心磷脂酰基链重塑是侵袭性婴儿胚胎性脑肿瘤的治疗靶点

Background: Pediatric embryonal brain tumors that impact infants are highly aggressive CNS WHO grade 4 neoplasms with no standard-of-care. These encompass embryonal tumor with multilayered rosettes (ETMR), atypical teratoid rhabdoid tumor (AT/RT), group 3 medulloblastoma (MB-G3) and recurrent/metastatic sonic hedgehog medulloblastoma (MB-SHH). These tumors have low inter-tumoral genetic heterogeneity yet present with diverse histological features and developmental locations within the brain, which makes identifying therapeutic targets a challenge. The mechanisms driving therapeutic resistance for currently used treatment regimens are unknown. New and more effective treatments are urgently needed. Cardiolipins are mitochondrial-specific lipids, and their fatty acid composition has been shown to regulate mitochondrial structure and function. Despite the known functional significance of cardiolipins, their structure-specific accumulation in relation to mitochondrial phenotypes and cellular function in aggressive pediatric embryonal brain tumors remain ill-defined. Methods: Spatial lipidomic profiles in patient samples and 3D models were determined using mass spectrometry imaging. Cell proliferation and mitochondrial bioenergetics and dynamics were characterized using multiplex immunofluorescence (mIF), transmission electron microscopy, western blotting and metabolic assays. LCLAT1 KD was carried out using siRNA and inducible shRNA. Results: We detected a structure-specific accumulation of cardiolipins and increased expression of the cardiolipin acyl chain remodeling enzyme, LCLAT1 within proliferating tumor cells in patient samples and the 3D tumorspheres. The mitochondria in the proliferating tumor cells were fragmented and displayed a tubular cristae architecture. LCLAT1 KD in ETMR altered cardiolipin profiles, significantly reduced 3D tumorsphere growth, decreased Sox2 and N-Myc expression, increased p53 and p21 expression, and significantly increased LIN28A expression with a parallel increase in the early neuronal marker, doublecortin. Conclusions: Our findings provide novel insight into aggressive infantile embryonal brain tumor biology based on mitochondrial phenotypes and the fatty acid composition of the multifunctional mitochondrial-specific lipid, cardiolipin. We additionally showed evidence of a switch from a stem cell phenotype to upregulated neuronal differentiation pathways following CL fatty acyl chain remodeling in ETMR. Our findings underscore the intimate relationship between CL structure, mitochondrial phenotypes and embryonal brain tumor cell fate. On-going studies: Determine the in vivo and in vitro functional significance of cardiolipin acyl chain remodeling in ETMR and AT/RT, with a focus on LIN28A and differentiation pathways.