Selective Induction of Cellular Toxicity and Anti-tumor Efficacy by N-Methylpiperazinyl Diarylidenylpiperidone and its Pro-nitroxide Conjugate through ROS-mediated Mitochondrial Dysfunction and G2/M Cell-cycle Arrest in Human Pancreatic Cancer.

Pancreatic adenocarcinoma is an aggressive cancer with poor clinical prognosis and limited therapeutic options. There is a significant lack of effective, safe, and targeted therapies for successful treatment of pancreatic cancer. In this report, we describe the anticancer efficacy of two novel compounds, N-methylpiperazinyl diarylidenylpiperidone (L-2663) and its pro-nitroxide conjugate (HO-4589) evaluated on human pancreatic adenocarcinoma (AsPC-1) cell line and xenograft tumor in mice. Using flow cytometry, we determined the effect of the L-2663 and HO-4589 drugs in inducing mitochondrial toxicity, triggering cell-cycle arrest, and apoptosis. EPR spectroscopy was used to quantify cellular uptake, metabolic conversion and stability of HO-4589 in cells and in vivo monitoring of tumor oxygenation as a function of growth. The results established different antiproliferative efficacy of the L-2663 and HO-4589 compounds, with a targeted action on cancer cells while being less toxic to noncancerous cells. The study may have important implications in the future designs of safe and effective chemotherapeutic agents for the treatment of pancreatic cancer.

Estimation of pO2 histogram from a composite EPR Spectrum of multiple random implants.

Electron paramagnetic resonance (EPR) spectroscopy using oxygen-sensing implants can provide reliable and repeated measurements of the partial pressure of oxygen (pO2) over a period of months or longer; however, it does not provide accurate information about the distribution of tissue oxygenation. While EPR imaging has the capability to provide spatially resolved oxygen data, it is time-consuming and not optimized for discrete number of implants. Previous reports suggest multi-site algorithms, which would require either the implants to be aligned in a certain way so as to deconvolve them using a linear magnetic field gradient or sparse imaging of the implants from a small number of 3D projections. In this paper, we present a simpler and much faster method to estimate the pO2 histogram from a composite, single-scan EPR spectrum measured without applying field gradients to separate the EPR signals from multiple randomly placed oxygen-sensing implants. The method is optimized for a discrete number of implants, validated using simulations, experimental phantoms and in animal models. The results established the composite spectral fitting algorithm as a reliable and robust tool for multi-site oximetry.

Implantable microchip containing oxygen-sensing paramagnetic crystals for long-term, repeated, and multisite in vivo oximetry.

EPR oximetry is established as a viable method for measuring the tissue oxygen level (partial pressure of oxygen, pO2) in animal models; however, it has not yet been established for measurements in humans. EPR oximetry requires an oxygen-sensing paramagnetic probe (molecular or particulate) to be placed at the site/organ of measurement, which may pose logistical and safety concerns, including invasiveness of the probe-placement procedure as well as lack of temporal stability and sensitivity for long-term (repeated) measurements, and possible toxicity in the short- and long-term. In the past, we have developed an implantable oxygen-sensing probe, called OxyChip, which we have successfully established for oximetry in pre-clinical animal models (Hou et al. Biomed. Microdevices 20, 29, 2018). Currently, OxyChip is being evaluated in a limited clinical trial in cancer patients. A major limitation of OxyChip is that it is a large (1.4 mm3) implant and hence not suitable for measuring oxygen heterogeneity that may be present in solid tumors, chronic wounds, etc. In this report, we describe the development of a substantially smaller version of OxyChip (0.07 mm3 or 70 cubic micron), called mChip, that can be placed in the tissue of interest using a 23G syringe-needle with minimal invasiveness. Using in vitro and in vivo models, we have shown that the microchip provides adequate EPR sensitivity, stability, and biocompatibility and thus enables robust, repeated, and simultaneous measurement from multiple implants providing mean and median pO2 values in the implanted region. The mChips will be particularly useful for those applications that require repeated measurements of mean/median pO2 in superficial tissues and malignancies.

Diarylidenylpiperidones, H-4073 and HO-3867, Induce G2/M Cell-Cycle Arrest, Apoptosis and Inhibit STAT3 Phosphorylation in Human Pancreatic Cancer Cells.

Pancreatic cancer has a 5-year survival rate below 10% and the treatment options are limited. Signal transducer and activator of transcription (STAT3) is a constitutively expressed protein in human pancreatic cancers and is associated with their poor prognosis. Targeting of STAT3 signaling using novel therapeutic agents is a potential strategy for pancreatic cancer treatment. Diarylidenylpiperidone (DAP) compounds, such as H-4073 and HO-3867, have been shown to be STAT3 inhibitors in several human ovarian cancers. Particularly, HO-3867 is an N-hydroxypyrroline derivative of DAP that has targeted cytotoxicity toward cancer cells without affecting healthy cells. In the present study, we evaluated the anticancer efficacy of H-4073 and HO-3867 in a human pancreatic cell line (AsPC-1). We found that both the compounds exhibited potential cytotoxicity to AsPC-1 cells by inducing G2/M cell-cycle arrest, apoptosis, and cell death, by mitochondrial damage and inhibition of STAT3 phosphorylation. In summary, H-4073 and HO-3867 are cytotoxic to AsPC-1 cells and seem to act through similar mechanisms, including STAT3 inhibition, cell-cycle arrest, and apoptosis.

Hyperoxygenation as a Therapeutic Supplement for Treatment of Triple Negative Breast Cancer.

Triple-negative breast cancer (TNBC) refers to a group of biologically aggressive breast cancers that do not express estrogen, progesterone or epidermal growth factor receptor 2 hormone receptors. Each subset of TNBC has a unique molecular profile and may require specific treatments. A combination of surgery and chemotherapy followed by radiation therapy is the standard treatment mode for TNBC patients. Tumor oxygen status (hypoxia) is a key factor that may compromise the effectiveness of radiation treatment, as it is known that hypoxia can confer radiation resistance. In this study, we characterized MDA-MB-231 orthotropic xenograft tumors with respect to tumor oxygen level and their response to supplemental oxygen therapy in combination with paclitaxel and radiation therapy. We observed that the TNBC tumors became severely hypoxic (pO2 < 4 mmHg) within 1 week of tumor growth and responded poorly to administration of respiratory hyperoxygenation (100% O2) to mitigate hypoxia. However, periodic administration of supplemental oxygen (100% O2; 60 min/day for 21 days) showed a significant inhibitory effect on tumor volume when compared to control (1,023 ± 32 mm3 vs. 1,378 ± 114 mm3; p < 0.05). Combination of supplemental oxygen with paclitaxel and radiation therapy led to a significant reduction in tumor growth when compared to radiation alone (239 ± 40 mm3 vs. 390 ± 32 mm3; p < 0.05). The therapeutic enhancement by supplemental oxygen is possibly attributed to increase in tumor oxygenation with paclitaxel at the time of radiation treatment. These findings may have important implications in the understanding of the role of oxygen and supplemental oxygen therapy for the treatment of TNBC patients.

Ataxia-Telangiectasia Mutated (ATM) Kinase Regulates eNOS Expression and Modulates Radiosensitivity in Endothelial Cells Exposed to Ionizing Radiation.

Endothelial nitric oxide synthase (eNOS), a constitutive enzyme expressed in vascular endothelial cells, is the main source of nitric oxide (NO), which plays key roles in diverse biological functions, including regulation of vascular tone. Exposure to radiation has been known to generate nitric oxide from eNOS; however, the precise mechanism of its generation and function is not known. The goal of this study was to determine the involvement of radiation-induced DNA damage response (DDR) on eNOS transcription and its effect on cell survival after irradiation. Irradiated bovine aortic endothelial cells showed increased eNOS transcription and NO generation through upregulation of ataxia-telangiectasia mutated (ATM) kinase. Radiation exposure induced NO inhibited cell death, as well as induced cellular senescence postirradiation. This study established that radiation-induced DDR uses ATM kinase to upregulate eNOS transcription and NO generation, leading to cellular senescence, which may play a critical role in radiation-mediated cardiovascular injury.