Presenting Author:

Kristen Lauing, Ph.D.

Principal Investigator:

Derek Wainwright

Department:

Neurological Surgery

Keywords:

High grade glioma, pediatric, IDO1, inhibitors, diffuse pontine intrinsic glioma, therapeutics, brain cancer

Location:

Third Floor, Feinberg Pavilion, Northwestern Memorial Hospital

B98 - Basic Science

Characterizing IDO1 in human pediatric brain cancer

Indoleamine 2,3 dioxygenase 1 (IDO1) and tryptophan dioxygenase (TDO2) are tryptophan catabolic enzymes that have been implicated in facilitating immunosuppression in cancer. With respect to the central nervous system, both enzymes have been correlated with decreased overall survival in adult patients with glioma. Based on these observations, we questioned whether pediatric CNS tumors, which are the most common form of solid cancer in children, also possess expression and activity for these immunosuppressive mediators. To achieve this, purified RNA from pediatric patient tumor tissue was obtained from the Children’s Brain Tumor Tissue Consortium (Philadelphia, PA) and utilized for qRT-PCR analysis of IDO1, TDO2, CD3e, IFNγ, and TGFβ1. Primary cell lines were propagated from fresh tumor tissue acquired by Dr. Rintaro Hashizume, Ph.D. (Northwestern University) and cultured for 2,4,8,24, or 48 hours alone or with a combination of 100 ng/mL IFNγ and 250 nM 1-LMT, 1-DMT and BGB-5777; a novel pharmaceutical-grade IDO1 inhibitor (Beigene). Cell culture supernatants were collected at each time point for IDO1 protein expression analysis, IDO1 and TDO2 mRNA analysis, and for detection of tryptophan (Trp) and kynurenine (Kyn) levels by high pressure liquid chromatography. Results: qRT-PCR defined two populations of pediatric high grade glioma (HGG) based on high (>3 fold expression compared to control) versus low (<3 fold expression) IDO1 expression in patient tumor tissue. In contrast, low grade glioma (LGG) and diffuse intrinsic pontine glioma (DIPG) universally expressed low IDO1 levels when compared to HGG. All patient tumors expressed TDO2 mRNA. All tumors were infiltrated by T cells, based on the ubiquitous presence of CD3ε mRNA. Primary human pediatric cell lines (HGG and DIPG) inducibly expressed increased IDO1 protein and mRNA as early as 8 hours post-treatment with IFNγ (P < 0.001). To determine whether IDO1 was functionally active, BGB-5777, in addition to historical IDO1 pathway modulators, 1-LMT and 1-DMT, were co-incubated with the pediatric cell lines plus IFNγ. At 250 nM, BGB-5777 significantly decreased the Kyn/Trp ratio in both HGG and DIPG cell lines (p<0.001), while treatment with 1-LMT and 1-DMT concentrations had no impact. Treatment with BGB-5777 also induced a significant increase in IDO1 protein levels in HGG and DIPG cell lines at 24 and 48 hours post-treatment. Conclusion: These data show for the first time that IDO1 is expressed in pediatric tumors and the novel blood brain barrier-penetrating IDO1 inhibitor, BGB-5777, is a highly potent inhibitor of enzymatic activity in this setting. BGB-5777 appears to induce a stabilization effect of IFNγ-induced protein expression in glioma and DIPG cell lines. Given that IDO1 inhibitors are already in multiple clinical trials for adults with brain cancer, these data suggest that BGB-5777 may be a valuable tool for inhibiting IDO1 in the setting of malignant pediatric brain cancer.