Search

Introduction: Prostate Specific Membrane Antigen (PSMA) - positron emission tomography (PET) guides metastasis - directed radiotherapy (MDRT) in prostate cancer (PrCa). However, its value as a treatment response assessment tool after MDRT remains unclear. Importantly, there is limited understanding of the potential of radiotherapy (RT) to alter PSMA gene (folate hydrolase 1; FOLH1) expression. Methods: We reviewed a series of 11 men with oligo - metastatic PrCa (25 metastasis sites) treated with MDRT before re - staging with 18F - DCFPyL (PSMA) PET upon secondary recurrence. Acute effects of RT on PSMA protein and mRNA levels were examined with qPCR and immunoblotting in human wild - type androgen - sensitive (LNCap), castrate - resistant (22RV1) and castrate - resistant neuroendocrine (PC3 and DU145) PrCa cell lines. Xenograft tumors were analyzed with immunohistochemistry. Further, we examined PSMA expression in untreated and irradiated radio - resistant (RR) 22RV1 (22RV1 - RR) and DU145 (DU145 - RR) cells and xenografts selected for survival after high - dose R. Results: The majority of MDRT - treated lesions showed lack of PSMA - PET/CT avidity, suggesting treatment response even after low biological effective dose (BED) MDRT. We observed similar high degree of heterogeneity of PSMA expression in both human specimens and in xenograft tumors. PSMA was highly expressed in LNCap and 22RV1 cells and tumors but not in the neuroendocrine PC3 and DU145 models. Single fraction RT caused detectable reduction in PSMA protein but not in mRNA levels in LNCap cells and did not significantly alter PSMA protein or mRNA levels in tissue culture or xenografts of the other cell lines. However, radio - resistant 22RV1 - RR cells and tumors demonstrated marked decrease of PSMA transcript and protein expression over their parental counterparts. Conclusions: PSMA - PET may be a promising tool to assess RT response in oligo - metastatic PrCa. However, future systematic investigation of this concept should recognize the high degree of heterogeneity of PSMA expression within prostate tumors and the risk for loss of PSMA expression in tumor surviving curative courses of RT. [ABSTRACT FROM AUTHOR]

We describe the case of a 75-year-old patient who progressed over a 12-year period from localized to symptomatic metastatic prostate cancer (PrCa) with lung as the sole organ of involvement. In this case, the specific sequence of positron emission tomography (PET)-based next-generation imaging with 18F-sodium fluoride-, 18F-fluoro-2-deoxy-D-glucose-, and 18F-DCFPyL PET/computed tomography and biopsies allowed illustration of the pathway of disease progression from nonglycolytic hormone-sensitive PrCa to glycolytic castrate-resistant PrCa without neuroendocrine features. The observations provide a unique insight into the timelines of anatomical and metabolic progression of metastatic PrCa. They highlight the value of close radiographic surveillance of metastatic PrCa with modern imaging to guide early treatment interventions. [ABSTRACT FROM AUTHOR]

Stimulation of the energy sensor AMP-activated kinase (AMPK) has been viewed as a targeted approach to increase glucose uptake by skeletal muscle and control blood glucose homeostasis. Rosemary extract (RE) has been reported to activate AMPK in hepatocytes and reduce blood glucose levels in vivo but its effects on skeletal muscle are not known. In the present study, we examined the effects of RE and the mechanism of regulation of glucose uptake in muscle cells. RE stimulated glucose uptake in L6 myotubes in a dose- and time-dependent manner. Maximum stimulation was seen with 5 μg/mL of RE for 4 h (184% ± 5.07% of control, p < 0.001), a response comparable to maximum insulin (207% ± 5.26%, p < 0.001) and metformin (216% ± 8.77%, p < 0.001) stimulation. RE did not affect insulin receptor substrate 1 and Akt phosphorylation but significantly increased AMPK and acetyl-CoA carboxylase phosphorylation. Furthermore, the RE-stimulated glucose uptake was significantly reduced by the AMPK inhibitor compound C, but remained unchanged by the PI3K inhibitor, wortmannin. RE did not affect GLUT4 or GLUT1 glucose transporter translocation in contrast with a significant translocation of both transporters seen with insulin or metformin treatment. Our study is the first to show a direct effect of RE on muscle cell glucose uptake by a mechanism that involves AMPK activation. [ABSTRACT FROM AUTHOR]

Introduction: Growth differentiation factor 15 (GDF15) is a cytokine of the TGFβ family. Here, we analyzed GDF15 levels in patients with locally advanced non-small cell lung cancer (LA-NSCLC) who participated in OCOG-ALMERA (NCT02115464), a phase II randomized clinical trial, that investigated metformin in combination with standard of care concurrent chemoradiotherapy (cCRT). OCOG-ALMERA was not able to demonstrate benefit in the metformin arm. Therefore, biomarker studies are needed to better define stratification parameters for future trials. Methods: Patients were randomized to treatment with platinum-based chemotherapy and concurrent chest radiotherapy (60–66 Gy), with or without metformin (2000 mg/d). The trial collected tumor volume parameters, survival outcomes, and patient blood plasma at baseline, during (weeks 1 and 6) and 6 months after cCRT. Plasma GDF15 levels were assayed with the ELISA method. Statistical analyses explored associations between GDF15, survival outcomes, and radiotherapy tumor volumes. Results: Baseline plasma levels of GDF15 were elevated in study patients, they increased during cCRT (p < 0.001), and the addition of metformin was associated with a further increase (week 6, p = 0.033). Baseline GDF15 levels correlated with the radiotherapy gross target volume (GTV, p < 0.01), while week 1 of radiotherapy levels correlated with radiotherapy planned target volume (PTV, p < 0.006). In multivariate analysis, baseline plasma GDF15 was prognostic for poor relapse-free (RFS) and overall survival (OS) (p = 0.005 and p = 0.002, respectively). Conclusions: GDF15 is a plasma marker that responds to the treatment of unresected LA-NSCLC with cCRT and metformin. GDF15 levels correspond with tumor volume and increased GDF15 levels predict for poor RFS and OS. These results require validation in larger clinical trial datasets. Highlights: Analysis of plasma specimens of OCOG-ALMERA, a phase II clinical trial that investigated metformin in combination with standard of care concurrent chemoradiotherapy, suggests that the cytokine growth differentiation factor 15 (GDF15) may be a promising biomarker in unresected locally advanced non-small cell lung cancer (LA-NSCLC). GDF15 levels increased during chemoradiotherapy, did more so in metformin-treated patients and corresponded with the radiotherapy clinical target volumes. Baseline plasma levels of GDF15 predicted overall and relapse-free survival. Validation of these results within larger clinical trials could lead to the establishment of an easily assessable plasma biomarker that could guide LA-NSCLC treatment in the future. [ABSTRACT FROM AUTHOR]

Provides information on a study on 2,4-Dinitrophenol. Materials used in the study; Methodology; Results of the study.

Focuses on a study which used 2,4-dinitrophenol (DNP) as a model of exercise or hypoxia to investigate possible mediators of this alternative signaling pathway. Materials and methods; Distinct pathways for glucose transport stimulation; Discussion of the results.

Provides information on a study which addressed the effects of long-term treatment with insulin on glucose transporter expression in L6 muscle cells as well as the signaling pathways involved. Description of the effects; Details on methods used in the study; Information on the results of the study.

Examines the effect of long-term treatment with insulin, 2,4-dinitrophenol (DNP) and mannitol on glucose transporter (GLUT) expression in L6 muscle cells and the signaling pathways involved. Experimental tools used; Mechanisms of insulin- and hypertonicity-mediated GLUT increases.

The efficacy and safety of stereotactic body radiation therapy (SBRT) for patients with nonspine bone metastases remains in question. A systematic review and meta-analysis were performed to evaluate SBRT treatment outcomes in nonspine bone metastases. Eligible studies were retrieved from MEDLINE, Embase, Scielo, the Cochrane Library, and annual meeting proceedings through July 6, 2023. We adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and Meta-analysis of Observational Studies in Epidemiology (MOOSE) guideline recommendations. Quantitative synthesis was performed using a random-effects model. Meta-regression was performed to determine correlation between clinical and treatment factors with the local failure (LF) and fracture rate. P values ≤.05 were deemed statistically significant. Seven retrospective studies, with a total of 807 patients (1048 lesions) treated with SBRT were included, with median follow-up ranging from 7.6 to 26.5 months. The most common SBRT sites were pelvis (39.2%), ribs (25.8%), femur (16.7%), and humerus/shoulder region (8.7%). At 1 year, the LF and fracture rate were 7% (95% CI, 5.5%-8.5%; I2 = 0; n = 75/1048) and 5.3% (95% CI, 3%-7.5%; I2 = 0; n = 65/1010). The 2-year cumulative LF incidence was 12.1% (95% CI, 10%-15.5%). The overall survival and progression-free survival at 1 year were 82% (95% CI, 75%-88%; I2 = 82%; n = 746/867) and 33.5% (95% CI, 26%-41%; I2 = 0%; n = 51/152), with a median of 20.2 months (95% CI, 10.9-49.1 months) and 8.3 months (95% CI, 6.3-10.3 months) for overall survival and progression-free survival, respectively. Meta-regression analysis revealed a significant relationship between planning target volume and fracture rate (P <.05). Ribs (2.5%) followed by the femur (1.9%; 95% CI, 0%-6.1%) were the most common fracture sites. The occurrence of pain flare, fatigue, and dermatitis were 7%, 5.4%, and 0.65%, respectively. Stereotactic body radiation proves both safety and efficacy for non-spine bone metastases, and although serious complications (grade 3) are rare, one case of grade 5 complication was reported. Careful consideration of target volume is crucial due to its link with a higher fracture risk. [ABSTRACT FROM AUTHOR]

Metabolic dysregulation is an early event in carcinogenesis. Here, we examined the expression of enzymes involved in de novo lipogenesis (ATP-citrate lyase: ACLY), glucose uptake (Glucose Transporter 1: GLUT1), and folate–glutamate metabolism (Prostate-Specific Membrane Antigen: PSMA) as potential biomarkers of risk for early prostate cancer progression. Patients who were managed initially on active surveillance with a Gleason score of 6 or a low-volume Gleason score of 7 (3 + 4) were accrued from a prostate cancer diagnostic assessment program. Patients were asked to donate their baseline diagnostic biopsy tissues and permit access to their clinical data. PSMA, GLUT1, and ACLY expression were examined with immunohistochemistry (IHC) in baseline biopsies, quantitated by Histologic Score for expression in benign and malignant glands, and compared with patient time remaining on active surveillance (time-on-AS). All three markers showed trends for elevated expression in malignant compared to benign glands, which was statistically significant for ACLY. On univariate analysis, increased PSMA and GLUT1 expression in malignant glands was associated with shorter time-on-AS (HR: 5.06, [CI 95%: 1.83–13.94] and HR: 2.44, [CI 95%: 1.10–5.44], respectively). Malignant ACLY and benign gland PSMA and GLUT1 expression showed non-significant trends for such association. On multivariate analysis, overexpression of PSMA in malignant glands was an independent predictor of early PC progression (p = 0.006). This work suggests that the expression of metabolic enzymes determined by IHC on baseline diagnostic prostate biopsies may have value as biomarkers of risk for rapid PC progression. PSMA may be an independent predictor of risk for progression and should be investigated further in systematic studies. [ABSTRACT FROM AUTHOR]

Radiotherapy is a non-invasive standard treatment for prostate cancer (PC). However, PC develops radio-resistance, highlighting a need for agents to improve radiotherapy response. Canagliflozin, an inhibitor of sodium-glucose co-transporter-2, is approved for use in diabetes and heart failure, but is also shown to inhibit PC growth. However, whether canagliflozin can improve radiotherapy response in PC remains unknown. Here, we show that well-tolerated doses of canagliflozin suppress proliferation and survival of androgen-sensitive and insensitive human PC cells and tumors and sensitize them to radiotherapy. Canagliflozin blocks mitochondrial respiration, promotes AMPK activity, inhibits the MAPK and mTOR-p70S6k/4EBP1 pathways, activates cell cycle checkpoints, and inhibits proliferation in part through HIF-1α suppression. Canagliflozin mediates transcriptional reprogramming of several metabolic and survival pathways known to be regulated by ETS and E2F family transcription factors. Genes downregulated by canagliflozin are associated with poor PC prognosis. This study lays the groundwork for clinical investigation of canagliflozin in PC prevention and treatment in combination with radiotherapy. The anti-diabetic drug canagliflozin promotes sensitivity to radiotherapy in prostate cancer by blocking mitochondrial respiration and repressing the mTORC1- HIF-1α pathway. [ABSTRACT FROM AUTHOR]

Introduction: Algorithms for the treatment of prostate cancer (PrCa) rely on risk grouping, and those who fall into low (LR) and favourable intermediate risk (FIR) categories have multiple options for treatment. High‐intensity focused ultrasound (HiFU) is a local treatment modality that uses ultrasound waves to ablate prostate cancer. In case of treatment failure, optimal salvage modality after HiFU remains unclear. Methods: Here, we describe a retrospective review of our regional cancer database for men who underwent salvage radiotherapy after failure of HiFU treatment for prostate cancer. Oncologic and toxicity outcomes of the men identified in our database are discussed. Results: We identified 14 men in our regional database who received salvage radiotherapy (70–74 Gy with or without androgen deprivation therapy (ADT) after primary HiFU, in the period of 2009–2017. No cases of any grade 3 or higher toxicity were observed. In our cohort, 50% (7/14) of patients developed secondary biochemical failure at a median follow‐up of 54 months post‐radiotherapy, with a mean time to biochemical failure of 39 months. We compare our data to other available reports to date consisting mostly of small, non‐randomized studies. Our biochemical control rates are noticeably lower compared with those reported by other studies but our length of follow‐up is longer, compared with other studies. Conclusion: The available data to date suggest that salvage radiotherapy after HiFU failure is well‐tolerated albeit with only modest efficacy. [ABSTRACT FROM AUTHOR]

Background Compounds of plant origin and food components have attracted scientific attention for use as agents for cancer prevention and treatment. Wine contains polyphenols that were shown to have anti-cancer and other health benefits. The survival pathways of Akt and extracellular signal-regulated kinase (Erk), and the tumor suppressor p53 are key modulators of cancer cell growth and survival. In this study, we examined the effects of wine on proliferation and survival of human Non-small cell lung cancer (NSCLC) cells and its effects on signaling events. Methods Human NSCLC adenocarcinoma A549 and H1299 cells were used. Cell proliferation was assessed by thymidine incorporation. Clonogenic assays were used to assess cell survival. Immunoblotting was used to examine total and phosphorylated levels of Akt, Erk and p53. Results In A549 cells red wine inhibited cell proliferation and reduced clonogenic survival at doses as low as 0.02%. Red wine significantly reduced basal and EGF-stimulated Akt and Erk phosphorylation while it increased the levels of total and phosphorylated p53 (Ser15). Control experiments indicated that the anti-proliferative effects of wine were not mediated by the associated contents of ethanol or the polyphenol resveratrol and were independent of glucose transport into cancer cells. White wine also inhibited clonogenic survival, albeit at a higher doses (0.5-2%), and reduced Akt phosphorylation. The effects of both red and white wine on Akt phosphorylation were also verified in H1299 cells. Conclusions Red wine inhibits proliferation of lung cancer cells and blocks clonogenic survival at low concentrations. This is associated with inhibition of basal and EGF-stimulated Akt and Erk signals and enhancement of total and phosphorylated levels of p53. White wine mediates similar effects albeit at higher concentrations. Our data suggest that wine may have considerable anti-tumour and chemoprevention properties in lung cancer and deserves further systematic investigation in animal models of lung cancer. [ABSTRACT FROM AUTHOR]

• 268 patients in 7 trials submitted to SBRT were analyzed. • With SBRT the pooled 1-year local control (LC) rate was 80%. • BEDGy10 and neoadjuvant chemotherapy were associated with LC. • The 1-year and 2-year Overall Survival (OS) rates were 74% and 55% respectively. • A linear relationship between OS and LC was observed. To evaluate the feasibility, efficacy and safety of stereotactic ablative radiotherapy (SABR) to the primary tumor and lymph nodes in patients with locally advanced non-small cell lung cancer (LA-NSCLC) who are ineligible for or refused concomitant chemoradiation. In accordance with the PRISMA and MOOSE guidelines, a systematic review with meta -analysis was conducted. The study included reports that assessed the outcomes of SABR treatment in patients with LA-NSCLC. Studies evaluating SBRT as a boost following primary radiotherapy were excluded. The primary outcomes measured were local control (LC) and overall survival (OS). The secondary endpoint was the incidence of severe toxicity (grades 3–5). A meta -regression analysis was performed to explore the relationship between LC, OS, and severe toxicity. The Biologically Effective Dose (BED) was analyzed as a continuous variable. Statistical significance was defined as a p-value < 0.05. A total of seven studies (3 prospective and 4 retrospective studies) involving 268 patients (SBRT to primary and lymph nodes) were included in the analysis. The pooled 1-year LC rate was 80 % (95 % CI: 63–94 %), and the factors significantly associated with LC were BEDGy10 (p = 0.005) and neoadjuvant chemotherapy (p = 0.005). The 1-year and 2-year OS rates were 74 % (95 % CI: 58–90 %) and 55 % (95 % CI: 34–76 %), respectively. Meta-regression analysis indicated a linear relationship between OS and LC, with a 0.7 % increase in OS for each 1 % improvement in LC (p = 0.005). The pooled rate of grade 3 acute toxicity was 5 % (95 % CI: 1–10 %), and the rate of grade 5 toxicity was 1.7 % (95 % CI: 0–3 %). Promising results (LC and OS) with limited toxicity (feasibility) using SABR in LA-NSCLC warrant further research, emphasizing the need for larger, well-designed trials for further validation of the approach. [ABSTRACT FROM AUTHOR]

Background: The sestrin family of stress-responsive genes (SESN1-3) are suggested to be involved in regulation of metabolism and aging through modulation of the AMPK-mTOR pathway. AMP-activated protein kinase (AMPK) is an effector of the tumour suppressor LKB1, which regulates energy homeostasis, cell polarity, and the cell cycle. SESN1/2 can interact directly with AMPK in response to stress to maintain genomic integrity and suppress tumorigenesis. Ionizing radiation (IR), a widely used cancer therapy, is known to increase sestrin expression, and acutely activate AMPK. However, the regulation of AMPK expression by sestrins in response to IR has not been studied in depth. Methods and Findings: Through immunoprecipitation we observed that SESN2 directly interacted with the AMPKα1β1γ1 trimer and its upstream regulator LKB1 in MCF7 breast cancer cells. SESN2 overexpression was achieved using a Flag-tagged SESN2 expression vector or a stably-integrated tetracycline-inducible system, which also increased AMPKα1 and AMPKβ1 subunit phosphorylation, and co-localized with phosphorylated AMPKα-Thr127 in the cytoplasm. Furthermore, enhanced SESN2 expression increased protein levels of LKB1 and AMPKα1β1γ1, as well as mRNA levels of LKB1, AMPKα1, and AMPKβ1. Treatment of MCF7 cells with IR elevated AMPK expression and activity, but this effect was attenuated in the presence of SESN2 siRNA. In addition, elevated SESN2 inhibited IR-induced mTOR signalling and sensitized MCF7 cells to IR through an AMPK-dependent mechanism. Conclusions: Our results suggest that in breast cancer cells SESN2 is associated with AMPK, it is involved in regulation of basal and IR-induced expression and activation of this enzyme, and it mediates sensitization of cancer cells to IR. [ABSTRACT FROM AUTHOR]

High risk prostate cancer (HR-PrCa) is a subset of localized PrCa with significant potential for morbidity and mortality associated with disease recurrence and metastasis. Radiotherapy combined with Androgen Deprivation Therapy has been the standard of care for many years in HR-PrCa. In recent years, dose escalation, hypo-fractionation and high precision delivery with immobilization and image-guidance have substantially changed the face of modern PrCa radiotherapy, improving treatment convenience and outcomes. Ultra-hypo-fractionated radiotherapy delivered with high precision in the form of stereotactic body radiation therapy (SBRT) combines delivery of high biologically equivalent dose radiotherapy with the convenience of a shorter treatment schedule, as well as the promise of similar efficacy and reduced toxicity compared to conventional radiotherapy. However, rigorous investigation of SBRT in HR-PrCa remains limited. Here, we review the changes in HR-PrCa radiotherapy through dose escalation, hypo- and ultra-hypo-fractionated radiotherapy boost treatments, and the radiobiological basis of these treatments. We focus on completed and on-going trials in this disease utilizing SBRT as a sole radiation modality or as boost therapy following pelvic radiation. [ABSTRACT FROM AUTHOR]

Introduction: Limited data establish the efficacy and safety of SBRT in the abdominopelvic (AP) space, where SBRT delivery is challenging due to the proximity of radiosensitive luminal gastrointestinal (GI) organs. The aim of this study was to assess clinical outcomes in patients with AP OM treated with SBRT.Methods: Eligible patients were those with OM (defined as metastases in ≤3 total sites) in the AP space (excluding liver) treated with SBRT. Descriptive statistics and Kaplan-Meier estimates of (LC), progression-free survival (PFS), overall survival (OS) and chemotherapy-free survival (CFS) were performed.Results: Fifty-one patients with 58 AP OM received SBRT between 2011 and 2015. Median follow-up was 21.9 months. All SBRT treatments were delivered in 5 fractions with a median dose of 35 Gy (25-40 Gy). Progression post-SBRT occurred in 38/51 patients (75%), with a median PFS of 4.9 months (95% CI: 2.5-7.5), and 2-year PFS of 29%. Rates of 2-and 4-year LC were 74% and 69%, respectively. Median OS was 42.6 months (95% CI: 31-55). Oligometastatic progression occurred in 21/38 patients, and of those, 48% (10/21) received further SBRT. Resulting 2- and 4-year CFS were 47% and 37%, respectively (median 15.1 months). Nineteen patients (37%) experienced a grade 1 or 2 acute toxicity. One grade 3 (acute) toxicity was observed. No grade 4 or 5 toxicities were detected.Conclusions: SBRT to AP OM was associated with sustained LC, excellent OS and minimal toxicity. The use of SBRT allowed for prolonged CFS and the salvage of limited-burden distant failures. [ABSTRACT FROM AUTHOR]

Aspirin, the pro-drug of salicylate, is associated with reduced incidence of death from cancers of the colon, lung and prostate and is commonly prescribed in combination with metformin in individuals with type 2 diabetes. Salicylate activates the AMPactivated protein kinase (AMPK) by binding at the A-769662 drug binding site on theAMPKß1-subunit, amechanism that is distinct from metformin which disrupts the adenylate charge of the cell. A hallmark of many cancers is high rates of fatty acid synthesis and AMPK inhibits this pathway through phosphorylation of acetyl-CoA carboxylase (ACC). It is currently unknown whether targeting the AMPK-ACC-lipogenic pathway using salicylate and/or metformin may be effective for inhibiting cancer cell survival. Salicylate suppresses clonogenic survival of prostate and lung cancer cells at therapeutic concentrations achievable following the ingestion of aspirin (<1.0 mM); effects not observed in prostate (PNT1A) and lung (MRC-5) epithelial cell lines. Salicylate concentrations of 1 mM increased the phosphorylation of ACC and suppressed de novo lipogenesis and these effects were enhanced with the addition of clinical concentrations of metformin (100 µM) and eliminated in mouse embryonic fibroblasts (MEFs) deficient in AMPK ß1. Supplementation of media with fatty acids and/or cholesterol reverses the suppressive effects of salicylate and metformin on cell survival indicating the inhibition of de novo lipogenesis is probably important. Preclinical studies evaluating the use of salicylate based drugs alone and in combination with metformin to inhibit de novo lipogenesis and the survival of prostate and lung cancers are warranted. [ABSTRACT FROM AUTHOR]

An abstract of the article "Expression of the glucose transporters GLUT1, GLUT3, GLUT4 and GLUT12 in human cancer cells," by Carly Barron, Evangelia Tsiani, and Theodoros Tsakiridis is presented.

Abstract: Purpose: To analyze the (i) expression of AMPK in a variety of epithelial cancer cells, (ii) regulation of AMPK subunit expression by ionizing radiation (IR) and (iii) impact of AMPK on signaling pathways regulating cell cycle and survival. Methods and materials: Human lung, prostate, and breast normal and cancer cells were treated with 0 or 8Gy IR and mRNA and protein levels of AMPK were evaluated by RT-PCR and immunoblotting 24 or 48h later. Untreated and radiated wild type (WT) and AMPKα−/− mouse embryonic fibroblasts (MEFs) were analyzed by immunoblotting using total- and phosphorylation-specific antibodies. Histone H2Ax was examined by fluorescence microscopy. The cell cycle and survival of WT and AMPKα−/− MEFs was also evaluated following 8Gy by IR. Results: AMPK subunits were found widely expressed in normal and cancer epithelial cells. IR increased subunit protein levels and stimulated gene transcription in cancer cells. AMPKα−/−-MEFs showed enhanced basal total levels of ATM and phosphorylation of its substrates histone H2Ax, but inhibited response of these markers and of checkpoint kinase Chk2 phosphorylation to IR. AMPKα−/−-MEFs showed increased basal levels of p53 and cyclin-dependent kinase inhibitors p21cip1, but lack of response of both genes to IR. These cells had increased basal levels and activation of the Akt-mTOR-p70S6K/4-EBP1 signalling pathway. IR increased Akt, p70S6K and 4-EBP1 phosphorylation in WT-MEFs, but this was reduced in AMPKα−/−-MEFs. AMPKα−/−-MEFs failed to arrest at the G2-M checkpoint after IR and showed a trend for radio-resistance in proliferation assays. Conclusions: AMPK is widely expressed in human normal and cancer epithelial cells and its gene transcription, protein levels, and enzymatic activity is stimulated by IR. Work with AMPKα knockout cells suggests that AMPK (i) may mediate a suppressive regulation on basal expression and activity of ATM and its downstream effector pathways Chk2/p53-p21cip1 and Akt-mTOR, (ii) facilitates the normal response of these pathways to IR and, (iii) mediates the IR-induced G2-M checkpoint. [Copyright &y& Elsevier]

Introduction: Earlier, we showed that in cancer cells, AMP-activated kinase (AMPK) participates in a signal transduction pathway involving ATM-AMPK-p53/p21cip1 which is activated by ionizing radiation (IR) to mediate G2-M arrest and enhanced cytotoxicity. We also observed that AMPK modulates ATM expression and activity and the IR response of the Akt-mTOR pathway. Since the ATM, AMPK and Akt pathways are key targets of novel radio-sensitizing therapeutics, we examined the chronic modultion of expression and activity of those pathways by IR alone in xenograft models of lung cancer. Methods: Immuno-compromised mice were grafted with human lung A549 and H1299 cells, were treated with a single fraction of 0 or 10 Gy, and left to grow for 8 weeks. Extracted tumors were subjected to lysis and immunoblotting or fixation and immunohistochemical analysis. Results: IR inhibited significantly xenograft growth and was associated with increased expression of Ataxia Telengiectasia Mutated (ATM) and enhanced phosphorylation of two ATM targets, H2Ax and checkpoint kinase Chk2. Irradiated tumours showed increased total AMPK levels and phosphorylation of AMPK and its substrate Acetyl-CoA Carboxylase (ACC). IR led to enhanced expression and phosphorylation of p53 and cyclin dependent kinase inhibitors p21cip1 and p27kip1. However, irradiated tumours had reduced phosphorylation of Akt, mTOR and it's target translation initiation inhibitor 4EBP1. Irradiated xenografts showed reduced microvessel density, reduced expression of CD31 but increased expression of hypoxia-induced factor 1A (HIF1a) compared to controls. Conclusion: IR inhibits epithelial cancer tumour growth and results in sustained expression and activation of ATM-Chk2, and AMPK-p53/p21cip1/p27kip1 but partial inhibition of the Akt-mTOR signaling pathways. Future studies should examine causality between those events and explore whether further modulation of the AMPK and Akt-mTOR pathways by novel therapeutics can sensitize lung tumours to radiation. [ABSTRACT FROM AUTHOR]

Background: Mammary carcinomas have been associated with a high-fat diet, and the rate of breast cancer in overweight post-menopausal women is up to 50% higher than in their normal-weight counterparts. Epidemiological studies suggest that prolactin (PRL) plays a role in the progression of breast cancer. The current study examined breast cancer as a metabolic disease in the context of altered fatty acid catabolism by examining the effect of PRL on carnitine palmitoyl transferase 1 (CPT1), an enzyme that shuttles long-chain fatty acids into the mitochondrial matrix for b-oxidation. The effect of PRL on the adenosine 5'-monophosphate-activated protein kinase (AMPK) energy sensing pathway was also investigated. Methods: MCF-7 and MDA-MB-231 breast cancer cells and 184B5 normal breast epithelial cells treated with 100 ng/ml of PRL for 24 hr were used as in vitro models. Real-time PCR was employed to quantify changes in mRNA levels and Western blotting was carried out to evaluate changes at the protein level. A non-radioactive CPT1 enzyme activity assay was established and siRNA transfections were performed to transiently knock down specific targets in the AMPK pathway. Results: PRL stimulation increased the expression of CPT1A (liver isoform) at the mRNA and protein levels in both breast cancer cell lines, but not in 184B5 cells. In response to PRL, a 20% increase in CPT1 enzyme activity was observed in MDA-MB-231 cells. PRL treatment resulted in increased phosphorylation of the a catalytic subunit of AMPK at Thr172, as well as phosphorylation of acetyl-CoA carboxylase (ACC) at Ser79. A siRNA against liver kinase B1 (LKB1) reversed these effects in breast cancer cells. PRL partially restored CPT1 activity in breast cancer cells in which CPT1A, LKB1, or AMPKa-1 were knocked down. Conclusions: PRL enhances fatty acid β-oxidation by stimulating CPT1 expression and/or activity in MCF-7 and MDA-MB-231 breast cancer cells. These PRL-mediated effects are partially dependent on the LKB1-AMPK pathway, although the regulation of CPT1 is also likely to be influenced by other mechanisms. Ultimately, increased CPT1 enzyme activity may contribute to fueling the high energy demands of cancer cells. Targeting metabolic pathways that are governed by PRL, which has already been implicated in the progression of breast cancer, may be of therapeutic benefit. [ABSTRACT FROM AUTHOR]

Purpose: Adenosine monophosphate (AMP)–activated kinase (AMPK) is a molecular energy sensor regulated by the tumor suppressor LKB1. Starvation and growth factors activate AMPK through the DNA damage sensor ataxia-telangiectasia mutated (ATM). We explored the regulation of AMPK by ionizing radiation (IR) and its role as a target for radiosensitization of human cancer cells. Methods and Materials: Lung, prostate, and breast cancer cells were treated with IR (2–8 Gy) after incubation with either ATM or AMPK inhibitors or the AMPK activator metformin. Then, cells were subjected to either lysis and immunoblotting, immunofluorescence microscopy, clonogenic survival assays, or cell cycle analysis. Results: IR induced a robust phosphorylation and activation of AMPK in all tumor cells, independent of LKB1. IR activated AMPK first in the nucleus, and this extended later into cytoplasm. The ATM inhibitor KU-55933 blocked IR activation of AMPK. AMPK inhibition with Compound C or anti–AMPK α subunit small interfering RNA (siRNA) blocked IR induction of the cell cycle regulators p53 and p21waf/cip as well as the IR-induced G2/M arrest. Compound C caused resistance to IR, increasing the surviving fraction after 2 Gy, but the anti-diabetic drug metformin enhanced IR activation of AMPK and lowered the surviving fraction after 2 Gy further. Conclusions: We provide evidence that IR activates AMPK in human cancer cells in an LKB1-independent manner, leading to induction of p21waf/cip and regulation of the cell cycle and survival. AMPK appears to (1) participate in an ATM–AMPK–p21waf/cip pathway, (2) be involved in regulation of the IR-induced G2/M checkpoint, and (3) may be targeted by metformin to enhance IR responses. [ABSTRACT FROM AUTHOR]

Background: Mammary carcinomas have been associated with a high-fat diet, and the rate of breast cancer in overweight post-menopausal women is up to 50% higher than in their normal-weight counterparts. Epidemiological studies suggest that prolactin (PRL) plays a role in the progression of breast cancer. The current study examined breast cancer as a metabolic disease in the context of altered fatty acid catabolism by examining the effect of PRL on carnitine palmitoyl transferase 1 (CPT1), an enzyme that shuttles long-chain fatty acids into the mitochondrial matrix for β-oxidation. The effect of PRL on the adenosine 5'-monophosphate-activated protein kinase (AMPK) energy sensing pathway was also investigated.Methods: MCF-7 and MDA-MB-231 breast cancer cells and 184B5 normal breast epithelial cells treated with 100 ng/ml of PRL for 24 hr were used as in vitro models. Real-time PCR was employed to quantify changes in mRNA levels and Western blotting was carried out to evaluate changes at the protein level. A non-radioactive CPT1 enzyme activity assay was established and siRNA transfections were performed to transiently knock down specific targets in the AMPK pathway.Results: PRL stimulation increased the expression of CPT1A (liver isoform) at the mRNA and protein levels in both breast cancer cell lines, but not in 184B5 cells. In response to PRL, a 20% increase in CPT1 enzyme activity was observed in MDA-MB-231 cells. PRL treatment resulted in increased phosphorylation of the α catalytic subunit of AMPK at Thr172, as well as phosphorylation of acetyl-CoA carboxylase (ACC) at Ser79. A siRNA against liver kinase B1 (LKB1) reversed these effects in breast cancer cells. PRL partially restored CPT1 activity in breast cancer cells in which CPT1A, LKB1, or AMPKα-1 were knocked down.Conclusions: PRL enhances fatty acid β-oxidation by stimulating CPT1 expression and/or activity in MCF-7 and MDA-MB-231 breast cancer cells. These PRL-mediated effects are partially dependent on the LKB1-AMPK pathway, although the regulation of CPT1 is also likely to be influenced by other mechanisms. Ultimately, increased CPT1 enzyme activity may contribute to fueling the high energy demands of cancer cells. Targeting metabolic pathways that are governed by PRL, which has already been implicated in the progression of breast cancer, may be of therapeutic benefit. [ABSTRACT FROM AUTHOR]