Efficacy and safety of metformin plus low-dose temozolomide in patients with recurrent or refractory glioblastoma: a randomized, prospective, multicenter, double-blind, controlled, phase 2 trial (KNOG-1501 study)

Metabolic Reprogramming in Glioblastoma Multiforme: A Review of Pathways and Therapeutic Targets

Glioblastoma (GBM) is an aggressive and highly malignant primary brain tumor characterized by rapid growth and a poor prognosis for patients. Despite advancements in treatment, the median survival time for GBM patients remains low. One of the crucial challenges in understanding and treating GBMs involves its remarkable cellular heterogeneity and adaptability. Central to the survival and proliferation of GBM cells is their ability to undergo metabolic reprogramming. Metabolic reprogramming is a process that allows cancer cells to alter their metabolism to meet the increased demands of rapid growth and to survive in the often oxygen- and nutrient-deficient tumor microenvironment. These changes in metabolism include the Warburg effect, alterations in several key metabolic pathways including glutamine metabolism, fatty acid synthesis, and the tricarboxylic acid (TCA) cycle, increased uptake and utilization of glutamine, and more. Despite the complexity and adaptability of GBM metabolism, a deeper understanding of its metabolic reprogramming offers hope for developing more effective therapeutic interventions against GBMs.

Preclinical and clinical advances to overcome hypoxia in glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most common adult primary brain tumor. The standard clinical treatment of GBM includes a maximal surgical resection followed by concomitant radiotherapy (RT) and chemotherapy sessions with Temozolomide (TMZ) in addition to adjuvant TMZ cycles. Despite the severity of this protocol, GBM is highly resistant and recurs in almost all cases while the protocol remains unchanged since 2005. Limited-diffusion or chronic hypoxia has been identified as one of the major key players driving this aggressive phenotype. The presence of hypoxia within the tumor bulk contributes to the activation of hypoxia signaling pathway mediated by the hypoxia-inducing factors (HIFs), which in turn activate biological mechanisms to ensure the adaptation and survival of GBM under limited oxygen and nutrient supply. Activated downstream pathways are involved in maintaining stem cell-like phenotype, inducing mesenchymal shift, invasion, and migration, altering the cellular and oxygen metabolism, and increasing angiogenesis, autophagy, and immunosuppression. Therefore, in this review will discuss the recent preclinical and clinical approaches that aim at targeting tumor hypoxia to enhance the response of GBM to conventional therapies along with their results and limitations upon clinical translation.

Role of renin angiotensin system inhibitors and metformin in Glioblastoma Therapy: a review

Glioblastoma multiforme (GBM) is a highly aggressive and incurable disease accounting for about 10,000 deaths in the USA each year. Despite the current treatment approach which includes surgery with chemotherapy and radiation therapy, there remains a high prevalence of recurrence. Notable improvements have been observed in persons receiving concurrent antihypertensive drugs such as renin angiotensin inhibitors (RAS) or the antidiabetic drug metformin with standard therapy. Anti-tumoral effects of RAS inhibitors and metformin have been observed in in vitro and in vivo studies. Although clinical trials have shown mixed results, the potential for the use of RAS inhibitors and metformin as adjuvant GBM therapy remains promising. Nevertheless, evidence suggest that these drugs exert multimodal antitumor actions; by particularly targeting several cancer hallmarks. In this review, we highlight the results of clinical studies using multidrug cocktails containing RAS inhibitors and or metformin added to standard therapy for GBM. In addition, we highlight the possible molecular mechanisms by which these repurposed drugs with an excellent safety profile might elicit their anti-tumoral effects. RAS inhibition elicits anti-inflammatory, anti-angiogenic, and immune sensitivity effects in GBM. However, metformin promotes anti-migratory, anti-proliferative and pro-apoptotic effects mainly through the activation of AMP-activated protein kinase. Also, we discussed metformin's potential in targeting both GBM cells as well as GBM associated-stem cells. Finally, we summarize a few drug interactions that may cause an additive or antagonistic effect that may lead to adverse effects and influence treatment outcome.

Factors associated with longer survival among older medicare patients after diagnosis of supratentorial primary brain malignancies: a retrospective cohort study

OBJECTIVES

Despite recent advances, the prognosis for primary malignant brain tumors (PMBTs) remains poor. Some commonly prescribed medications may exhibit anti-tumor properties in various cancers, and neurodegenerative diseases may activate pathways that counteract gliomagenesis. Our study is focused on determining if there is a correlation between the use of metformin, beta-blockers, angiotensin converting enzyme inhibitors (ACEIs), and angiotensin receptor blockers (ARBs), or the presence of Parkinson's disease (PD), and the survival rates following a diagnosis of a PMBT.

METHODS

This analysis of the 100% Texas Medicare Database identified patients aged 66+ years diagnosed with a supratentorial PMBT from 2014-2017. Cox proportional hazards regression was employed to analyze survival following diagnosis and associations of survival with surgical intervention, radiation, PD diagnosis, and prescription of metformin, beta-blockers, ACEIs, or ARBs.

RESULTS

There were 1,943 patients who met study criteria, and the median age was 74 years. When medication utilization was stratified by none, pre-diagnosis only, post-diagnosis only, or both pre- and post-diagnosis (continuous), continuous utilization of metformin, beta-blockers, ACEIs, or ARBs was associated with prolonged survival compared to no utilization (hazard ratio [HR]:0.45, 95% CI:0.33-0.62; HR:0.71. 95% CI:0.59-0.86; HR:0.59, 95% CI:0.48-0.72; and HR:0.45, 95% CI:0.35-0.58 respectively). PD was also associated with longer survival (HR:0.59-0.63 across the four models).

DISCUSSION

Our study suggests that metformin, beta-blockers, ACEIs, ARBs, and comorbid PD are associated with a survival benefit among geriatric Medicare patients with supratentorial PMBTs.

Metformin: A Dual-Role Player in Cancer Treatment and Prevention

Cancer continues to pose a significant global health challenge, as evidenced by the increasing incidence rates and high mortality rates, despite the advancements made in chemotherapy. The emergence of chemoresistance further complicates the effectiveness of treatment. However, there is growing interest in the potential of metformin, a commonly prescribed drug for type 2 diabetes mellitus (T2DM), as an adjuvant chemotherapy agent in cancer treatment. Although the precise mechanism of action of metformin in cancer therapy is not fully understood, it has been found to have pleiotropic effects, including the modulation of metabolic pathways, reduction in inflammation, and the regulation of cellular proliferation. This comprehensive review examines the anticancer properties of metformin, drawing insights from various studies conducted in vitro and in vivo, as well as from clinical trials and observational research. This review discusses the mechanisms of action involving both insulin-dependent and independent pathways, shedding light on the potential of metformin as a therapeutic agent for different types of cancer. Despite promising findings, there are challenges that need to be addressed, such as conflicting outcomes in clinical trials, considerations regarding dosing, and the development of resistance. These challenges highlight the importance of further research to fully harness the therapeutic potential of metformin in cancer treatment. The aims of this review are to provide a contemporary understanding of the role of metformin in cancer therapy and identify areas for future exploration in the pursuit of effective anticancer strategies.

Cardiovascular/anti-inflammatory drugs repurposed for treating or preventing cancer: A systematic review and meta-analysis of randomized trials

BACKGROUND

Due to encouraging pre-clinical data and supportive observational studies, there has been growing interest in applying cardiovascular drugs (including aspirin, angiotensin-converting enzyme [ACE] inhibitors, statins, and metformin) approved to treat diseases such as hypertension, hyperlipidemia, and diabetes mellitus to the field of oncology. Moreover, given growing costs with cancer care, these medications have offered a potentially more affordable avenue to treat or prevent recurrence of cancer. We sought to investigate the anti-cancer effects of drugs repurposed from cardiology or anti-inflammatories to treat cancer. We specifically evaluated the following drug classes: HMG-CoA reductase inhibitors (statins), cyclo-oxygenase inhibitors, aspirin, metformin, and both angiotensin receptor blockers (ARBs) and angiotensin-converting enzyme inhibitors. We also included non-steroidal anti-inflammatory drugs (NSAIDs) because they exert a similar mechanism to aspirin by blocking prostaglandins and reducing inflammation that is thought to promote the development of cancer.

METHODS

We performed a systematic literature review using PubMed and Web of Science with search terms including "aspirin," "NSAID," "statin" (including specific statin drug names), "metformin," "ACE inhibitors," and "ARBs" (including specific anti-hypertensive drug names) in combination with "cancer." Searches were limited to human studies published between 2000 and 2023.

MAIN OUTCOMES AND MEASURES

The number and percentage of studies reported positive results and pooled estimates of overall survival, progression-free survival, response, and disease-free survival.

RESULTS

We reviewed 3094 titles and included 67 randomized clinical trials. The most common drugs that were tested were metformin (n = 21; 30.9%), celecoxib (n = 20; 29.4%), and simvastatin (n = 8; 11.8%). There was only one study that tested cardiac glycosides and none that studied ACE inhibitors. The most common tumor types were non-small-cell lung cancer (n = 19; 27.9%); breast (n = 8; 20.6%), colorectal (n = 7; 10.3%), and hepatocellular (n = 6; 8.8%). Most studies were conducted in a phase II trial (n = 38; 55.9%). Most studies were tested in metastatic cancers (n = 49; 72.1%) and in the first-line setting (n = 36; 521.9%). Four studies (5.9%) were stopped early because of difficulty with accrual. The majority of studies did not demonstrate an improvement in either progression-free survival (86.1% of studies testing progression-free survival) or in overall survival (94.3% of studies testing overall survival). Progression-free survival was improved in five studies (7.4%), and overall survival was improved in three studies (4.4%). Overall survival was significantly worse in two studies (3.8% of studies testing overall survival), and progression-free survival was worse in one study (2.8% of studies testing progression-free survival).

CONCLUSIONS AND RELEVANCE

Despite promising pre-clinical and population-based data, cardiovascular drugs and anti-inflammatory medications have overall not demonstrated benefit in the treatment or preventing recurrence of cancer. These findings may help guide future potential clinical trials involving these medications when applied in oncology.

Survival Impact of Combined Biguanide and Temozolomide in Glioblastoma Preclinical Models: A Systematic Review and Meta-Analysis

BACKGROUND

Glioblastoma (GBM) is an aggressive tumor known for its poor prognosis. Despite extensive research into its molecular and clinical aspects, the current management strategies have shown limited efficacy in improving survival rate. Despite some preclinical studies exploring the combination of temozolomide (TMZ) with biguanides such as metformin (MET) and others, the potential benefits of this combination remain uncertain. The aim of this study is to evaluate the overall survival (OS) in GBM murine-models treated with a combination of TMZ + biguanide compared to those treated with TMZ alone.

METHODS

We systematically searched Medline, Embase, and Lilacs databases for studies comparing TMZ + biguanide versus TMZ alone in GBM models and reporting OS data. The mean difference (MD) with 95% confidence interval and random-effects model was adopted.

RESULTS

Nine studies were included in this systematic review. The meta-analysis comprised 6 studies involving 85 rat-models, with 45 subjects undergoing combined-treatment. GBM-murine models treated with TMZ + biguanide exhibited notably superior OS rates compared to those who received TMZ alone, showing an MD of 21.0 days (6.9-35.0). Within the subgroup of orthotopic models, the OS was also significantly better in combination-therapy with an MD of 23.7 days (6.5-40.9). Similarly, in the subgroup where MET was used as biguanide therapy, TMZ + MET demonstrated a significant increase in OS, with an MD of 27.4 days (6.0-48.8). In immunocompromised models, the combination-therapy also exhibited higher survival rates, with an MD of 13 days (9.4-16.6).

CONCLUSIONS

This systematic review and meta-analysis provide compelling evidence regarding the beneficial effects of TMZ + biguanide in GBM models compared with TMZ alone, resulting in a significant improvement in OS.