Loss of Heterozygosity of 9p Is Associated with Poorer Survival in Patients with Gliomas

A Synopsis of Biomarkers in Glioblastoma: Past and Present

Accounting for 48% of malignant brain tumors in adults, glioblastoma has been of great interest in the last decades, especially in the biomolecular and neurosurgical fields, due to its incurable nature and notable neurological morbidity. The major advancements in neurosurgical technologies have positively influenced the extent of safe tumoral resection, while the latest progress in the biomolecular field of GBM has uncovered new potential therapeutical targets. Although GBM currently has no curative therapy, recent progress has been made in the management of this disease, both from surgical and molecular perspectives. The main current therapeutic approach is multimodal and consists of neurosurgical intervention, radiotherapy, and chemotherapy, mostly with temozolomide. Although most patients will develop treatment resistance and tumor recurrence after surgical removal, biomolecular advancements regarding GBM have contributed to a better understanding of this pathology and its therapeutic management. Over the past few decades, specific biomarkers have been discovered that have helped predict prognosis and treatment responses and contributed to improvements in survival rates.

Targeting Loss of Heterozygosity: A Novel Paradigm for Cancer Therapy

Loss of heterozygosity (LOH) is a common genetic event in the development of cancer. In certain tumor types, LOH can affect more than 20% of the genome, entailing loss of allelic variation in thousands of genes. This reduction of heterozygosity creates genetic differences between tumor and normal cells, providing opportunities for development of novel cancer therapies. Here, we review and summarize (1) mutations associated with LOH on chromosomes which have been shown to be promising biomarkers of cancer risk or the prediction of clinical outcomes in certain types of tumors; (2) loci undergoing LOH that can be targeted for development of novel anticancer drugs as well as (3) LOH in tumors provides up-and-coming possibilities to understand the underlying mechanisms of cancer evolution and to discover novel cancer vulnerabilities which are worth a further investigation in the near future.

Loss of 5'-Methylthioadenosine Phosphorylase (MTAP) is Frequent in High-Grade Gliomas; Nevertheless, it is Not Associated with Higher Tumor Aggressiveness

The 5’-methylthioadenosine phosphorylase (MTAP) gene is located in the chromosomal region 9p21. MTAP deletion is a frequent event in a wide variety of human cancers; however, its biological role in tumorigenesis remains unclear. The purpose of this study was to characterize the MTAP expression profile in a series of gliomas and to associate it with patients’ clinicopathological features. Moreover, we sought to evaluate, through glioma gene-edited cell lines, the biological impact of MTAP in gliomas. MTAP expression was evaluated in 507 glioma patients by immunohistochemistry (IHC), and the expression levels were associated with patients’ clinicopathological features. Furthermore, an in silico study was undertaken using genomic databases totalizing 350 samples. In glioma cell lines, MTAP was edited, and following MTAP overexpression and knockout (KO), a transcriptome analysis was performed by NanoString Pan-Cancer Pathways panel. Moreover, MTAP’s role in glioma cell proliferation, migration, and invasion was evaluated. Homozygous deletion of 9p21 locus was associated with a reduction of MTAP mRNA expression in the TCGA (The Cancer Genome Atlas) - glioblastoma dataset (p < 0.01). In addition, the loss of MTAP expression was markedly high in high-grade gliomas (46.6% of cases) determined by IHC and Western blotting (40% of evaluated cell lines). Reduced MTAP expression was associated with a better prognostic in the adult glioblastoma dataset (p < 0.001). Nine genes associated with five pathways were differentially expressed in MTAP-knockout (KO) cells, with six upregulated and three downregulated in MTAP. Analysis of cell proliferation, migration, and invasion did not show any significant differences between MTAP gene-edited and control cells. Our results integrating data from patients as well as in silico and in vitro models provide evidence towards the lack of strong biological importance of MTAP in gliomas. Despite the frequent loss of MTAP, it seems not to have a clinical impact in survival and does not act as a canonic tumor suppressor gene in gliomas.

Prognostic impact of family history of cancer in Southern Chinese patients with esophageal squamous cell cancer

Background: First degree family history of cancer is associated with developing esophageal cancer and sparse data is about the impact on poor survival among established esophageal squamous cell cancer (ESCC) patients. In this study, we investigated the prognoses of patients with ESCC with a family history.

Methods: A total of 479 ESCC patients were retrospectively enrolled from a Southern Chinese institution. A positive family history was defined as having malignant cancer among parents and siblings. Kaplan-Meier plots and Cox proportional hazards regressions were applied for overall survival (OS) and progression-free survival (PFS).

Results: Among 479 patients, 119 (24.8%) and 68 (14.2%) reported a first-degree family history of cancer and digestive tract cancer, respectively. Compared with patients without a family history of cancer, the adjusted hazard ratios (HR) among those with it were 1.40 (95% CI, 1.08-1.82, p=0.011) for death, 1.36 (95% CI, 1.05-1.76, p=0.018) for progression. Similar results were observed in those with a family history of digestive tract cancer (HR=1.69, 95%CI, 1.24-1.98, p=0.001 for death and HR=1.77, 95%CI, 1.30-2.37, p<0.001 for progression, respectively). Furthermore, there was a trend for increasing risk of overall mortality (p=0.021, p=0.004, respectively), and progression (p=0.022, p=0.001, respectively) with an increasing number of affected family members.

Conclusion: A first-degree family history of cancer, especially digestive tract cancer is associated with poor survival for established ESCC patients and plays an important role in prognosis. The patients with a family history of cancer might need a greater intensity of treatment and more frequent follow-up.

Prognostic relevance of mutations and copy number alterations assessed with targeted next generation sequencing in IDH mutant grade II glioma

Background

At current prognostication of low grade glioma remains suboptimal and might be improved with additional markers. These may guide treatment decisions, in particular on early adjuvant therapy versus wait and see after surgery.

Methods

We used a targeted Next-Generation Sequencing panel to assess mutational and copy number status of selected genes and chromosomes in a consecutive series of adult grade II supratentorial glioma, and assessed the impact of molecular markers of interest on overall survival.

Results

207 IDH mutated grade II glioma samples were analyzed with a median follow-up of 6.9 years. Loss of region 9p21.3 did not show a correlation with outcome in IDH mutated 1p/19q-codeleted oligodendroglioma or IDH mutated astrocytoma. We found a significant shorter overall survival with univariable analysis in IDH mutated astrocytoma patients with trisomy of chromosome 7 (Log rank P = 0.044) and in IDH mutated 1p/19q-codeleted oligodendroglioma patients with a PTEN mutation (Log rank P = 0.033). We could not validate these findings in multivariate analysis or in the TCGA dataset.

Conclusions

Loss of 9p21.3 is not associated with outcome in a molecularly defined cohort of grade II glioma and therefore it remains unclear if loss of 9p21.3 can be used as additional marker of anaplasia or to guide treatment decisions. Trisomy of chromosome 7 in IDH mutated astrocytoma and PTEN mutations in IDH mutated oligodendroglioma are potential markers of poor prognosis, but require confirmation in larger series.

Electronic supplementary material

The online version of this article (10.1007/s11060-018-2867-8) contains supplementary material, which is available to authorized users.