Targeting metabolic plasticity in glioma stem cells in vitro and in vivo through specific inhibition of c-Src by TAT-Cx43266-283

Abstract

Background Glioblastoma is the most aggressive primary brain tumour and has a very poor prognosis. Inhibition of c-Src activity in glioblastoma stem cells (GSCs, responsible for glioblastoma lethality) and primary glioblastoma cells by the peptide TAT-Cx43 266–283 reduces tumorigenicity, and boosts survival in preclinical models. Because c-Src can modulate cell metabolism and several reports revealed poor clinical efficacy of various antitumoral drugs due to metabolic rewiring in cancer cells, here we explored the inhibition of advantageous GSC metabolic plasticity by the c-Src inhibitor TAT-Cx43 266-283 . Methods Metabolic impairment induced by the c-Src inhibitor TAT-Cx43 266-283 in vitro was assessed by fluorometry, western blotting, immunofluorescence, qPCR, enzyme activity assays, electron microscopy, Seahorse analysis, time-lapse imaging, siRNA, and MTT assays. Protein expression in tumours from a xenograft orthotopic glioblastoma mouse model was evaluated by immunofluorescence. Findings TAT-Cx43 266–283 decreased glucose uptake in human GSCs and reduced oxidative phosphorylation without a compensatory increase in glycolysis, with no effect on brain cell metabolism, including rat neurons, human and rat astrocytes, and human neural stem cells. TAT-Cx43 266-283 impaired metabolic plasticity, reducing GSC growth and survival under different nutrient environments. Finally, GSCs intracranially implanted with TAT-Cx43 266–283 showed decreased levels of important metabolic targets for cancer therapy, such as hexokinase-2 and GLUT-3. Interpretation The reduced ability of TAT-Cx43 266-283 –treated GSCs to survive in metabolically challenging settings, such as those with restricted nutrient availability or the ever-changing in vivo environment, allows us to conclude that the advantageous metabolic plasticity of GSCs can be therapeutically exploited through the specific and cell-selective inhibition of c-Src by TAT-Cx43 266-283 . Funding Spanish Ministerio de Economía y Competitividad (FEDER BFU2015-70040-R and FEDER RTI2018-099873-B-I00), Fundación Ramón Areces. Fellowships from the Junta de Castilla y León, European Social Fund, Ministerio de Ciencia and Asociación Española Contra el Cáncer (AECC).

Connexin 43 peptidic medicine for glioblastoma stem cells

“…Moreover, αCT1 selectively inactivates phosphoinositide 3-kinase catalytic subunit β (PIK3CB, also called PI3Kβ or p110β) in temozolomide-resistant GSCs [9] and a combination of αCT1 and temozolomide obstructs the self-renewal and tumorigenicity of GSCs [10] . In line with the results of TAT-Cx43 266–283 in GSCs described above [ 4 , 5 ], Cx43-CT is vital to GSCs. Because JM2 and αCT1 exhibit negligible toxicity to normal neural stem cells, same as TAT-Cx43 266–283 [8] , [9] , [10] , targeting Cx43-CT represents a powerful and feasible therapeutic approach for selectively eliminating GSCs.…”

“…Eliminating GSCs is therefore an appealing therapeutic approach; however, targeting GSCs is challenging given their idiosyncratic nature that makes GSCs metabolically resilient compared to differentiated tumor cells and endows GSCs survival advantages particularly under unfavorable growth conditions. Recent research from Pelaz and her colleagues has provided possible answers to this challenge and offered a new therapeutic opportunity that allows us to eliminate dormant and resilient GSCs [4] .…”

“…The activation of c-SRC subsequently promotes the motility, growth, and tumorigenicity of GSCs in vitro and in vivo [6] . Given that c-SRC plays a vital role in regulating metabolism in cancer, Pelaz et al, tested the hypothesis that Cx43-CT regulates GSCs’ metabolic activity [4] . By treating GSCs with TAT-Cx43 266–283 , a Cx43 CT-mimetic peptide that inactivates c-SRC [6] , they have demonstrated that TAT-Cx43 266–283 decreases the hexokinase-dependent/glucose transporter-independent uptake of glucose and induces a temporal and spatial change of mitochondria localization and function.…”

The Importance of Tumor Stem Cells in Glioblastoma Resistance to Therapy

“…GSCs and GBM cells utilize and express different Src family members of protein tyrosine kinases (SFKs), including Src, Fyn, Yes, and Lyn, and their effects do not always seem to be functionally superfluous. Inhibition of Src family activity in GSCs, responsible for GBM lethality and primary GBM cells, reduces tumorigenicity and boosts survival in preclinical models [ 46 , 47 , 48 ].…”

“…The standard treatment for GBM [ 105 ] is largely ineffective, and the average survival of a person diagnosed with GBM is only 15 months. Current therapies against GBM show a high percentage of failure associated with the survival of GSCs that repopulate treated tumors [ 47 ]. Some evidence suggests that new therapeutic approaches are required to contrast tumor heterogeneity, drug resistance, and a complex tumor-supporting microenvironment, and improve survival and quality of life.…”