On-chip photodynamic therapy - monitoring cell metabolism using electrochemical microsensors.

We introduce a new system which combines metabolic monitoring using electrochemical microsensors with photodynamic therapy on-chip for the first time. Oxygen consumption of T-47D breast cancer cells was measured during therapy with protoporphyrin IX. We determined the efficacy of the therapy and revealed its recovery effects, which underlines the high relevance of continuous monitoring.

Sensor Access to the Cellular Microenvironment Using the Sensing Cell Culture Flask.

The Sensing Cell Culture Flask (SCCF) is a cell culture monitoring system accessing the cellular microenvironment in 2D cell culture using electrochemical microsensors. The system is based on microfabricated sensor chips embedded in standard cell culture flasks. Ideally, the sensor chips could be equipped with any electrochemical sensor.

Low dose-rate irradiation with [H]-labelled valine to selectively target hypoxic cells in a human colorectal cancer xenograft model.

Background: Earlier in vitro studies show that irradiation with an ultra-low dose-rate of 15 mGy/h delivered with [H]-valine leads to loss of clonogenicity in hypoxic T-47D cells. Here, the aim was to determine if [H]-valine could be used to deliver low dose-rate irradiation in a colorectal cancer model.

Methods: Clonogenicity was measured in cultured cancer cell line HT29 irradiated with 15 mGy/h combined with intermittent hypoxia.

Separation of two sub-groups with different DNA content after treatment of T-47D breast cancer cells with low dose-rate irradiation and intermittent hypoxia.

Background Previous studies have shown that combined treatment with internal ultra-low dose-rate irradiation selectively inactivated hypoxic T-47D breast cancer cells after three to five weeks of treatment. However, 2-3% of the hypoxic cells were found to survive and restart proliferation upon re-oxygenation. Purpose To investigate the metastatic potential and characteristics of radiosensitivity of these surviving cells, named T - 47 D.

Low-Dose-Rate Irradiation for 1 Hour Induces Protection Against Lethal Radiation Doses but Does Not Affect Life Span of DBA/2 Mice.

Prior findings showed that serum from DBA/2 mice that had been given whole-body irradiation for 1 hour at a low dose rate (LDR) of 30 cGy/h induced protection against radiation in reporter cells by a mechanism depending on transforming growth factor β3 and inducible nitric oxide synthase activity. In the present study, the effect of the 1 hour of LDR irradiation on the response of the preirradiated mice to a subsequent lethal dose and on the life span is examined. These DBA/2 mice were prime irradiated for 1 hour at 30 cGy/h.

Hypoxia Strongly Affects Mitochondrial Ribosomal Proteins and Translocases, as Shown by Quantitative Proteomics of HeLa Cells.

Hypoxia is an important and common characteristic of many human tumors. It is a challenge clinically due to the correlation with poor prognosis and resistance to radiation and chemotherapy. Understanding the biochemical response to hypoxia would facilitate the development of novel therapeutics for cancer treatment.

Rheological characterization of an injectable alginate gel system.

Background: This work investigates a general method for producing alginate gel matrices using an internal mode of gelation that depends solely on soluble alginate and alginate/gelling ion particles. The method involves the formulation of two-component kits comprised of soluble alginate and insoluble alginate/gelling ion particles. Gelling kinetics, elastic and Young's moduli were investigated for selected parameters with regard to soluble alginate guluronate content, molecular weight, calcium or strontium gelling ions and alginate gelling ion particle sizes in the range between 25 and 125 micrometers.

Microenvironment-dependent respiration of T-47D cells cultured in alginate biostructures.

Objectives: The main objective of this paper was to investigate whether the oxygen consumption rate (OCR) of cells entrapped in alginate hydrogels depends on presence of soluble factors present in foetal bovine serum (FBS).

Materials And Methods: Pericellular oxygen concentrations were measured using a photochemical oxygen sensor inserted into bioconstructs made from different formulations of alginate, containing T-47D cells. Cell count was corrected for viability as determined by cell uptake and exclusion of standard live/dead fluorophores, in sections of freshly prepared biostructures.

Cell inactivation by combined low dose-rate irradiation and intermittent hypoxia.

Purpose: To investigate in detail the earlier observed combined effect of low dose-rate β-irradiation delivered at a dose-rate of 15 mGy/h and continued intermittent hypoxia that leads to extensive cell death after approximately 3-6 weeks.

Material And Methods: Continuous low dose-rate β-irradiation at a dose rate of 15, 1.5 or 0.

Targeting tumour hypoxia to prevent cancer metastasis. From biology, biosensing and technology to drug development: the METOXIA consortium.

The hypoxic areas of solid cancers represent a negative prognostic factor irrespective of which treatment modality is chosen for the patient. Still, after almost 80 years of focus on the problems created by hypoxia in solid tumours, we still largely lack methods to deal efficiently with these treatment-resistant cells. The consequences of this lack may be serious for many patients: Not only is there a negative correlation between the hypoxic fraction in tumours and the outcome of radiotherapy as well as many types of chemotherapy, a correlation has been shown between the hypoxic fraction in tumours and cancer metastasis.

The roles of TGF-β3 and peroxynitrite in removal of hyper-radiosensitivity by priming irradiation.

Purpose: To investigate the mechanisms inducing and maintaining the permanent elimination of low dose hyper-radiosensitivity (HRS) in cells given a dose of 0.3 Gy at low dose-rate (LDR) (0.3 Gy/h).

The role of nitric oxide radicals in removal of hyper-radiosensitivity by priming irradiation.

In this study, a mechanism in which low-dose hyper-radiosensitivity (HRS) is permanently removed, induced by low-dose-rate (LDR) (0.2-0.3 Gy/h for 1 h) but not by high-dose-rate priming (0.

Alterations of monocarboxylate transporter densities during hypoxia in brain and breast tumour cells.

Background: Tumour cells are characterized by aerobic glycolysis, which provides biomass for tumour proliferation and leads to extracellular acidification through efflux of lactate via monocarboxylate transporters (MCTs). Deficient and spasm-prone tumour vasculature causes variable hypoxia, which favours tumour cell survival and metastases. Brain metastases frequently occur in patients with advanced breast cancer.

Low dose hyper-radiosensitivity is eliminated during exposure to cycling hypoxia but returns after reoxygenation.

Purpose: To investigate the effect of cycling hypoxia on low dose hyper-radiosensitivity (HRS).

Materials And Methods: Human breast tumor T-47D cells were grown in a hypoxia workstation operated at 4% O(2) for 3-6 weeks and the pericellular oxygen concentration was recorded every 20 minutes. The presence of HRS in response to subsequent challenge irradiation was measured by clonogenic survival.

Mechanisms of the elimination of low dose hyper-radiosensitivity in T-47D cells by low dose-rate priming.

Purpose: To investigate the mechanisms of elimination of low-dose hyper-radiosensitivity (HRS) in T-47D cells induced by 0.3 Gy low dose-rate (LDR) priming.

Materials And Methods: The mitotic ratio was measured using mitotic marker histone H3 phosphorylation in LDR primed as well as untreated T-47D cells.

Taking advantage of tumor cell adaptations to hypoxia for developing new tumor markers and treatment strategies.

Cancer cells in hypoxic areas of solid tumors are to a large extent protected against the action of radiation as well as many chemotherapeutic drugs. There are, however, two different aspects of the problem caused by tumor hypoxia when cancer therapy is concerned: One is due to the chemical reactions that molecular oxygen enters into therapeutically targeted cells. This results in a direct chemical protection against therapy by the hypoxic microenvironment, which has little to do with cellular biological regulatory processes.

The elimination of low-dose hyper-radiosensitivity by transfer of irradiated-cell conditioned medium depends on dose rate.

Irradiation of T-47D cells with 0.3 Gy delivered by a (60)Co source at a low dose rate of 0.3 Gy/h abolished low-dose hyper-radiosensitivity (HRS) for at least 14 months (with continuous cell culturing), while the same dose administered acutely (40 Gy/h) eliminated HRS for less than 24 h.

Radiobiological responses for two cell lines following continuous low dose-rate (CLDR) and pulsed dose rate (PDR) brachytherapy.

The iso-effective irradiation of continuous low-dose-rate (CLDR) irradiation was compared with that of various schedules of pulsed dose rate (PDR) irradiation for cells of two established human lines, T-47D and NHIK 3025. Complete single-dose response curves were obtained for determination of parameters alpha and beta by fitting of the linear quadratic formula. Sublethal damage repair constants micro and T(1/2) were determined by split-dose recovery experiments.

The role of p27 in controlling the oxygen-dependent checkpoint of mammalian cells in late G1.

We have studied hypoxia-induced cell cycle arrest in human cells where the retinoblastoma tumour suppressor protein (pRb) is either functional (T-47D cells) or abrogated by expression of the HPV18 E7 oncoprotein (NHIK 3025 cells). Cells of both types are arrested in a restriction point in late G1, here denoted as the oxygen-dependent restriction point in late G1. This arrest seems to occur under extreme hypoxia in all types of mammalian cells so far tested.

Pericellular oxygen depletion during ordinary tissue culturing, measured with oxygen microsensors.

Recent research has found important differences in oxygen tension in proximity to certain mammalian cells when grown in culture. Oxygen has a low diffusion rate through cell culture media, thus, as a result of normal respiration, a decrease in oxygen tension develops close to the cells. Therefore, for the purpose of standardization and optimization, it is important to monitor pericellular oxygen tension and cell oxygen consumption.

pH effects on the cellular uptake of four photosensitizing drugs evaluated for use in photodynamic therapy of cancer.

The difference in extracellular pH in malignant as compared to normal healthy tissues has been proposed to contribute to selective uptake of photosensitizers in tumors. Hematoporphyrin IX (HpIX), disulfonated meso-tetraphenylporphine (TPPS(2a)), meso-tetra(3-hydroxyphenyl)porphine (mTHPP) and meso-tetra(3-hydroxyphenyl)chlorin (mTHPC) were chosen to examine the pH dependence of their cellular drug uptake. The study was performed in the pH range 6.

Cell cycle inhibitors and outcome after radiotherapy in bladder cancer patients.

The aim of this study was to correlate the expression of cell cycle inhibitors with outcome of patients with muscle-invasive bladder cancer treated with preoperative radiotherapy (46 Gy/4-5 weeks or 20 Gy/1 week) and cystectomy. Patients with pT3b (n = 42) or pT0 (n = 17) were included in the study. Expression of p16INK4a and p27KIP1 was assessed immunohistochemically in pre-radiotherapy biopsies and cystectomy specimens.

Role of ribonucleotide reductase in regulation of cell cycle progression during and after exposure to moderate hypoxia.

Earlier studies have shown that the retinoblastoma protein (pRb) is involved in cell-cycle regulation under conditions of moderate hypoxia, which is the term we use to denote oxygen concentrations just above the lower level giving full respiration, ie. 1300 ppm O2. We have studied the cell cycle regulatory influence of varying levels of ribonucleotide reductase under moderate hypoxia in human cancer cells with either functional (T47D and T47DHU-res) or non-functional pRb due to expression of HPV18 E7 (HeLa S3).