Different Efflux Transporter Affinity and Metabolism of 99mTc-2-Methoxyisobutylisonitrile and 99mTc-Tetrofosmin for Multidrug Resistance Monitoring in Cancer

Sorafenib Chemosensitization by Caryophyllane Sesquiterpenes in Liver, Biliary, and Pancreatic Cancer Cells: The Role of STAT3/ABC Transporter Axis

A combination of anticancer drugs and chemosensitizing agents has been approached as a promising strategy to potentiate chemotherapy and reduce toxicity in aggressive and chemoresistant cancers, like hepatocellular carcinoma (HCC), cholangiocarcinoma (CCA), and pancreatic ductal adenocarcinoma (PDAC). In the present study, the ability of caryophyllane sesquiterpenes to potentiate sorafenib efficacy was studied in HCC, CCA, and PDAC cell models, focusing on the modulation of STAT3 signaling and ABC transporters; tolerability studies in normal cells were also performed. Results showed that the combination of sorafenib and caryophyllane sesquiterpenes synergized the anticancer drug, especially in pancreatic Bx-PC3 adenocarcinoma cells; a similar trend, although with lower efficacy, was found for the standard ABC transporter inhibitors. Synergistic effects were associated with a modulation of MDR1 (or Pgp) and MRP transporters, both at gene and protein level; moreover, activation of STAT3 cascade and cell migration appeared significantly affected, suggesting that the STAT3/ABC-transporters axis finely regulated efficacy and chemoresistance to sorafenib, thus appearing as a suitable target to overcome drawbacks of sorafenib-based chemotherapy in hepato-biliary-pancreatic cancers. Present findings strengthen the interest in caryophyllane sesquiterpenes as chemosensitizing and chemopreventive agents and contribute to clarifying drug resistance mechanisms in HCC, CCA, and PDAC cancers and to developing possible novel therapeutic strategies.

Inhibition of the Hepatic Uptake of 99mTc-Tetrofosmin Using an Organic Cation Transporter Blocker

The accumulation of high levels of ^99mTc-tetrofosmin (^99mTc-TF) in the hepatobiliary system can lead to imaging artifacts and interference with diagnosis. The present study investigated the transport mechanisms of ^99mTc-TF and attempted to apply competitive inhibition using a specific inhibitor to reduce ^99mTc-TF hepatic accumulation. In this in vitro study, ^99mTc-TF was incubated in HEK293 cells expressing human organic anion transporting polypeptide 1B1 (OATP1B1), OATP1B3, OATP2B1, organic anion transporter 2 (OAT2), organic cation transporter 1 (OCT1), OCT2, and Na⁺-taurocholate cotransporting polypeptide with or without each specific inhibitor to evaluate the contribution of each transporter to ^99mTc-TF transportation. In vivo studies, dynamic planar imaging, and single photon emission computed tomography (SPECT) experiments with rats were performed to observe alterations to ^99mTc-TF pharmacokinetics using cimetidine (CMT) as an OCT1 inhibitor. Time-activity curves in the liver and heart were acquired from dynamic data, and the ^99mTc-TF uptake ratio was calculated from SPECT. From the in vitro study, ^99mTc-TF was found to be transported by OCT1 and OCT2. When CMT-preloaded rats and control rats were compared, the hepatic accumulation of the ^99mTc-TF was reduced, and the time to peak heart count shifted to an earlier stage. The hepatic accumulation of ^99mTc-TF was markedly suppressed, and the heart-to-liver ratio increased 1.6-fold. The pharmacokinetics of ^99mTc-TF were greatly changed by OCT1 inhibitor. Even in humans, the administration of OCT1 inhibitor before cardiac SPECT examination may reduce ^99mTc-TF hepatic accumulation and contribute to the suppression of artifacts and the improvement of SPECT image quality.

The Potential Cytotoxic Activity Enhancement of α-Mangostin in Chitosan-Kappa Carrageenan-Loaded Nanoparticle against MCF-7 Cell Line

α-mangostin (αM), a xanthone derivative compound isolated from the extract of mangosteen pericarp (Garcinia mangostana L), has potential anticancer properties for breast cancer. However, it has poor solubility in water and low selectivity towards cancer cells. The polymeric nanoparticle formulation approach can be used to overcome these problems. In this study, a chitosan biopolymer-based αM polymeric nanoparticle formulation was encapsulated using kappa carrageenan (αM-Ch/Cr) as a novel carrier for breast cancer therapy and evaluated for their physicochemical properties, drug release profile, and in vitro cytotoxicity against breast cancer cells (MCF-7). Polymeric nanoparticles formulated with varying concentrations of kappa carrageenan were successfully prepared by ionic gelation and spray pyrolysis techniques. αM-Ch/Cr nanoparticles formed perfectly round particles with a size of 200–400 nm and entrapment efficiency ≥ 98%. In vitro release studies confirmed that αM-Ch/Cr nanoparticles had a sustained release system profile. Interestingly, the formulation of polymeric nanoparticles significantly (p < 0.05) increased the cytotoxicity of αM against MCF-7 cell with IC50 value of 4.7 μg/mL compared to the non-nanoparticle with IC50 of 8.2 μg/mL. These results indicate that αM-Ch/Cr nanoparticles have the potential to improve the physicochemical properties and cytotoxicity effects of αM compounds as breast cancer therapy agents.

A multidrug resistance-associated protein inhibitor is a potential enhancer of the benzyl isothiocyanate-induced apoptosis induction in human colorectal cancer cells

The increasing drug efflux through the ATP-binding cassette (ABC) transporters is the most plausible mechanism that mediates resistance to the anticancer phytochemicals, such as benzyl isothiocyanate (BITC), as well as chemotherapy drugs. To identify a potential component to overcome this resistance by combinatory utilization, we focused on multidrug resistance-associated proteins (MRPs) pumping various drug metabolites with glutathione as well as the organic anions. The pharmacological treatment of an MRP inhibitor, MK571, significantly potentiated the BITC-induced antiproliferation, coincided with the enhanced accumulation of BITC and glutathione in human colorectal cancer HCT-116 cells. MK571 also enhanced the apoptosis induction as well as activation of the mitogen-activated protein kinases and caspase-3, whereas it did not affect their basal levels. These results suggested that, since MRPs might play a pivotal role in the BITC efflux, MK571 potentiates the BITC-induced antiproliferation in human colorectal cancer cells through inhibition of the glutathione-dependent BITC efflux.

Assessment of drug transporters involved in the urinary secretion of [99mTc]dimercaptosuccinic acid

INTRODUCTION

We clarified the renal uptake and urinary secretion mechanism of [^99mTc]dimercaptosuccinic acid ([^99mTc]DMSA) via drug transporters in renal proximal tubules.

METHODS

[^99mTc]DMSA was added to human embryonic kidney 293 cells expressing human multidrug and toxin extrusion (MATE)1 and MATE2-K, carnitine/organic cation transporter (OCTN)1 and OCTN2, and organic cation transporter (OCT)2; to Flp293 cells expressing human organic anion transporter (OAT)1 and OAT3; and to vesicles expressing P-glycoprotein (P-gp), multidrug resistance associated protein (MRP)2, MRP4, or breast cancer resistance protein with and without probenecid (OAT inhibitor for both OATs and MRPs). Time activity curves of [^99mTc]DMSA with and without probenecid were established using LLC-PK₁ cells. Biodistribution and single photon emission computed tomography (SPECT) imaging in mice were conducted using [^99mTc]DMSA with and without probenecid.

RESULTS

[^99mTc]DMSA uptake was significantly higher in Flp293/OAT3 than in mock cells. Uptake via OAT3 was inhibited by probenecid. [^99mTc]DMSA uptake into vesicles that highly expressed MRP2 was significantly higher in adenosine triphosphate (ATP) than in adenosine monophosphate (AMP), and probenecid decreased uptake to similar levels as that in AMP. In the time activity curves for [^99mTc]DMSA in LLC-PK₁ cells, probenecid loading inhibited accumulation from the basolateral side into LLC-PK₁ cells, whereas accumulation from the apical side into cells gradually increased. Transport of [^99mTc]DMSA from both sides was low. Biodistribution and SPECT imaging studies showed that [^99mTc]DMSA with probenecid loading resulted in significantly higher accumulation in blood, heart, liver, and bladder after [^99mTc]DMSA injection compared with control mice. Probenecid induced significantly lower accumulation in the kidney after [^99mTc]DMSA injection.

CONCLUSIONS

[^99mTc]DMSA accumulates in renal proximal tubular epithelial cells from blood via OAT3 on the basolateral side, and then a small volume of [^99mTc]DMSA will be excreted in urine via MRP2. ADVANCES IN KNOWLEDGE: [^99mTc]DMSA accumulates via OAT3 in renal proximal tubular epithelial cells and is slightly excreted from the cells via MRP2. IMPLICATIONS FOR PATIENT CARE: [^99mTc]DMSA may be useful for measuring renal transport function with OAT3 in patients.

[131I]MIBG exports via MRP transporters and inhibition of the MRP transporters improves accumulation of [131I]MIBG in neuroblastoma

INTRODUCTION

¹³¹I-labeled m-iodobenzylguanidine ([¹³¹I]MIBG) has been used to treat neuroblastoma patients, but [¹³¹I]MIBG may be immediately excreted from the cancer cells by the adenosine triphosphate binding cassette transporters, similar to anticancer drugs. The purpose of this study was to clarify the efflux mechanism of [¹³¹I]MIBG in neuroblastomas and improve accumulation by inhibition of the transporter in neuroblastomas.

METHODS

[¹³¹I]MIBG was incubated in human embryonic kidney (HEK)293 cells expressing human organic anion transporting polypeptide (OATP)1B1, OATP1B3, OATP2B1, organic anion transporter (OAT)1 and OAT2, organic cation transporter (OCT)1 and OCT2, and sodium taurocholate cotransporting polypeptide, and in vesicles expressing P-glycoprotein (MDR1), multidrug resistance associated protein (MRP)1-4, or breast cancer resistance protein with and without MK-571 and probenecid (MRP inhibitors). Time activity curves of [¹³¹I]MIBG with and without MK-571 and probenecid were established using an SK-N-SH neuroblastoma cell line, and transporter expression of multiple drug resistance was measured. Biodistribution and SPECT imaging examinations were conducted using [¹²³I]MIBG with and without probenecid in SK-N-SH-bearing mice.

RESULTS

[¹³¹I]MIBG uptake was significantly higher in OAT1, OAT2, OCT1, and OCT2 than in mock cells. Uptake via OCT1 and OCT2 was little inhibited by MK-571 and probenecid. [¹³¹I]MIBG uptake into vesicles that highly expressed MRP1 or MRP4 was significantly higher in ATP than in AMP, and these inhibitors restored uptake to levels similar to that in AMP. Examining the time activity curves for [¹³¹I]MIBG in SK-N-SH cells, higher expressions of MDR1, MRP1, MRP4, and MK-571, or probenecid loading produced significantly higher uptake than in control at most incubation times. The ratios of tumors to blood or muscle in SK-N-SH-bearing mice were significantly increased by probenecid loading in comparison with normal mice.

CONCLUSIONS

[¹³¹I]MIBG exports via MRP1 and MRP4 in neuroblastoma. The accumulation and tumor-to-blood or muscle ratios of [¹³¹I]MIBG are improved by inhibition of MRPs with probenecid in neuroblastoma. ADVANCES IN KNOWLEDGE: [¹³¹I]MIBG, widely used for treatment of neuroendocrine tumors including neuroblastoma, is excreted via MRP1 and MRP4 in neuroblastoma.

IMPLICATIONS FOR PATIENT CARE

Loading with probenecid, OAT, and MRP inhibitors improves [¹³¹I]MIBG accumulation.

The effects of pharmacological interventions, exercise, and dietary supplements on extra-cardiac radioactivity in myocardial perfusion single-photon emission computed tomography imaging

Myocardial perfusion imaging (MPI) as an imaging modality plays a key role in the monitoring of patients with cardiovascular disease. MPI enables the assessment of cardiovascular disease, the effectiveness of therapy, and viable myocardial tissue. However, MPI suffers from some downfalls and limitations, which can influence its clinical applications. These limitations can arise from the patient's condition, equipment, or the actions of the technologist. In this review, we mainly focused on the different effective parameters on radioactivity uptake of organs including liver, intestines, stomach, and gall bladder and how they affect the quality of the acquired images in nuclear medicine. More importantly, we cover how different suggested medicines, foods and exercise alleviative this problem.

Imaging of hepatic drug transporters with [131I]6-β-iodomethyl-19-norcholesterol

We examined whether [¹³¹I]6-β-iodomethyl-19-norcholesterol (NP-59), a cholesterol analog, can be used to measure function of hepatic drug transporters. Hepatic uptake of NP-59 with and without rifampicin was evaluated using HEK293 cells expressing solute carrier transporters. The stability of NP-59 was evaluated using mouse blood, bile, and liver, and human liver S9. Adenosine triphosphate-binding cassette (ABC) transporters for bile excretion were examined using hepatic ABC transporter vesicles expressing multidrug resistance protein 1, multidrug resistance-associated protein (MRP)1-4, breast cancer resistance protein (BCRP), or bile salt export pump with and without MK-571 and Ko143. Single photon emission computed tomography (SPECT) was performed in normal mice injected with NP-59 in the presence or absence of Ko143. Uptake of NP-59 into HEK293 cells expressing organic anion transporting polypeptide (OATP)1B1 and OATP1B3 was significantly higher than that into mock cells and was inhibited by rifampicin. NP-59 was minimally metabolized in mouse blood, bile, and liver, and human liver S9 after 120 min of incubation. In vesicles, NP-59 was transported by MRP1 and BCRP. Excretion of NP-59 into bile via BCRP was observed in normal mice with and without Ko143 in the biological distribution and SPECT imaging. NP-59 can be used to visualize and measure the hepatic function of OATP1B1, OATP1B3, and BCRP.