induce CD59 expression; however, their transfection with the CD59-TM chimeric construct, obtained by replacing the GPI-anchoring signal of MeWo-CD59 with the transmembrane tail of the human low-density lipoprotein receptor, induced the expression of a C-protective transmembrane form of CD59. These data, together with the absent expression of additional GPI-anchored proteins (i.e., CD55), suggest that defects in the biosynthesis and/or processing of GPI-anchored proteins underlie the lack of CD59 expression in MeWo cells. Further unveiling of the molecular mechanism that turns off CD59 expression in human melanoma cells will help to set-up more effective therapeutic strategies utilizing C-activating mAb in melanoma patients.

Promoter methylation controls the expression of MAGE2, 3 and 4 genes in human cutaneous melanoma

Cancer-testis antigens expressed by different-histotype transformed cells are suitable targets for tumor immunotherapy. However, their heterogeneous expression in neoplastic lesions limits the eligibility of patients for cancer-testis antigen-directed vaccination, and low levels of cancer-testis antigens' expression may impair immune recognition of malignant cells. Because of the primary clinical relevance of cancer-testis antigens' expression in neoplastic tissues, 68 unrelated or sequential metastatic lesions from 56 patients were used to characterize the molecular mechanisms regulating the presence and levels of expression of different cancer-testis antigens of the MAGE family (i.e., MAGE2, 3 and 4) in cutaneous melanoma. Polymerase chain reaction-based methylation analyses showed that methylation status of specific cytosine-guanine dinucleotides in the promoters of investigated cancer-testis antigens correlated with their heterogeneous expression within unrelated metastatic melanoma lesions, and with their homogeneous expression among sequential metastases from three patients with melanoma. Unlike methylated promoters, unmethylated promoters of MAGE2, 3 and 4 genes drove the expression of reporter gene-enhanced green fluorescent protein after transient transfection of cancer-testis antigen-positive Mel 142 melanoma cells. Furthermore, de novo expression of MAGE3 gene induced by the treatment of Mel 195 melanoma cells with the DNA hypomethylating agent 5-aza-2'-deoxycytidine was associated with a 6%-12% demethylation of selected cytosine-guanine dinucleotides in its promoter. Finally, 5-aza-2'-deoxycytidine induced a 16-fold increase of MAGE3 expression in Mel 313 melanoma cells expressing constitutively low levels of the antigen, but did not affect that of Mel 275 melanoma cells expressing high baseline levels of MAGE3. Overall, these findings identify promoter methylation as a shared mechanism directly regulating the expression of therapeutic cancer-testis antigens in metastatic melanomas, and foresee the clinical use of 5-aza-2'-deoxycytidine to design new chemoimmunotherapeutic strategies in patients with melanoma.

Overexpression of protectin (CD59) down-modulates the susceptibility of human melanoma cells to homologous complement

The clinical efficacy of therapeutic complement (C)-activating monoclonal antibodies (mAb) to melanoma-associated antigens can be impaired by the levels of expression of C-inhibitory molecules on neoplastic cells. Protectin (CD59) is a glycosylphosphatidylinositol (GPI)-anchored cell membrane glycoprotein, acting as terminal regulator of C cascade, which is heterogeneously expressed in melanomas and represents the main restriction factor of C-mediated lysis of melanoma cells. Thus, we investigated whether the overexpression of CD59 could influence the constitutive susceptibility of distinct melanoma cells to homologous C. Infection of CD59-positive Mel 100 and 70-W melanoma cells by a retroviral vector carrying the CD59 cDNA, significantly (P < 0.05) upregulated their constitutive expression of CD59, whereas it did not affect that of additional C-regulatory molecules. Transduced CD59 was entirely GPI-anchored and showed a molecular weight identical to native CD59. Additionally, higher amounts of soluble CD59 were detected in the conditioned media of CD59-transduced melanoma cells compared with parental cells. CD59-transduced melanoma cells, sensitized by the anti-GD3 disialoganglioside mAb R24, were significantly (P < 0.05) less susceptible to homologous C-lysis than were parental cells; this effect was fully reverted by the masking of CD59 with F(ab')(2) fragments of the anti-CD59 mAb YTH53.1. These results provide conclusive evidence demonstrating that absolute levels of CD59 expression regulate the susceptibility to homologous C of specific melanoma cells, and suggest an additional explanation for the poor clinical results obtained with C-activating mAb in the clinical setting.

Melanoma cells constitutively release an anchor-positive soluble form of protectin (sCD59) that retains functional activities in homologous complement-mediated cytotoxicity

Protectin (CD59), a glycosylphosphatidylinositol-anchored cell membrane glycoprotein, is differentially expressed on melanocytic cells and represents the main restriction factor of C-mediated lysis of melanoma cells. In this study, we report that CD59-positive melanoma cells constitutively release a soluble form of CD59 (sCD59), and that its levels directly correlate (r = 0.926; P < 0.05) with the amount of membrane-bound CD59. SDS-PAGE analysis showed that the molecular components of sCD59 are similar to those of cellular CD59 expressed by melanoma cells. Melanoma-released sCD59 is anchor positive since it inserts into cell membranes of homologous cells that transiently increase their expression of CD59. Moreover, sCD59 is functional: it blocks the binding of the anti-CD59 mAb YTH53.1 to melanoma cells and reverses its effects on C-mediated lysis. In fact, preincubation of mAb YTH53.1 with scalar doses of conditioned media of CD59-positive but not of CD59-negative melanoma cells reduced significantly (P < 0.05), and in a dose-dependent fashion, the enhancement of C-mediated lysis of anti-GD3-sensitized melanoma cells induced by the masking of cellular CD59 by mAb YTH53.1. Altogether, these data demonstrate that CD59-positive human melanoma cells release a soluble form of CD59 that is structurally similar to cellular CD59, retains its anchoring ability, is functional, and may impair the effectiveness of clinical approaches to humoral immunotherapy for human melanoma.

Expression and structural features of endoglin (CD105), a transforming growth factor beta1 and beta3 binding protein, in human melanoma

Human endoglin (CD105) is a member of the transforming growth factor beta (TGF-beta) receptor family that binds TGF-beta1 and -beta3, but not TGF-beta2, on human endothelial cells. Immunohistochemical analyses demonstrated that CD105 is expressed on normal and neoplastic cells of the melanocytic lineage. The anti-CD105 MAb, MAEND3, stained 50, 25 and 34% of intradermal naevi, primary and metastatic melanomas investigated, respectively, and nine out of 12 melanoma cell lines. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis revealed that CD105 expressed by melanoma cells consists of a homodimeric protein with an apparent molecular weight of 180 and 95 kDa under non-reducing and reducing conditions. Cross-linking of 125I-labelled TGF-beta1 to melanoma cells, Mel 97, by disuccinimidyl suberate (DSS) demonstrated that CD105 expressed on pigmented cells binds TGF-beta1; the pattern of binding of TGF-beta1 to melanoma cells was found to be similar to that of human umbilical vein endothelial cells. The addition of exogenous, bioactive TGF-beta1 significantly (P<0.05) inhibited the growth of CD105-positive melanoma cells, Mel 97, but did not affect that of CD105-negative melanoma cells, F0-1. These data, altogether, demonstrate that CD105 is expressed on pigmented cells and might play a functionally relevant role in the biology of human melanoma cells by regulating their sensitivity to TGF-betas.

Levels of cell membrane CD59 regulate the extent of complement-mediated lysis of human melanoma cells

Normal and neoplastic cells are protected from autologous complement (C) attack by different cell-surface C-regulatory proteins including CD59 (protectin), CD46 (membrane cofactor protein) and CD55 (decay-accelerating factor). Indirect immunofluorescence (IIF) analysis showed a differential expression of CD59, CD46, and CD55 in nine human melanoma cell lines and that the expression of CD59 was highly heterogeneous compared with that of CD46 and CD55. Levels of cell membrane CD59 were found to regulate the differential sensitivity of melanoma cells investigated to homologous C-mediated lysis; in fact, an inverse correlation (r > 0.7, p < 0.05) was found between levels of cell membrane CD59, but not of CD46 and CD55, and extent of C-mediated lysis of melanoma cells sensitized with scalar concentrations of the anti-GD3 ganglioside mAb R24. Masking of CD59 by 2.5 micrograms/ml of the anti-CD59 mAb YTH53.1 induced or enhanced C-mediated lysis of melanoma cells sensitized with 2.5 micrograms/ml of mAb R24; the latter phenomenon was found to be directly correlated (r > 0.865, p < 0.01) with levels of cell membrane CD59. CD59 is bound to melanoma cells by a glycosylphosphatidylinositol anchor: treatment of C-resistant melanoma cells Mel 97, by increasing doses of phosphatidylinositol-specific phospholipase C (PI-PLC), progressively decreased cell-surface expression of CD59 and increased C-mediated lysis of cells sensitized with mAb R24. Staining of 38 benign and malignant lesions of melanocytic origin by mAb YTH53.1 demonstrated that CD59 is consistently expressed in vivo and confirmed the heterogeneous expression detected in vitro. Our data, altogether, demonstrate that CD59 is the main restriction factor of C-mediated lysis of melanoma cells and that levels of CD59 may account for their differential resistance to C-mediated lysis. The analysis of the levels of CD59 could represent an useful strategy in selecting melanoma patients who may benefit from immunotherapeutic treatment(s) that trigger C activation.

Type VI collagen: high yields of a molecule with multiple forms of alpha 3 chain from avian and human tissues

A differential extraction procedure followed by molecular sieve column chromatography for the isolation of large quantities of the tissue form of type VI collagen is described. Recovery of the protein was more than 60% from both chick gizzard and human placenta. On reduced NaDodSO4-gels chick type VI collagen migrated as two major bands at Mr = 140,000 and 150,000 that were present in a 1:1 ratio and five less intense bands between Mr = 230,000 and 180,000. By immunoblotting with a polyclonal antibody against the pepsinized form of chick type VI collagen, all these bands were stained. Furthermore, the amino acid composition of the five higher Mr polypeptides indicated that they all contained hydroxyproline and hydroxylysine. In the chick type VI collagen molecule the five bands of higher Mr belong to the alpha 3 chain since they were recognized by monoclonal antibodies specific for the chick Mr = 260,000 alpha 3 chain. On examination of antigenic activity by solid-phase radioimmunobinding, densitometry of stained NaDodSO4 polyacrylamide gels, and protein content type VI was found to be an abundant collagen since it accounted for up to 0.1% of the tissue wet weight. The yields per tissue wet weight and the migration pattern of human type VI collagen polypeptides were similar to those of the chick. Agarose/polyacrylamide composite gels indicated that the molecular size of the tissue form of type VI collagen molecules under non-reduced conditions corresponded to a basic type of tetrameric molecule.