Investigating the effects of PTEN mutations on cGAS-STING pathway in glioblastoma tumours

BACKGROUND

PTEN is a tumour suppressor gene and well-known for being frequently mutated in several cancer types. Loss of immunogenicity can also be attributed to PTEN loss, because of its role in establishing the tumour microenvironment. Therefore, this study aimed to represent the link between PTEN and cGAS-STING activity, a key mediator of inflammation, in tumour samples of glioblastoma patients.

METHODS

Tumour samples of 36 glioblastoma patients were collected. After DNA isolation, all coding regions of PTEN were sequenced and analysed. PTEN expression status was also evaluated by qRT-PCR, western blot, and immunohistochemical methods. Interferon-stimulated gene expressions, cGAMP activity, CD8 infiltration, and Granzyme B expression levels were determined especially for the evaluation of cGAS-STING activity and immunogenicity.

RESULTS

Mutant PTEN patients had significantly lower PTEN expression, both at mRNA and protein levels. Decreased STING, IRF3, NF-KB1, and RELA mRNA expressions were also found in patients with mutant PTEN. Immunohistochemistry staining of PTEN displayed expressional loss in 38.1% of the patients. Besides, patients with PTEN loss had considerably lower amounts of IFNB and IFIT2 mRNA expressions. Furthermore, CD8 infiltration, cGAMP, and Granzyme B levels were reduced in the PTEN loss group.

CONCLUSION

This study reveals the immunosuppressive effects of PTEN loss in glioblastoma tumours via the cGAS-STING pathway. Therefore, determining the PTEN status in tumours is of great importance, like in situations when considering the treatment of glioblastoma patients with immunotherapeutic agents.

A novel bi-allelic variant in the SDHB gene causes a severe mitochondrial complex II deficiency: a case report

Isolated deficiency of complex II is a rare inborn error of metabolism, accounting for approximately 2% of mitochondrial diseases. Mitochondrial complex II deficiency is predominantly seen in cases with bi-allelic SDHA mutations. To our knowledge, only 11 patients and five pathogenic variants have been reported for the SDHB gene. Our patient had a severe clinical presentation with seizures and sepsis, and died at the age of 2 months. Muscle biopsy analysis was compatible with mitochondrial myopathy with complex II deficiency. The family was given a molecular diagnosis for their child 2 years after his death via a clinical exome test of a frozen muscle biopsy specimen and a novel homozygous missense variant c.592 A>G (p.Ser198Gly) in SDHB gene was detected by next-generation sequencing. Here, we present another patient with a novel homozygous SDHB variant causing severe complex II deficiency and early death.

Mutation spectrum of the NF1 gene and genotype-phenotype correlations in Turkish patients: Seventeen novel pathogenic variants

OBJECTIVE

Neurofibromatosis type 1 is one of the most common autosomal dominant diseases caused by heterozygous mutation in the NF1 gene. Wide spectrum of NF1-related clinical manifestations and mutation distribution makes genetic counselling difficult.

METHODS

The study enrolled 58 unrelated Turkish patients with clinically suspected NF1 referred to the Department of Medical Genetics. Individuals were eligible if they 1) met at least two of the main National Institutes of Health criteria or 2) had multiple café-au-lait macules as a child.

RESULTS

Fourty-one different disease-causing variants were identified in 42 (72.4%) individuals, including 17 novel variants. Twenty-four (58.2%) of the NF1 patients had de novo variants. Café-au-lait macules were observed in all patients (100%). Intracranial hamartoma was the second most common phenotype, found in 52.3% (22/42) of the patients. Other common manifestations were neurofibromas (35.7%), axillary or inguinal freckling (28.5%), and Lisch nodules (28.5%). Additionally, one patient had intra-abdominal malignant peripheral nerve sheath tumours and another patient underwent surgery for serous papillary ovarian cancer.

CONCLUSION

In conclusion, this study is one of the largest studies from Turkey to investigate the NF1 mutation spectrum and genotype-phenotype correlations.