Clinical Neuropathology Practice News 4-2012: levels of evidence for brain tumor biomarkers

Cysteine cathepsin C: a novel potential biomarker for the diagnosis and prognosis of glioma

Background

Cysteine cathepsin C encoded by the CTSC gene is an important member of the cysteine cathepsin family that plays a key role regulation of many types of tumors. However, whether CTSC is involved in the pathological process of glioma has not yet been reported. We comprehensively analyzed data from multiple databases and for the first time revealed a role and specific mechanism of action of CTSC in glioma, identifying it as a novel and efficient biomarker for the diagnosis and treatment of this brain tumor.

Methods

The expression of CTSC in glioma and its relationship with clinical characteristics and prognosis of patients with glioma were analyzed at different levels by using clinical sample information from several databases. CTSC expression levels in glioma and normal brain tissues, as well as in glioma cells and normal brain cells, was validated by real-time quantitative polymerase chain reaction (RT-qPCR). Gene set enrichment analysis (GSEA) was used to reveal the signaling pathways that CTSC may participate in. The connectivity map was used to reveal small molecules that may inhibit CTSC expression in glioma, and the putative effect of these compounds was verified by RT-qPCR.

Results

Our analyses showed that the expression of CTSC in glioma was higher than that in non-cancerous cells. GSEA showed that CTSC expression may regulate the malignant development of glioma through Toll-like receptor signaling pathways, pathways in cancer, and extracellular matrix receptor interaction signaling pathways. And we proved piperlongumine and scopoletin could inhibit CTSC expression in glioma cells.

Conclusions

CTSC may serve as an efficient molecular target for the diagnosis and therapy of glioma, thereby improving the poor prognosis of patients with glioma.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02417-6.

Analysis of Chemopredictive Assay for Targeting Cancer Stem Cells in Glioblastoma Patients

INTRODUCTION

The prognosis of glioblastoma (GBM) treated with standard-of-care maximal surgical resection and concurrent adjuvant temozolomide (TMZ)/radiotherapy remains very poor (less than 15 months). GBMs have been found to contain a small population of cancer stem cells (CSCs) that contribute to tumor propagation, maintenance, and treatment resistance. The highly invasive nature of high-grade gliomas and their inherent resistance to therapy lead to very high rates of recurrence. For these reasons, not all patients with similar diagnoses respond to the same chemotherapy, schedule, or dose. Administration of ineffective anticancer therapy is not only costly but more importantly burdens the patient with unnecessary toxicity and selects for the development of resistant cancer cell clones. We have developed a drug response assay (ChemoID) that identifies the most effective chemotherapy against CSCs and bulk of tumor cells from of a panel of potential treatments, offering great promise for individualized cancer management. Providing the treating physician with drug response information on a panel of approved drugs will aid in personalized therapy selections of the most effective chemotherapy for individual patients, thereby improving outcomes. A prospective study was conducted evaluating the use of the ChemoID drug response assay in GBM patients treated with standard of care.

METHODS

Forty-one GBM patients (mean age 54 years, 59% male), all eligible for a surgical biopsy, were enrolled in an Institutional Review Board-approved protocol, and fresh tissue samples were collected for drug sensitivity testing. Patients were all treated with standard-of-care TMZ plus radiation with or without maximal surgery, depending on the status of the disease. Patients were prospectively monitored for tumor response, time to recurrence, progression-free survival (PFS), and overall survival (OS). Odds ratio (OR) associations of 12-month recurrence, PFS, and OS outcomes were estimated for CSC, bulk tumor, and combined assay responses for the standard-of-care TMZ treatment; sensitivities/specificities, areas under the curve (AUCs), and risk reclassification components were examined.

RESULTS

Median follow-up was 8 months (range 3-49 months). For every 5% increase in in vitro CSC cell kill by TMZ, 12-month patient response (nonrecurrence of cancer) increased two-fold, OR=2.2 (P=.016). Similar but somewhat less supported associations with the bulk tumor test were seen, OR=2.75 (P=.07) for each 5% bulk tumor cell kill by TMZ. Combining CSC and bulk tumor assay results in a single model yielded a statistically supported CSC association, OR=2.36 (P=.036), but a much attenuated remaining bulk tumor association, OR=1.46 (P=.472). AUCs and [sensitivity/specificity] at optimal outpoints (>40% CSC cell kill and >55% bulk tumor cell kill) were AUC=0.989 [sensitivity=100/specificity=97], 0.972 [100/89], and 0.989 [100/97] for the CSC only, bulk tumor only, and combined models, respectively. Risk categorization of patients was improved by 11% when using the CSC test in conjunction with the bulk test (risk reclassification nonevent net reclassification improvement [NRI] and overall NRI=0.111, P=.030). Median recurrence time was 20 months for patients with a positive (>40% cell kill) CSC test versus only 3 months for those with a negative CSC test, whereas median recurrence time was 13 months versus 4 months for patients with a positive (>55% cell kill) bulk test versus negative. Similar favorable results for the CSC test were observed for PFS and OS outcomes. Panel results across 14 potential other treatments indicated that 34/41 (83%) potentially more optimal alternative therapies may have been chosen using CSC results, whereas 27/41 (66%) alternative therapies may have been chosen using bulk tumor results.

CONCLUSIONS

The ChemoID CSC drug response assay has the potential to increase the accuracy of bulk tumor assays to help guide individualized chemotherapy choices. GBM cancer recurrence may occur quickly if the CSC test has a low in vitro cell kill rate even if the bulk tumor test cell kill rate is high.

KINFix--A formalin-free non-commercial fixative optimized for histological, immunohistochemical and molecular analyses of neurosurgical tissue specimens

An optimal fixative should ideally combine the advantages of formalin fixation and freezing, allowing for good preservation of histology and molecular components, easy handling and storage, lack of toxicity, and low costs. Most of these criteria are fulfilled by ethanol-based solutions, and due to our good experience with the commercial RCL2 fixative, reflected by our published single-center trial, we initiated a multicenter ring trial. However, during its course, RCL2 was discontinued on the market. Therefore, we created our own agent, KINFix, composed of the same main constituents as RCL2, and employed it in our laboratory with similar results. Here we present our evaluation of the three fixatives formalin, RCL2, and KINFix from the perspective of histopathology as well as nucleic acid and protein analyses in comparison to fresh frozen tissues together with the multicenter ring trial data for RCL2. We observe that RCL2 and KINFix offer comparable histomorphology and superior template for molecular analyses than formalin. Moreover, KINFix as freely available fixative might overcome some of the difficulties related to the commercial agents. Therefore, we conclude that KINFix might be an attractive complement to formalin in tissue processing and advocate its use in neuropathological practice.

The Diagnostic Use of Immunohistochemical Surrogates for Signature Molecular Genetic Alterations in Gliomas

A number of key mutations that affect treatment and prognosis have been identified in human gliomas. Two major ways to identify these mutations in a tumor sample are direct interrogation of the mutated DNA itself and immunohistochemistry to assess the effects of the mutated genes on proteins. Immunohistochemistry is an affordable, robust, and widely available technology that has been in place for decades. For this reason, the use of immunohistochemical approaches to assess molecular genetic changes has become an essential component of state-of-the-art practice. In contrast, even though DNA sequencing technologies are undergoing rapid development, many medical centers do not have access to such methodologies and may be thwarted by the relatively high costs of sending out such tests to reference laboratories. This review summarizes the current experience using immunohistochemistry of glioma samples to identify mutations in IDH1, TP53, ATRX, histone H3 genes, BRAF, EGFR, MGMT, CIC, and FUBP1 as well as guidelines for prudent use of DNA sequencing as a supplemental method.

Role of IL-6 in the invasiveness and prognosis of glioma

IL-6 is a cytokine secreted by glioma cells and plays an important role in the tumor growth. However, the impact of IL-6 on the invasiveness and prognosis of glioma is still unclear. In this study, immunohistochemistry was performed to determine the expression of IL-6 in 86 glioma tissues, and ELISA to measure IL-6 in the serum and cerebrospinal fluid (CSF) of these patients. Results showed, as ccompared with normal controls, the IL-6 in the glioma, CSF and serumincreased remarkably, and increased with the elevation of glioma grade. In addition, IL-6 in the supernatant was also detectable in glioma cell lines U251, U87, A172 and T98G. Transwell invasion assay showed that the invasiveness of glioma U87 cells and U251 cells increased remarkably after exogenous IL-6 treatment. Survival analysis indicated higher IL-6 before surgery and significantly reduction in IL-6 after operation in the serum and CSF predicted a poor prognosis. Thus, we speculate that, the poor prognosis of glioma is related to the IL-6 autocrine in the glioma and the IL-6 induced tumor growth and invasion. IL-6 may serve as a therapeutic target for glioma patients and IL-6 in the CSF and serum of glioma may be used to predict the prognosis of these patients.

Circulating glioma biomarkers

Validated biomarkers for patients suffering from gliomas are urgently needed for standardizing measurements of the effects of treatment in daily clinical practice and trials. Circulating body fluids offer easily accessible sources for such markers. This review highlights various categories of tumor-associated circulating biomarkers identified in blood and cerebrospinal fluid of glioma patients, including circulating tumor cells, exosomes, nucleic acids, proteins, and oncometabolites. The validation and potential clinical utility of these biomarkers is briefly discussed. Although many candidate circulating protein biomarkers were reported, none of these have reached the required validation to be introduced for clinical practice. Recent developments in tracing circulating tumor cells and their derivatives as exosomes and circulating nuclear acids may become more successful in providing useful biomarkers. It is to be expected that current technical developments will contribute to the finding and validation of circulating biomarkers.

Circulating biomarkers of CNS tumors: an update

CNS tumors comprise approximately 120 histological subtypes. Advances of surgical resection, radiation and systemic therapy have increased the survival rates of distinct types of CNS tumor patients. There is growing interest in identification of diagnostic, prognostic or predictive blood biomarkers in CNS tumor patients, and emerging studies indicate that certain brain tumors are indeed associated with distinct profiles of circulating factors such as proteins (e.g., glial fibrillary acidic protein), DNA fragments (e.g., containing mutated IDH) or miRNAs (e.g., miRNA-21). However, blood biomarker research in neurooncology is, for the most part, at an exploratory level, and adequately powered and well-designed studies are needed to translate the available interesting but preliminary findings into actual clinical use. In this review, the current knowledge on circulating biomarkers of CNS tumors is briefly summarized.