Telomere profiles and tumor-associated macrophages with different immune signatures affect prognosis in glioblastoma

Abstract

Telomere maintenance is a hallmark of cancer and likely to be targeted in future treatments. In glioblastoma established methods of identifying telomerase and alternative lengthening of telomeres leave a significant proportion of tumors with no defined telomere maintenance mechanism. This study investigated the composition of these tumors using RNA-Seq. Glioblastomas with an indeterminate telomere maintenance mechanism had an increased immune signature compared with alternative lengthening of telomeres and telomerase-positive tumors. Immunohistochemistry for CD163 confirmed that the majority (80%) of tumors with an indeterminate telomere maintenance mechanism had a high presence of tumor-associated macrophages. The RNA-Seq and immunostaining data separated tumors with no defined telomere maintenance mechanism into three subgroups: alternative lengthening of telomeres like tumors with a high presence of tumor-associated macrophages and telomerase like tumors with a high presence of tumor-associated macrophages. The third subgroup had no increase in tumor-associated macrophages and may represent a distinct category. The presence of tumorassociated macrophages conferred a worse prognosis with reduced patient survival times (alternative lengthening of telomeres with and without macrophages P = 0.0004, and telomerase with and without macrophages P = 0.013). The immune signatures obtained from RNA-Seq were significantly different between telomere maintenance mechanisms. Alternative lengthening of telomeres like tumors with macrophages had increased expression of interferon-induced proteins with tetratricopeptide repeats (IFIT1-3). Telomerase-positive tumors with macrophages had increased expression of macrophage receptor with collagenous structure (MARCO), CXCL12 and sushi-repeat containing protein x-linked 2 (SRPX2). Telomerase-positive tumors with macrophages were also associated with a reduced frequency of total/near total resections (44% vs 476% for all other subtypes, P = 0.014). In summary, different immune signatures are found among telomere maintenance mechanism-based subgroups in glioblastoma. The reduced extent of surgical resection of telomerase-positive tumors with macrophages suggests that some tumor-associated macrophages are more unfavorable.

MR Imaging Characteristics Associate with Tumor-Associated Macrophages in Glioblastoma and Provide an Improved Signature for Survival Prognostication

“…3,4,29 There were no significant differences (P Ͼ .05) among telomere maintenance-based subgroups in relation to the amount of patients treated with radiation therapy, concurrent temozolomide, or adjuvant temozolomide. In an earlier study and in this study (Table 4), the ALTϪ/Mϩ subgroup was associated with an increased frequency of partial resections compared with near-total resections.…”

“…The CD163 antibody used was EPR19518 (Abcam, Cambridge, United Kingdom), and the macrophage content was estimated as described previously. 4 …”

“…4,25 Tumors from 80 cases were typed for telomere maintenance mechanisms as part of an earlier study, and 100 tumors were new to this study. 4 The tumor-associated macrophage content was identified by immunohistochemistry staining for CD163 positive macrophages. The CD163 antibody used was EPR19518 (Abcam, Cambridge, United Kingdom), and the macrophage content was estimated as described previously.…”

“…3 It has been recently found that most tumors without a defined telomere maintenance mechanism contain a high con-tent of tumor-associated macrophages (Mϩ) that affects assays assigning telomere maintenance. 4 The revised subgroups were ALT positive tumors with and without (MϪ) a high content of macrophages (ALTϩ/Mϩ and ALTϩ/MϪ) and ALT negative tumors with and without a high content of macrophages (ALTϪ/Mϩ and ALTϪ/MϪ). With temozolomide treatment, patients with ALTϪ/MϪ tumors have improved survival compared with patients with ALTϪ/Mϩ tumors, 4 suggesting that identifying the increased macrophage content will distinguish those with a poor outcome.…”

“…4 The revised subgroups were ALT positive tumors with and without (MϪ) a high content of macrophages (ALTϩ/Mϩ and ALTϩ/MϪ) and ALT negative tumors with and without a high content of macrophages (ALTϪ/Mϩ and ALTϪ/MϪ). With temozolomide treatment, patients with ALTϪ/MϪ tumors have improved survival compared with patients with ALTϪ/Mϩ tumors, 4 suggesting that identifying the increased macrophage content will distinguish those with a poor outcome. MR imaging is a diagnostic tool that evaluates tumor as well as peritumoral characteristics.…”