Gemcitabine kills proliferating endothelial cells exclusively via acid sphingomyelinase activation

Evofosfamide and Gemcitabine Act Synergistically in Pancreatic Cancer Xenografts by Dual Action on Tumor Vasculature and Inhibition of Homologous Recombination DNA Repair

Aims: Pancreatic ductal adenocarcinomas (PDACs) form hypovascular and hypoxic tumors, which are difficult to treat with current chemotherapy regimens. Gemcitabine (GEM) is often used as a first-line treatment for PDACs but has issues with chemoresistance and penetration in the interior of the tumor. Evofosfamide, a hypoxia-activated prodrug, has been shown to be effective in combination with GEM, although the mechanism of each drug on the other has not been established. We used mouse xenografts from two cell lines (MIA Paca-2 and SU.86.86) with different tumor microenvironmental characteristics to probe the action of each drug on the other. Results: GEM treatment enhanced survival times in mice with SU.86.86 leg xenografts (hazard ratio [HR] = 0.35, p = 0.03) but had no effect on MIA Paca-2 mice (HR = 0.91, 95% confidence interval = 0.37-2.25, p = 0.84). Conversely, evofosfamide did not improve survival times in SU.86.86 mice to a statistically significant degree (HR = 0.57, p = 0.22). Electron paramagnetic resonance imaging showed that oxygenation worsened in MIA Paca-2 tumors when treated with GEM, providing a direct mechanism for the activation of the hypoxia-activated prodrug evofosfamide by GEM. Sublethal amounts of either treatment enhanced the toxicity of other treatment in vitro in SU.86.86 but not in MIA Paca-2. By the biomarker γH2AX, combination treatment increased the number of double-stranded DNA lesions in vitro for SU.86.86 but not MIA Paca-2. Innovation and Conclusion: The synergy between GEM and evofosfamide appears to stem from the dual action of GEMs effect on tumor vasculature and inhibition by GEM of the homologous recombination DNA repair process. Antioxid. Redox Signal. 39, 432-444.

Hyperlipidemia as a risk factor for Trousseau syndrome‑related cerebral infarction in patients with advanced gastrointestinal cancer

Trousseau syndrome-related cerebral infarction rarely occurs during chemotherapy in patients with gastrointestinal (GI) cancer, and its clinical features remain unclear. The present study aimed to examine the clinical features of Trousseau syndrome-related cerebral infarction developed during chemotherapy for GI cancer. The present retrospective cohort study consecutively enrolled 878 patients with unresectable GI cancer who received chemotherapy at the Multidisciplinary Treatment Cancer Center, Kurume University Hospital (Kurume, Japan) between April 2014 and March 2020. Patients with colorectal cancer (n=308) were the most common, followed by those with pancreatic (n=242), gastric (n=222) and biliary tract (n=59) cancer, neuroendocrine tumors (n=34) and duodenal cancer (n=11). Among the 878 patients, Trousseau syndrome-related cerebral infarction occurred in 8 (0.9%) patients with a median age of 70.5 years (range, 58–75 years), and 50% of the patients were male (4/8). In total, 3 patients had gastric cancer, 3 had pancreatic cancer and 2 had biliary tract cancer. A greater percentage of patients with Trousseau syndrome-related cerebral infarction had hyperlipidemia (38.0%) than those without (8.2%; P=0.005). Hyperlipidemia was a risk factor for occurrence of Trousseau syndrome-related cerebral infarction with an odds ratio of 7.009 (95% confidence interval, 1.785-27.513). Trousseau syndrome-related cerebral infarction developed during GI chemotherapy was rare and hyperlipidemia may predict its onset.

Chemotherapy-induced acute vascular injury involves intracellular generation of ROS via activation of the acid sphingomyelinase pathway

Several categories of chemotherapy confer substantial risk for late-term vascular morbidity and mortality. In the present study, we aimed to investigate the mechanism of acute chemotherapy-induced vascular injury in normal tissues. Specifically, we looked at activation of the acid sphingomyelinase (ASMase)/ceramide pathway, which leads to generation of reactive oxygen species (ROS) and induction of oxidative stress that may result in vascular injury. In particular, we focused on two distinct drugs, doxorubicin (DOX) and cisplatin (CIS) and their effects on normal endothelial cells. In vitro, DOX resulted in increased ASMase activity, intra-cellular ROS production and induction of apoptosis. CIS treatment generated significantly reduced effects in endothelial cells. In-vivo, murine femoral arterial blood flow was measured in real-time, during and after DOX or CIS administration, using fluorescence optical imaging system. While DOX caused constriction of small vessels and disintegration of large vessels' wall, CIS induced minor vascular changes in arterial blood flow, correlating with the in vitro findings. These results demonstrate that DOX induces acute vascular injury by increased ROS production, via activation of ASMase/ceramide pathway, while CIS increases ROS production and its immediate extracellular translocation, without causing detectable acute vascular injury. Our findings may potentially lead to the development of new strategies to prevent long-term cardiovascular morbidity in cancer survivors.

Acid sphingomyelinase-dependent autophagic degradation of GPX4 is critical for the execution of ferroptosis

Ferroptosis is a type of regulated cell death characterized by ROS accumulation and devastating lipid peroxidation (LPO). The role of acid sphingomyelinase (ASM), a key enzyme in sphingolipid metabolism, in the induction of apoptosis has been studied; however, to date its role in ferroptosis is unclear. In this study, we report that ASM plays a hitherto unanticipated role in promoting ferroptosis. Mechanistically, Erastin (Era) treatment results in the activation of ASM and generation of ceramide, which are required for the Era-induced reactive oxygen species (ROS) generation and LPO. Inhibition of nicotinamide adenine dinucleotide phosphate oxidase (NADPH oxidase) or removal of intracellular ROS, significantly reduced Era-induced ASM activation, suggesting that NADPH oxidase-derived ROS regulated ASM-initiated redox signaling in a positive feedback manner. Moreover, ASM-mediated activation of autophagy plays a critical role in ferroptosis inducers (FINs)-induced glutathione peroxidase 4 (GPX4) degradation and ferroptosis activation. Genetic or pharmacological inhibition of ASM diminishes Era-induced features of autophagy, GPX4 degradation, LPO, and subsequent ferroptosis. Importantly, genetic activation of ASM increases ferroptosis in cancer cells induced by various FINs. Collectively, these findings reveal that ASM plays a novel role in ferroptosis that could be exploited to improve pathological conditions that link to ferroptosis.

Lipid-Iron Nanoparticle with a Cell Stress Release Mechanism Combined with a Local Alternating Magnetic Field Enables Site-Activated Drug Release

Most available cancer chemotherapies are based on systemically administered small organic molecules, and only a tiny fraction of the drug reaches the disease site. The approach causes significant side effects and limits the outcome of the therapy. Targeted drug delivery provides an alternative to improve the situation. However, due to the poor release characteristics of the delivery systems, limitations remain. This report presents a new approach to address the challenges using two fundamentally different mechanisms to trigger the release from the liposomal carrier. We use an endogenous disease marker, an enzyme, combined with an externally applied magnetic field, to open the delivery system at the correct time only in the disease site. This site-activated release system is a novel two-switch nanomachine that can be regulated by a cell stress-induced enzyme at the cellular level and be remotely controlled using an applied magnetic field. We tested the concept using sphingomyelin-containing liposomes encapsulated with indocyanine green, fluorescent marker, or the anticancer drug cisplatin. We engineered the liposomes by adding paramagnetic beads to act as a receiver of outside magnetic energy. The developed multifunctional liposomes were characterized in vitro in leakage studies and cell internalization studies. The release system was further studied in vivo in imaging and therapy trials using a squamous cell carcinoma tumor in the mouse as a disease model. In vitro studies showed an increased release of loaded material when stress-related enzyme and magnetic field was applied to the carrier liposomes. The theranostic liposomes were found in tumors, and the improved therapeutic effect was shown in the survival studies.

Chemotherapeutic Agents-Induced Ceramide-Rich Platforms (CRPs) in Endothelial Cells and Their Modulation

The prevailing mechanism of action of chemotherapeutic drugs has been challenged by the role of ceramide, a second messenger, shown to induce apoptosis, differentiation, growth arrest, senescence, and autophagy in different cells (Chabner BA, Roberts TG Jr, Nat Rev Cancer 5:65-72, 2005; Jacobi J et al, Cell Signal 29:52-61, 2017; Rotolo J et al, J Clin Invest 122:1786-1790, 2012; Truman JP et al, PLoS One 5:e12310, 2010). Certain chemotherapeutic drugs activate the acid sphingomyelinase (ASMase)/ceramide pathway, generating ceramide in the tumor endothelium and this microvascular dysfunction is crucial for the tumor response. Ceramide has fusigenic properties and as such, when generated within the plasma membrane, initiates the oligomerization of ceramide-and cholesterol-rich domains in the outer leaflet of the plasma membrane, leading to the formation of ceramide-rich microdomains/platforms (CRP) (Jacobi J et al, Cell Signal 29:52-61, 2017; Truman JP et al, PLoS One 5:e12310, 2010; van Hell AJ et al, Cell Signal 34:86-91, 2017; Hajj C, Haimovitz-Friedman A, Handb Exp Pharmacol 216:115-130, 2013) known as "signaling platform." This chapter will discuss the generation, detection, and quantitation of CRP and their possible modulation in endothelial cells, in vitro and in vivo in response to certain chemotherapeutic drugs.

Enhancement of Soft Tissue Sarcoma Response to Gemcitabine through Timed Administration of a Short-Acting Anti-Angiogenic Agent

BACKGROUND/AIMS

Despite enormous effort, anti-angiogenic drugs have not lived up to the promise of globally-enhancing anti-cancer therapies. Clinically, anti-angiogenic drugs have been used to persistently suppress vascular endothelial growth factor (VEGF) in order to "normalize" dysfunctional neo-angiogenic microvasculature and prevent recruitment of endothelial progenitors. Recently, we showed that a 1h pre-treatment with anti-angiogenic drugs prior to ultra-high single dose radiotherapy and specific chemotherapies transiently de-represses acid sphingomyelinase (ASMase), leading to enhanced cancer therapy-induced, ceramide-mediated vascular injury and tumor response. Here we formally decipher parameters of chemotherapy induction of endothelial sphingolipid signaling events and define principles for optimizing anti-angiogenic chemosensitization.

METHODS

These studies examine the antimetabolite chemotherapeutic gemcitabine in soft tissue sarcoma (STS), a clinically-relevant combination.

RESULTS

Initial studies address the theoretic problem that anti-angiogenic drugs such as bevacizumab, an IgG with a 3-week half-life, have the potential for accumulating during the 3-week chemotherapeutic cycles currently standard-of-care for STS treatment. We show that anti-angiogenic ASMase-dependent enhancement of the response of MCA/129 fibrosarcomas in sv129/BL6 mice to gemcitabine progressively diminishes as the level of the VEGFR2 inhibitor DC101, an IgG, accumulates, suggesting a short-acting anti-angiogenic drug might be preferable in multi-cycle chemotherapeutic regimens. Further, we show lenvatinib, a VEGFR2 tyrosine kinase inhibitor with a short half-life, to be superior to DC101, enhancing gemcitabine-induced endothelial cell apoptosis and tumor response in a multi-cycle treatment schedule.

CONCLUSION

We posit that a single delivery of a short-acting anti-angiogenic agent at 1h preceding each dose of gemcitabine and other chemotherapies may be more efficacious for repeated sensitization of the ASMase pathway in multi-cycle chemotherapy regimens than current treatment strategies.

Fusion of lysosomes to plasma membrane initiates radiation-induced apoptosis

Diverse stresses, including reactive oxygen species (ROS), ionizing radiation, and chemotherapies, activate acid sphingomyelinase (ASMase) and generate the second messenger ceramide at plasma membranes, triggering apoptosis in specific cells, such as hematopoietic cells and endothelium. Ceramide elevation drives local bilayer reorganization into ceramide-rich platforms, macrodomains (0.5-5-µm diameter) that transmit apoptotic signals. An unresolved issue is how ASMase residing within lysosomes is released extracellularly within seconds to hydrolyze sphingomyelin preferentially enriched in outer plasma membranes. Here we show that physical damage by ionizing radiation and ROS induces full-thickness membrane disruption that allows local calcium influx, membrane lysosome fusion, and ASMase release. Further, electron microscopy reveals that plasma membrane "nanopore-like" structures (∼100-nm diameter) form rapidly due to lipid peroxidation, allowing calcium entry to initiate lysosome fusion. We posit that the extent of upstream damage to mammalian plasma membranes, calibrated by severity of nanopore-mediated local calcium influx for lysosome fusion, represents a biophysical mechanism for cell death induction.

Exploring the Therapeutic Landscape of Sphingomyelinases

Sphingosine, ceramide, sphingosine-1-phosphate, and other related sphingolipids have emerged as important bioactive molecules involved in a variety of key cellular processes such as cell growth, differentiation, apoptosis, exosome release, and inter- and intracellular cell communication, making the pathways of sphingolipid metabolism a key domain in maintaining cell homeostasis (Hannun and Obeid, Trends Biochem Sci 20:73-77, 1995; Hannun and Obeid, Nat Rev Mol Cell Biol 9:139-150, 2008; Kosaka et al., J Biol Chem 288:10849-10859, 2013). Various studies have determined that these pathways play a central role in regulating intracellular production of ceramide and the other bioactive sphingolipids and hence are an important component of signaling in various diseases such as cancer, diabetes, and neurodegenerative and cardiovascular diseases (Chaube et al., Biochim Biophys Acta 1821:313-323, 2012; Clarke et al., Adv Enzyme Regul 51:51-58, 2011b; Horres and Hannun, Neurochem Res 37:1137-1149, 2012). In this chapter, we discuss one of the major enzyme classes in producing ceramide, sphingomyelinases (SMases), from a biochemical and structural perspective with an emphasis on their applicability as therapeutic targets.

Hypertension in Cancer Patients and Survivors: Epidemiology, Diagnosis, and Management

Cancer patients and survivors of cancer have a greater burden of cardiovascular disease compared to the general population. Much of the elevated cardiovascular risk in these individuals is likely attributable to hypertension, as individuals with cancer have a particularly high incidence of hypertension following cancer diagnosis. Treatment with chemotherapy is an independent risk factor for hypertension due to direct effects of many agents on endothelial function, sympathetic activity, and renin-angiotensin system activity as well as nephrotoxicity. Diagnosis and management of hypertension in cancer patients requires accurate blood pressure measurement and consideration of potential confounding factors, such as adjuvant treatments and acute pain, that can temporarily elevate blood pressure readings. Home blood pressure monitoring can be a useful tool to facilitate longitudinal blood pressure monitoring for titration of antihypertensive medications. Selection of antihypertensive agents in cancer patients should account for treatment-specific morbidities and target organ injury.

Encapsulating fibrosis following neoadjuvant chemotherapy is correlated with outcomes in patients with pancreatic cancer

Pathological assessments of the treatment effect are critical for predicting patient outcomes after surgery. This study included 82 localized pancreatic cancer, 40 of whom were treated with neoadjuvant therapy (NAT) using four courses of gemcitabine plus nab-paclitaxel (GnP) followed by pancreatectomy (GnP group). The remaining 42 patients were treated with upfront pancreatectomy (UP) followed by adjuvant chemotherapy (UP group). We reviewed clinicopathological data of these patients to assess differences between the GnP and UP groups and further evaluate the prognostic impact of residual tumors after GnP treatment. Adjuvant treatment (S1, GnP or gemcitabine) was administered for 36 patients in the GnP group and 33 patients in the UP group. Compared to the UP group, the GnP group showed lower serum CA19-9 levels, microscopic tumor volume, and tumor-stroma ratio and decreased number of lymph node metastasis and vascular invasion. Higher incidence of encapsulating fibrosis was observed in the GnP group than in the UP group. Relative to the UP group (69%), a higher R0 rate was observed in the GnP group (85%). As for prognosis, encapsulating fibrosis was correlated with the overall survival of patients in the GnP group. However, overall survival did not show any correlation with other clinicopathological factors, including tumor reduction ratio (determined by computed tomography) and tumor regression grade (determined following criteria of Evans’ grading system or those of the College of American Pathologists). In conclusion, the present study revealed that GnP-induced encapsulating fibrosis could predict patients’ outcome. Nevertheless, large cohort studies are warranted to further evaluate the prognostic value of fibrosis, possibly with the help of imaging and biomarkers.

Tricyclic antidepressant amitriptyline inhibits autophagic flux and prevents tube formation in vascular endothelial cells

Amitriptyline is a tricyclic antidepressant and an inhibitor of lysosomal acid sphingomyelinase (ASM). Amitriptyline is well known for its cardiovascular side effects and toxicity in psychiatric patients. However, the mechanisms underlying the cardiovascular side effects of amitriptyline remain largely undefined. This study aimed to determine the effects of amitriptyline on angiogenic capability of vascular endothelial cells in physiological settings and identify its mechanism of action. The ex vivo aortic ring angiogenesis and in vitro-cultured endothelial cell tube formation assay were used to assess the effects of amitriptyline on endothelial angiogenic capability. It was demonstrated that amitriptyline impaired the angiogenesis of aortic rings, which was similar to that found in aortic rings with haploinsufficiency of the ASM gene. In cultured mouse microvascular endothelial cells (MVECs), amitriptyline impaired the proliferation and tube formation under basal condition, which were accompanied by attenuated angiogenic signalling pathways such as endothelial nitric oxide synthase, Akt and Erk1/2 pathways. Mechanistically, amitriptyline inhibited autophagic flux without affecting autophagosome biogenesis at basal condition. ASM gene silencing or autophagy inhibition mimics the inhibitory effects of amitriptyline on endothelial cell proliferation and tube formation. Collectively, our data suggest that amitriptyline inhibits endothelial cell proliferation and angiogenesis via blockade of ASM-autophagic flux axis. It is implicated that the cardiovascular side effects of amitriptyline may be associated with its inhibitory action on physiological angiogenesis.