The Cancer Driver Genes IDH1 and IDH2 and CD204 in WHO-Grade 4 Astrocytoma: Crosstalk Between Cancer Metabolism and Tumour Associated Macrophage Recruitment in Tumour Microenvironment.

Purpose: IDH1 and IDH2 are hotspot mutations commonly identified in WHO-grade 4 astrocytomas. Their association with TAMs has never been investigated. We aim to explore the crosstalk between the IDH1/2 mutation metabolic effect and TAMs in tumour microenvironment and how this relationship affects the tumour recurrence.

Patients and methods: The study included 20 samples of patients with WHO-grade 4 astrocytoma. The alteration hotspot in codon IDH1^R132 and IDH2^R172 was examined using direct sequencing. The protein expression of CD204 on TAM was detected through immunohistochemistry.

Results: IDH1^R132 and IDH2^R172 were symmetrically identified as wildtype in 18/20 tumours (90%) and the remaining 2 tumours (10%) showed synonymous mutations on both codons. Tumours with IDH1/2-wildtype showed high expression of CD204⁺TAMs in 10 cases and low expression in 8 cases. Typical expression was seen equally in IDH1/2 mutant tumours. There was no significant association between IDH1/2 and CD204⁺TAM expression (p= 0.999). The association between the two groups was significantly observed among IDH-wildtype tumours (p=0.027). Highly expressed CD204 in IDH-wildtype tumours showed a median recurrence at 10 months compared to low CD204 expression, showed a median recurrence interval at 24 months.

Conclusion: IDH1^R132 or IDH^R172 has the same impact on the classification and prognosis of WHO-grade 4 astrocytoma. There was no crosstalk between IDH1/2 metabolic effect and CD204⁺TAM. However, IDH-wildtype glioblastomas with dense CD204⁺TAM are associated with early recurrence. Because the sample size is small, a larger study is recommended to determine the impact of IDH1/2 on TAMs.