Metformin may offer no protective effect in men undergoing external beam radiation therapy for prostate cancer

Targeting lipid metabolism in metastatic prostate cancer

Despite key advances in the treatment of prostate cancer (PCa), a proportion of men have de novo resistance, and all will develop resistance to current therapeutics over time. Aberrant lipid metabolism has long been associated with prostate carcinogenesis and progression, but more recently there has been an explosion of preclinical and clinical data which is informing new clinical trials. This review explores the epidemiological links between obesity and metabolic syndrome and PCa, the evidence for altered circulating lipids in PCa and their potential role as biomarkers, as well as novel therapeutic strategies for targeting lipids in men with PCa, including therapies widely used in cardiovascular disease such as statins, metformin and lifestyle modification, as well as novel targeted agents such as sphingosine kinase inhibitors, DES1 inhibitors and agents targeting FASN and beta oxidation.

Prognostic value of metformin in cancers: An updated meta-analysis based on 80 cohort studies

BACKGROUND

Experiments have shown that metformin can inhibit cancer cell growth, but clinical observations have been inconsistent, so we pooled the currently available data to evaluate the impact of metformin on cancer survival and progression.

METHODS

PubMed, web of science, Embase, and Cochrane databases were searched. Pooled hazard ratios (HRs) were identified using a random-effects model to estimate the strength of the association between metformin and survival and progression in cancer patients.

RESULTS

We incorporated 80 articles published from all databases which satisfied the inclusion criterion. It showed that metformin was associated with better overall survival (hazard ratio [HR] = 0. 81; 95% confidence interval [CI]: [0.77-0.85]) and cancer-specific survival (HR = 0.79; 95% CI: [0.73-0.86]), and metformin was associated with progression-free survival (HR = 0.76; 95% CI: [0.66-0.87]). In patients with diabetes mellitus, the HR of overall survival was 0.79(95% CI: [0.75-0.83]), progression-free survival was 0.72(95% CI: [0.60-0.85]), and the cancer-specific survival was 0.76(95% CI: [0.68-0.86]). It was proposed that metformin can improve the prognosis of cancer patients with diabetes mellitus.

CONCLUSION

Based on cohort studies, metformin therapy has potential survival benefits for patients with malignancy, especially with the greatest benefits seen in breast cancer on overall survival, progression-free survival, and cancer-specific survival. And metformin also showed potential benefits in cancer-specific survival in colorectal and prostate cancer.

Association between baseline body mass index and survival in men with metastatic hormone-sensitive prostate cancer: ECOG-ACRIN CHAARTED E3805

BACKGROUND

E3805 (CHAARTED) is a phase 3 trial demonstrating improved survival for men with metastatic hormone-sensitive prostate cancer (mHSPC) randomized to treatment with docetaxel (D) and androgen-deprivation therapy (ADT) versus ADT alone. We assessed the association of baseline body mass index (BMI) and metformin exposure with quality of life (QOL) and prostate cancer outcomes including survival in patients enrolled in the CHAARTED study.

METHODS

We performed a posthoc exploratory analysis of the CHAARTED trial of men with mHSPC randomized to treatment with ADT with or without D between 2006 and 2012. Cox proportional hazards models and Kruskal-Wallis test were used to evaluate the association between BMI with QOL and prostate cancer outcomes and between metformin exposure and survival.

RESULTS

In 788 of 790 enrolled patients with prospectively recorded baseline BMI and metformin exposure status, lower BMI was not associated with survival, but was associated with high volume disease (p < 0.0001) and poorer baseline QOL on functional assessment of cancer therapy-prostate (p = 0.008). Only 68 patients had prevalent metformin exposure at baseline in the CHAARTED trial. Four groups were identified: ADT + D + metformin (n = 39); ADT + D (n = 357); ADT + metformin (n = 29); and ADT alone (n = 363). Baseline clinicopathologic characteristics were similar between groups. In this small exploratory multivariable analysis, metformin exposure was not associated with survival (hazard ratio: 1.15; 95% confidence interval: 0.81-1.63, p = 0.44).

CONCLUSIONS

There was no link between baseline BMI and survival, but lower baseline BMI was associated with features of greater cancer burden and poorer QOL.

Metformin mitigates PLCε gene expression and modulates the Notch1/Hes and androgen receptor signaling pathways in castration-resistant prostate cancer xenograft models

The present study aimed to establish a mouse model of patient-derived castration-resistant prostate cancer (CRPC) xenograft tumors, and to evaluate the effects of various doses of metformin on phospholipase Cε (PLCε) expression and the neurogenic locus notch homolog protein 1 (Notch1)/hairy and enhancer of split 1 and androgen receptor (AR) signaling pathways via western blotting and reverse transcription-quantitative PCR. Additionally, phorbol 12-myristate 13-acetate was used to activate PLC, and Jagged1 was used as a Notch activator to verify whether metformin could suppress CRPC development via the PLCε/Notch1/AR pathways. The results confirmed that metformin may serve critical roles in CRPC by significantly inhibiting the occurrence, growth and proliferation of CRPC tumors by decreasing PLCε/Notch1 expression and AR nucleation.

Lost in application: Measuring hypoxia for radiotherapy optimisation

The history of radiotherapy is intertwined with research on hypoxia. There is level 1a evidence that giving hypoxia-targeting treatments with radiotherapy improves locoregional control and survival without compromising late side-effects. Despite coming in and out of vogue over decades, there is now an established role for hypoxia in driving molecular alterations promoting tumour progression and metastases. While tumour genomic complexity and immune profiling offer promise, there is a stronger evidence base for personalising radiotherapy based on hypoxia status. Despite this, there is only one phase III trial targeting hypoxia modification with full transcriptomic data available. There are no biomarkers in routine use for patients undergoing radiotherapy to aid management decisions, and a roadmap is needed to ensure consistency and provide a benchmark for progression to application. Gene expression signatures address past limitations of hypoxia biomarkers and could progress biologically optimised radiotherapy. Here, we review recent developments in generating hypoxia gene expression signatures and highlight progress addressing the challenges that must be overcome to pave the way for their clinical application.

Long non-coding RNA SNHG8 promotes prostate cancer progression through repressing miR-384 and up-regulating HOXB7

BACKGROUND

Multiple long non-coding RNAs (lncRNAs) have been demonstrated to function as vital regulators in the progression of prostate cancer (PCa). In the present study, we aimed to probe the function of lncRNA small nucleolar RNA host gene 8 (SNHG8) in PCa progression.

METHODS

A quantitative real-time polymerase chain reaction and western blotting were utilized to measure SNHG8, microRNA-384 (miR-384) and homeobox B7 (HOXB7) expression. Call-couting kit-8 and bromodeoxyuridine experiments were employed to evaluate PCa cell proliferation. Transwell experiments were performed to detect PCa cell migration and invasion. Dual-luciferase reporter experiments and RNA immunoprecipitation experiments were conducted to determine the targeting relationships among miR-384, SNHG8 and HOXB7.

RESULTS

SNHG8 was up-regulated in PCa tissues and cells. Silencing of SNHG8 suppressed the proliferation, migration and invasion of PCa cells. SNHG8 functioned as a molecular sponge to repress miR-384. The effects of SNHG8 knockdown on PCa cell proliferation, migration and invasion were counteracted by miR-384 inhibition. HOXB7 was confirmed to be a target gene of miR-384. SNHG8 knockdown repressed HOXB7 expression via targeting miR-384.

CONCLUSIONS

SNHG8 promotes PCa cell proliferation, migration and invasion via decoying miR-384 and up-regulating HOXB7.

Metformin as a radiosensitiser for pelvic malignancy: A systematic review of the literature

BACKGROUND

The treatment of pelvic malignancies has continued to improve over recent years, with neoadjuvant radiotherapy often considered the gold standard to downstage disease. Radiosensitisers are routinely employed in an attempt to improve response of cancers to radiotherapy. Previous preclinical evidence has suggested a role for metformin, a commonly used drug for type 2 diabetes.

METHOD

A literature search was performed for published full text articles using the PubMed, Cochrane and Scopus databases using the search criteria string 'Metformin' AND ('Radiosensitivity' OR 'radiosensitising' OR 'radiosensitising'). Additional papers were detected by scanning the references of relevant papers. Data were extracted from each study by two authors onto a dedicated proforma. The review was registered on the PROSPERO database (ID: CRD42020199066).

RESULTS

A total of 242 papers were identified, 11 of which were included in this review; an additional 5 papers were obtained from reference searches. Metformin has been demonstrated to reduce cell-viability post-radiotherapy in both rectal and prostate cancer cell lines, with an enhanced effect in tumours with a p53 mutation and increased apoptosis post-radiotherapy for cervical cancer. Clinical trials demonstrate improved tumour and nodal downstaging and pCR rates for rectal cancer using metformin as a radiosensitiser.

CONCLUSION

With an increasing understanding of the underlying mechanism of the effects on metformin prospective studies are required to assess the effect of routine use on cancer related outcomes. Progressive future studies may be better served by the use of predictive biomarker guided treatment to enable identification of the appropriate cohort to target.

Current Status and Application of Metformin for Prostate Cancer: A Comprehensive Review

Metformin, an oral biguanide used for first-line treatment of type 2 diabetes mellitus, has attracted attention for its anti-proliferative and anti-cancer effects in several solid tumors, including prostate cancer (PCa). Liver kinase B1 (LKB1) and adenosine monophosphate-activated protein kinase (AMPK) activation, inhibition of the mammalian target of rapamycin (mTOR) activity and protein synthesis, induction of apoptosis and autophagy by p53 and p21, and decreased blood insulin level have been suggested as direct anti-cancer mechanisms of metformin. Research has shown that PCa development and progression are associated with metabolic syndrome and its components. Therefore, reduction in the risk of PCa and improvement in survival in metformin users may be the results of the direct anti-cancer mechanisms of the drug or the secondary effects from improvement of metabolic syndrome. In contrast, some research has suggested that there is no association between metformin use and PCa incidence or survival. In this comprehensive review, we summarize updated evidence on the relationship between metformin use and oncological effects in patients with PCa. We also highlight ongoing clinical trials evaluating metformin as an adjuvant therapy in novel drug combinations in various disease settings.

Impact of Concomitant Medications on Biochemical Outcome in Localised Prostate Cancer Treated with Radiotherapy and Androgen Deprivation Therapy

AIMS

Several classes of concomitant medications have been shown to affect oncological outcomes in patients with prostate cancer (PCa). We assessed the association between the use of commonly prescribed concomitant medications and biochemical relapse-free survival (bRFS) in patients with localised PCa treated with radiotherapy and androgen deprivation therapy (ADT).

MATERIALS AND METHODS

A secondary pooled analysis of two phase III randomised trials was carried out. In the first trial, patients with localised PCa with clinical stage T1b-T3, prostate-specific antigen <30 ng/ml and Gleason score ≤7 were treated with radical radiotherapy and 6 months of ADT starting 4 months before or concomitantly with radiotherapy. In the second trial, patients with high-risk PCa were treated with radical radiotherapy and 36 months of ADT with randomisation to three-dimensional conformal or intensity-modulated radiotherapy. Information on concomitant medications was collected from the medical record. Univariable and multivariable Cox regression was used to identify factors associated with bRFS.

RESULTS

Overall, 486 patients were evaluable. The median follow-up was 125 months; 10-year bRFS was 83.7%. On univariable analysis, receipt of metformin was significantly associated with worse bRFS. Ten-year bRFS was 73% and 85% for patients with and without concomitant metformin (adjusted hazard ratio 2.11, 95% confidence interval 1.03-4.33). Similar evidence of an association was observed with sulfonamide-based α1-receptor blockers (adjusted hazard ratio 2.72, 95% confidence interval 1.31-5.66). However, no such association was seen with receipt of quinazoline-based α1-receptor blockers (adjusted hazard ratio 1.09, 95% confidence interval 0.42-2.82). There was no significant association between bRFS and receipt of all other medication classes considered.

CONCLUSIONS

In this population of patients with localised PCa treated with radiotherapy and ADT, receipt of concomitant metformin and sulfonamide-based α1-receptor blockers was associated with inferior biochemical outcome. Randomised trials are required to assess the true effect of these medications on oncological outcomes in localised PCa.

Metformin: (future) best friend of the radiation oncologist?

Several molecules are being investigated for their ability to enhance the anti-tumor effect of radiotherapy. The widely prescribed antidiabetic drug metformin has been suggested to possess anti-cancer activity; data indicate that metformin could also enhance radiation sensitivity. The purpose of this review is to summarize current knowledge on the specific effect of metformin in the field of RT, while also discussing the many unknowns that persist. Preclinical models point to multiple mechanisms involved in the radiosensitizing effects of metformin that are mainly linked to mitochondrial complex I inhibition and AMP-activated protein kinase. Transposition of results from bench to bedside will be discussed through the lens of the drug concentration, its potential limits in human settings, and possible alternatives. Clinical data suggest metformin improves progression-free and overall survival in patients for many different cancers treated with RT; nevertheless, the results are not always consistent. The main limitations of the reviewed literature are the retrospective nature of studies, and most of the time, a lack of information on MTF treatment duration and the administered dosages. Despite these limitations, the possible mechanisms of the role of metformin and its utility in enhancing radiotherapy treatments are analyzed. Ongoing clinical trials are also discussed.