The Epigenetic Therapies Azacitidine and Sodium Valproate Augment Immune Responses to the MAGE Cancer Testis Antigen in Acute Myeloid Leukemia and Myeloma.

Abstract 2086

Poster Board II-63

The mechanism by which epigenetic therapies exert an anti-tumor effect in Acute Myeloid Leukemia (AML) and myeloma is unknown. We have studied immune responses to cancer testis antigens (CTA) a family of immunodominant tumor-associated antigens, in 12 patients with AML treated with the DNA methyltransferase inhibitor 5-Azacitidine (AZA) and the histone deacetylase inhibitor sodium valproate (VPA). The frequency of CTA-specific CD8+ T cells was studied in 12 patients with high risk AML prior to treatment with AZA (75 mg/m² × 7 days per 28 day cycle) and sodium valproate (1-2.5 g daily administered continuously as tolerated) on a Phase II clinical trial. CTA specific CTLs were detectable in 4 of 12 patients with relapsed AML undergoing treatment with AZA and VPA. In one patient CTLs specific to the peptide MAGE-A2_157-166 were detectable prior to commencement of trial therapy at a frequency of 0.001%.and persisted throughout treatment. In three patients CTLs were only detectable after commencement of AZA therapy. A polyclonal T cell line was subsequently generated from one patient and tetramer staining of the line revealed the presence of 1% MAGE-A2_157-166-specific T cells and this could be enriched using anti-PE magnetic beads (Miltenyi Biotec). Two patients in whom AZA induced a CTL response to MAGE achieved a partial response to trial therapy by Cheson criteria. Treatment with AZA resulted in up to 100fold increased levels of expression of MAGEA4, MAGEA1, HAGE, SSX1, NY ESO1, MAGEC1, LAGE and XAGE mRNA in AML cell lines: HL60, KG1a, U937 and NB4 and multiple myeloma cell lines: U266 and JJN3. We next studied whether prior treatment with AZA augmented recognition of hematopoietic tumors by MAGE specific T cell clones. Prior treatment with AZA increased recognition of two myeloma cell lines (JJN3 and U266) by a MAGEA1 specific T cell clone. This is the first demonstration that AZA induce a CTL response to MAGE in patients with AML. Taken together our data are consistent with the possibility that epigenetic manipulation of cancer testis antigen expression and induction of a tumor specific CTL response may contribute to the clinical activity of AZA in hematologic malignancies.