Interplay between sirtuins, MYC and hypoxia-inducible factor in cancer-associated metabolic reprogramming

In the early twentieth century, Otto Heinrich Warburg described an elevated rate of glycolysis occurring in cancer cells, even in the presence of atmospheric oxygen (the Warburg effect). Despite the inefficiency of ATP generation through glycolysis, the breakdown of glucose into lactate provides cancer cells with a number of advantages, including the ability to withstand fluctuations in oxygen levels, and the production of intermediates that serve as building blocks to support rapid proliferation. Recent evidence from many cancer types supports the notion that pervasive metabolic reprogramming in cancer and stromal cells is a crucial feature of neoplastic transformation. Two key transcription factors that play major roles in this metabolic reprogramming are hypoxia inducible factor-1 (HIF1) and MYC. Sirtuin-family deacetylases regulate diverse biological processes, including many aspects of tumor biology. Recently, the sirtuin SIRT6 has been shown to inhibit the transcriptional output of both HIF1 and MYC, and to function as a tumor suppressor. In this Review, we highlight the importance of HIF1 and MYC in regulating tumor metabolism and their regulation by sirtuins, with a main focus on SIRT6

SIRT3: as simple as it seems?

Identification of conserved pathways regulating longevity holds out the eventual possibility of pharmacologic health- and lifespan extension in humans. Members of the sirtuin deacetylase/ADP-ribosyltransferase/deacylase family extend longevity in invertebrates and promote various aspects of mammalian healthspan. The mitochondrial sirtuin SIRT3 deacetylates numerous proteins in this organelle, regulating mitochondrial functions and suppressing diverse age-associated pathologies. However, recent findings raise the possibility that SIRT3 may regulate some mitochondrial functions indirectly, rather than by direct deacetylation of specific mitochondrial substrates. Specifically, it has been found that SIRT3 promotes activities of the upstream mitochondrial regulators adenosine monophosphate-activated protein kinase and PGC1α. In addition, studies of tissue-specific SIRT3 knockouts suggest non-tissue-autonomous roles for SIRT3. Thus, mitochondrial regulation by SIRT3 is likely much more complex than initially appreciated, potentially involving both direct and indirect mechanisms. Unraveling these may reveal novel aspects of how the functional status of the mitochondria is communicated to the rest of the cell, and to the organism overall

Altered Angiogenic Growth Factors in Urine of Prostate Cancer Survivors With Radiation History and Radiation Cystitis

© 2018 Elsevier Inc. Objective: To determine if the vascular damage in bladders of prostate cancer (PCa) survivors with radiation cystitis can be detected through altered angiogenic growth factors in urine. Methods: Urine samples from PCa survivors with a history of external beam radiation therapy were tested for a panel of angiogenic growth factors by Luminex assay. Urine creatinine levels were measured through high performance liquid chromatography. Through a patient survey, data on patient demographics, radiation history, and urinary symptoms were collected. Results: Hepatocyte growth factor (HGF), placental growth factor (PlGF), and vascular endothelial growth factor (VEGF) were altered in urine of PCa survivors with a history of radiation therapy. HGF and PlGF were elevated in response to irradiation, while VEGF had a decreasing trend. Within the irradiated population, HGF was also increased in patients diagnosed with radiation cystitis and patients with hematuria. PlGF and VEGF

Prostate cancer survivors with symptoms of radiation cystitis have elevated fibrotic and vascular proteins in urine.

Radiation for pelvic cancers can result in severe bladder damage and radiation cystitis (RC), which is characterized by chronic inflammation, fibrosis, and vascular damage. RC development is poorly understood because bladder biopsies are difficult to obtain. The goal of this study is to gain understanding of molecular changes that drive radiation-induced cystitis in cancer survivors using urine samples from prostate cancer survivors with history of radiation therapy. 94 urine samples were collected from prostate cancer survivors with (n = 85) and without (n = 9) history of radiation therapy. 15 patients with radiation history were officially diagnosed with radiation cystitis. Levels of 47 different proteins were measured using Multiplex Luminex. Comparisons were made between non-irradiated and irradiated samples, and within irradiated samples based on radiation cystitis diagnosis, symptom scores or hematuria. Statistical analysis was performed using Welch's t-test. In prostate cancer survivors with history of radiation therapy, elevated levels of PAI 1, TIMP1, TIMP2, HGF and VEGF-A were detected in patients that received a radiation cystitis diagnosis. These proteins were also increased in patients suffering from hematuria or high symptom scores. No inflammatory proteins were detected in the urine, except in patients with gross hematuria and end stage radiation cystitis. Active fibrosis and vascular distress is detectable in the urine through elevated levels of associated proteins. Inflammation is only detected in urine of patients with end-stage radiation cystitis disease. These results suggest that fibrosis and vascular damage drive the development of radiation cystitis and could lead to the development of more targeted treatments

Identification of Molecular Mechanisms in Radiation Cystitis: Insights from RNA Sequencing

Pelvic cancer survivors who were treated with radiation therapy are at risk for developing (hemorrhagic) radiation cystitis (RC) many years after completion of radiation therapy. Patients with RC suffer from lower urinary tract symptoms, including frequency, nocturia, pelvic pain, and incontinence. In advanced stages, hematuria can occur, potentially escalating to life-threatening levels. Current therapeutic options for RC are limited, partly due to ethical concerns regarding bladder biopsy in patients with fragile bladder tissue. This study aimed to leverage our established preclinical model to elucidate the molecular pathways implicated in radiation-induced tissue changes in the bladder. Female C57Bl/6 mice received a single dose of 40 Gy using CT-guided imaging and a two-beam irradiation approach using the SARRP irradiator. Bladders from irradiated and age-matched littermate controls were harvested at 1 week [n = 5/group] or 6 months [n = 5/group] after irradiation, RNA was harvested, and mRNA sequencing was performed at paired-end 150bp on the Illumina NovaSeq6000 with a target of 30 million reads per sample. Following RNA sequencing, thorough bioinformatics analysis was performed using iPathwayGuide v2012 (ADVAITA Bioinformatics). Findings of the RNA sequencing were validated using qPCR analysis. At 1 week post-irradiation, altered gene expression was detected in genes involved in DNA damage response, apoptosis, and transcriptional regulation. By 6 months post-irradiation, significant changes in gene expression were observed in inflammation, collagen catabolism, and vascular health. Affected pathways included the p53, JAK-STAT, and PI3K-Akt pathways. These findings were validated in vivo in bladder tissues from our preclinical model. This is the first study to determine the molecular changes in the bladder in response to radiation treatment. We have successfully pinpointed several pathways and specific genes that undergo modification, thereby contributing to the progression of radiation cystitis. These insights enhance our understanding of the pathophysiology of radiation cystitis and may ultimately pave the way to the identification of potential new therapeutic targets