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

Our plain-English summary of Immunomodulatory activity of SGI-110, a 5-aza-2'-deoxycytidine-containing demethylating dinucleotide, by S. Coral, G. Parisi, H.J. Nicolay, et al (Cancer Immunology, Immunotherapy, 2013).

The study

• Authors: S. Coral, G. Parisi, H.J. Nicolay, F. Colizzi, R. Danielli, E. Fratta, A. Covre, P. Taverna, L. Sigalotti, M. Maio
• Journal: Cancer Immunology, Immunotherapy
• Published: 2013;62(3):605-14
• Cited by: 63 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

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.

In plain English

This laboratory study tested an experimental drug, SGI-110, on human cancer cell lines grown in culture; it did not study asbestos or patients. The lines included melanoma, sarcoma, renal cell carcinoma and two mesothelioma lines obtained from pleural effusions of mesothelioma patients. SGI-110 releases the drug 5-aza-2'-deoxycytidine (5-AZA-CdR), which removes methyl tags from DNA. After treatment, cells started making, or made more of, cancer/testis antigens, proteins the immune system can target. Results resembled those with 5-AZA-CdR, and in Mel 275 melanoma cells NY-ESO-1 mRNA remained detectable 80 days after treatment ended. A related compound that cannot release 5-AZA-CdR did not change the antigen, HLA class I or ICAM-1 levels measured. In melanoma cells SGI-110 raised levels of HLA class I and ICAM-1, surface molecules involved in immune recognition. HLA-A2-restricted, gp100-specific cytotoxic T cells killed treated Mel 275 melanoma cells more than untreated ones at an effector-to-target ratio of 25 to 1 (p less than 0.05); at lower ratios the difference was not statistically significant. The authors concluded SGI-110 is an attractive agent to increase immune recognition of cancer cells.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: in vitro laboratory experiment on human cancer cell lines (no patients, no animals)
• Who was studied: Human cancer cell lines. Melanoma: Mel 275, Mel 313, Mel 611, Mel 684, Mel 195, Mel 531. Sarcoma: MG-63 osteosarcoma, SK-LMS-1 leiomyosarcoma. Renal cell carcinoma: MZ-1257, LE-9104. Mesothelioma: MES-1, MPP-89, obtained from pleural effusion of mesothelioma patients.
• Exposure: The drug SGI-110 at 1 µM or 10 µM, given every 12 h for 2 days (4 pulses). It was compared with 1 µM 5-AZA-CdR, with a related compound (3'-3'-DpG) that cannot deliver 5-AZA-CdR, and with untreated controls. Asbestos exposure was not studied.
• Main results:
  • SGI-110 induced expression of cancer/testis antigens (MAGE-A1, -A2, -A3, -A4, -A10, GAGE 1-2, GAGE 1-6, NY-ESO-1, SSX 1-5) in the cancer cell lines tested. Per the table, not every antigen was induced in every line.
  • Quantitative tests showed MAGE-A3 and NY-ESO-1 mRNA induced or up-regulated in one representative line of each tumor type, including the mesothelioma line MPP-89.
  • The pattern of antigen induction was not different from that with an equal concentration of 5-AZA-CdR. 10 µM gave a similar pattern to 1 µM.
  • The related compound 3'-3'-DpG, which cannot deliver 5-AZA-CdR, did not change measured antigen expression in any of the cells. It also did not modulate HLA class I, HLA-A2 or ICAM-1.
  • In Mel 275 melanoma cells, measured by quantitative RT-PCR, NY-ESO-1 and MAGE-A1 mRNA induced by SGI-110 decreased over time. It was still detectable 80 days after the end of treatment.
  • In Mel 275 melanoma cells (three experiments, p less than 0.05), mean fluorescence intensity rose from 84.7 to 214.3 for HLA class I, from 20.3 to 43.7 for HLA-A2, and from 216 to 327 for ICAM-1 (untreated vs SGI-110 1 µM).
  • SGI-110 reduced promoter methylation of MAGE-A1 and NY-ESO-1. Mean demethylation was 57% and 30% in Mel 195 melanoma cells, and 22% and 33% in MZ-1257 renal cell carcinoma cells.
  • HLA-A2-restricted, gp100-specific cytotoxic T cells lysed SGI-110-treated Mel 275 melanoma cells significantly more (p less than 0.05) than untreated cells at an effector/target ratio of 25/1. At lower ratios the difference was not statistically significant.
  • The increased killing of treated Mel 275 cells was suppressed by antibodies blocking HLA class I or ICAM-1.
• The authors' conclusion: The authors concluded that SGI-110 is an attractive therapeutic agent to increase immunogenicity and immune recognition of cancer cells. In their view, this provides a rationale for clinical development in cancer immunotherapy.
• Limitations the authors state:
  • The authors stated that the low killing activity of the T-cell preparation did not allow a statistically significant difference to be shown at lower effector/target ratios.

Topics

Medical terms in this study, explained in our Lexicon: Immunotherapy, Mesothelioma, Carcinoma, Sarcoma, LDH Release.

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