Glioma stem-like cells (GSCs) were first described as a population which may in part be resistant to traditional chemotherapeutic therapies and responsible for tumour regrowth. Knowledge of the underlying metabolic complexity governing GSC growth and function may point to potential differences between GSCs and the tumour bulk which could be harnessed clinically. There is an increasing interest in the direct/indirect targeting or reprogramming of GSC metabolism as a potential novel therapeutic approach in the adjuvant or recurrent setting to help overcome resistance which may be mediated by GSCs. In this review we will discuss stem-like models, interaction between metabolism and GSCs, and potential current and future strategies for overcoming GSC resistance.

An apparent “inverse” relationship exists between two seemingly unconnected conditions, Alzheimer’s disease (AD) and cancer, despite sharing similar risk factors, like increased age and obesity. AD is associated with amyloid beta (A$\mathsf{\beta }$) plaques and neurofibrillary tau tangles that cause neural degeneration; cancer, in contrast, is characterized by enhanced cell survival and proliferation. Apolipoprotein E (ApoE) is the main lipoprotein found in the central nervous system and via its high affinity with lipoprotein receptors plays a critical role in cholesterol transport and uptake. ApoE has 3 protein isoforms, ApoE E2, ApoE E3, and ApoE E4, respectively encoded for by 3 allelic variants of APOE ($\mathsf{\epsilon }$2, $\mathsf{\epsilon }$3, and $\mathsf{\epsilon }$4). This review examines the characteristics and function of ApoE described in both AD and cancer to assimilate evidence for its potential contribution to mechanisms that may underly the reported inverse association between the two conditions. Of the genetic risk factors relevant to most cases of AD, the most well-known with the strongest contribution to risk is APOE, specifically the $\mathsf{\epsilon }$4 variant, whereas for cancer risk, APOE has not featured as a significant genetic contributor to risk. However, at the protein level in both conditions, ApoE contributes to disease pathology via affecting lipid physiology and transport. In AD, A$\mathsf{\beta }$-dependent and -independent interactions have been suggested, whereas in cancer, ApoE plays a role in immunoregulation. Understanding the mechanism of action of ApoE in these diametrically opposed diseases may enable differential targeting of therapeutics to provide a beneficial outcome for both.

Background: The overall survival of IDH‐wildtype glioblastoma patients is poor despite best available treatments. There is an urgent need for new biomarkers to inform more precise disease stratification. Previous studies have identified insulin‐like growth factor binding protein‐2 (IGFBP‐2) as a potential biomarker for glioblastoma diagnosis and therapeutic targeting. Other studies have indicated links between the insulin‐like growth factor (IGF) axis and tumorigenic functions of a molecular chaperone glucose related protein of 78 kDa (GRP78). We aimed to interrogate the oncogenic effects of IGFBP‐2 and GRP78 in our glioma stem cell (GSC) lines and clinical cohort.Methods: Immunoblotting, reverse transcription quantitative real‐time PCR were used to quantify protein and mRNA levels derived from GSCs and non‐malignant neural stem cells (NSCs). Microarray analysis was used to compare the differences in IGFBP‐2 (IGFBP‐2) and GRP78 (HSPA5) transcript expression between NSCs, GSCs and adult human cortex samples. Immunohistochemistry was used to quantify IGFBP‐2 and GRP78 expression in IDH‐wildtype glioblastoma tissue sections (n = 92) and clinical implications assessed using survival analysis. Finally, the relationship between IGFBP‐2 and GRP78 was further explored molecularly using coimmunoprecipitation.Results: Here, we demonstrate that IGFBP‐2 and HSPA5 mRNA is overexpressed in GSCs and NSCs in comparison to non‐malignant brain tissue. We also determined a relationship in which G144 and G26 GSCs expressed higher IGFBP‐2 protein and mRNA than GRP78, and this was reversed in mRNA isolated from adult human cortex samples. Clinical cohort analysis revealed that Glioblastomas with high IGFBP‐2 protein expression paired with low GRP78 protein expression were significantly associated with a much shorter survival time (Median = 4 months, p = 0.019) compared with 12‐14 months for any other combination of high/low protein expression.Conclusions: Inverse levels of IGFBP‐2 and GRP78 may be adverse clinical prognostic markers in IDH‐wildtype glioblastoma. Further interrogation of the mechanistic link between IGFBP‐2 and GRP78 may be important for rationalisation of their potential as biomarkers and therapeutic targets.

Glioblastoma is a fatal and aggressive cancer with no cure. It is becoming increasingly clear that glioblastoma initiation is a result of adult neural stem cell (NSC) transformation—most likely those within the subventricular zone (SVZ). Indeed, transcriptomic analysis indicates that glioblastomas are reminiscent of a neurodevelopmental hierarchy, in which neural stem and progenitor markers are widely expressed by tumour stem-like cells. However, NSC fates and the cues that drive them are poorly understood. Studying the crosstalk within NSC niches may better inform our understanding of glioblastoma initiation and development. Insulin-like growth factor binding protein 2 (IGFBP-2) has a well-established prognostic role in glioblastoma, and cell-based mechanistic studies show the independent activation of downstream oncogenic pathways. However, IGFBP-2 is more commonly recognised as a modulator of insulin-like growth factors (IGFs) for receptor tyrosine kinase signal propagation or attenuation. In the adult human brain, both IGFBP-2 and IGF-II expression are retained in the choroid plexus (ChP) and secreted into the cerebral spinal fluid (CSF). Moreover, secretion by closely associated cells and NSCs themselves position IGFBP-2 and IGF-II as interesting factors within the NSC niche. In this review, we will highlight the experimental findings that show IGFBP-2 and IGF-II influence NSC behaviour. Moreover, we will link this to glioblastoma biology and demonstrate the requirement for further analysis of these factors in glioma stem cells (GSCs).

An apparent "inverse" relationship exists between two seemingly unconnected conditions: Alzheimer's disease (AD) and cancer, despite sharing similar risk factors, like increased age and obesity. AD is associated with amyloid beta (Aβ) plaques and neurofibrillary tau tangles that cause neural degeneration; cancer, in contrast, is characterised by enhanced cell survival and proliferation. Apolipoprotein E (ApoE) is the main lipoprotein found in the central nervous system and via its high affinity with lipoprotein receptors plays a critical role in cholesterol transport and uptake. ApoE has 3 protein isoforms: ApoE E2, ApoE E3, and ApoE E4, respectively encoded for by 3 allelic variants of APOE (ε2, ε3 and ε4). This review examines the characteristics and function of ApoE described in both AD and cancer, to assimilate evidence for its potential contribution to mechanisms that may underly the reported inverse association between the two conditions. Of the genetic risk factors relevant to most cases of AD, the most well-known with the strongest contribution to risk is APOE, specifically the ε4 variant, whereas for cancer risk, APOE has not featured as a significant genetic contributor to risk. Yet, at the protein level in both conditions, ApoE contributes to disease pathology via affecting lipid physiology and transport. In AD, Aβ-dependent and independent interactions have been suggested, whereas in cancer, ApoE plays a role in immunoregulation. Understanding the mechanism of action of ApoE in these diametrically opposed diseases, may enable differential targeting of therapeutics, to provide a beneficial outcome for both.