Mechanisms of doxorubicin-induced drug resistance and drug resistant tumour growth in a murine breast tumour model

BACKGROUND

Doxorubicin is currently the most effective chemotherapeutic drug used to treat breast cancer. It has, however, been shown that doxorubicin can induce drug resistance resulting in poor patient prognosis and survival. Studies reported that the interaction between signalling pathways can promote drug resistance through the induction of proliferation, cell cycle progression and prevention of apoptosis. The aim of this study was therefore to determine the effects of doxorubicin on apoptosis signalling, autophagy, the mitogen-activated protein kinase (MAPK)- and phosphoinositide 3-kinase (PI3K)/Akt signalling pathway, cell cycle control, and regulators of the epithelial-mesenchymal transition (EMT) process in murine breast cancer tumours.

METHODS

A tumour-bearing mouse model was established by injecting murine E0771 breast cancer cells, suspended in Hank's Balances Salt Solution and Corning® Matrigel® Basement Membrane Matrix, into female C57BL/6 mice. Fourty-seven mice were randomly divided into three groups, namely tumour control (received Hank's Balances Salt Solution), low dose doxorubicin (received total of 6 mg/ml doxorubicin) and high dose doxorubicin (received total of 15 mg/ml doxorubicin) groups. A higher tumour growth rate was, however, observed in doxorubicin-treated mice compared to the untreated controls. We therefore compared the expression levels of markers involved in cell death and survival signalling pathways, by means of western blotting and fluorescence-based immunohistochemistry.

RESULTS

Doxorubicin failed to induce cell death, by means of apoptosis or autophagy, and cell cycle arrest, indicating the occurrence of drug resistance and uncontrolled proliferation. Activation of the MAPK/ extracellular-signal-regulated kinase (ERK) pathway contributed to the resistance observed in treated mice, while no significant changes were found with the PI3K/Akt pathway and other MAPK pathways. Significant changes were also observed in cell cycle p21 and DNA replication minichromosome maintenance 2 proteins. No significant changes in EMT markers were observed after doxorubicin treatment.

CONCLUSIONS

Our results suggest that doxorubicin-induced drug resistance and tumour growth can occur through the adaptive role of the MAPK/ERK pathway in an effort to protect tumour cells. Previous studies have shown that the efficacy of doxorubicin can be improved by inhibition of the ERK signalling pathway and thereby treatment failure can be overcome.

Assessing knowledge, attitudes, and practices of healthcare workers regarding medical waste management at a tertiary hospital in Botswana: A cross-sectional quantitative study

Background

Medical waste management (MWM) is of concern to the medical and general community. Adequate knowledge regarding management of healthcare waste is an important precursor to the synthesis of appropriate attitudes and practices of proper handling and disposal of medical waste by healthcare workers (HCWs).

Aims and Objectives

This study was designed to investigate knowledge, attitudes, and practices of doctors, nurses, laboratory technicians, and housekeeping staff, regarding MWM at a tertiary hospital in Gaborone, Botswana.

Materials and Methods

This was a cross-sectional quantitative study using a self-administered questionnaire involving 703 participants. Data were analyzed using SAS software. Descriptive statistics were used to summarize the data. Responses for attitude of respondents were analyzed using nonparametric tests.

Results

The completion rate for this study was 90% with (632/703) questionnaires analyzed. Majority of respondents were nurses 60% (422/703), followed by housekeeping staff 24.3% (171/703), doctors 10.95% (77/703), and laboratory technicians 4.7% (33/703). The study showed that 66.9% (423/632) of respondents had some training in MWM, and 90.5% (572/632) claimed to have knowledge regarding the consequences of poor MWM, particularly health risks. There was a significant agreement among the respondents that segregation of medical waste should be done at the point of generation (mean score = 4.43 out of 5). Majority of respondents reported that the healthcare facility had a color-coding system (mean score = 4.59) and identified "lack of knowledge of the dangers of improper waste management by HCWs" as the major obstacle to MWM.

Conclusion

This study showed that MWM practice at this facility was above average, although improvements were required in accessing waste disposal points and availability of personal protective equipment. Ongoing training should be provided to HCWs on MWM, with more attention to knowledge of regulatory requirements, and involvement of HCWs in development of MWM policies to enhance compliance.

Proteomic analysis of mitochondrial proteins in a mouse model of type 2 diabetes

OBJECTIVE

Impaired mitochondrial function may contribute to the onset of contractile dysfunction with insulin resistance/type 2 diabetes. Our aim was therefore to determine alterations in the mitochondrial proteome of a mouse model of obesity/type 2 diabetes.

METHODS

Mitochondrial proteins were isolated from hearts collected from 18- to 20-week-old female db/db mice and compared to matched controls. We performed two-dimensional polyacrylamide gel electrophoresis to determine differentially expressed proteins. Peptides of interest were further analysed by mass spectrometry and Mascot software was employed to identify protein matches.

RESULTS

Our data showed that ATP synthase D chain, ubiquinol cytochrome-C reductase core protein 1 and electron transfer flavoprotein subunit alpha peptide levels were altered with obesity. Moreover, we found coordinate downregulation of contractile proteins in the obese heart, i.e. α-smooth muscle actin, α-cardiac actin, myosin heavy-chain α and myosin-binding protein C.

CONCLUSION

We propose that decreased contractile protein levels may contribute to contractile dysfunction of hearts from diabetic mice.

Comparison between ischaemic and anisomycin-induced preconditioning: role of p38 MAPK

To further evaluate the significance of p38 MAPK as trigger or mediator in ischaemic preconditioning, anisomycin and SB 203580 were used to manipulate its activation status. Special attention was given to the concentration of the drugs and protocols used. The isolated perfused rat heart, subjected to either 25 min global ischaemia or 35 min regional ischaemia, was used as experimental model. This was preceded by anisomycin (2 or 5 muM: 3 x 5 min; 5 muM: 5 min or 10 min; 5 muM: 10 min + 10 min washout or 20 muM: 20 min) or SB 203580 (2 muM: 3 x 5 min; before and during 3 x 5 min or 1 x 5 min ischaemic preconditioning; 10 min). Endpoints were functional recovery during reperfusion and infarct size.Anisomycin, regardless of the protocol, reduced infarct size, but did not improve functional recovery. In a number of experiments activation of JNK by anisomycin was blocked by SP 600125 (10 muM). SP 600125 had no effect on the anisomycin-induced reduction in infarct size. SB 203580 when administered for 10 min before sustained ischaemia, improved functional recovery and reduced infarct size. SB 203580 could not abolish the beneficial effects of a multi-cycle preconditioning protocol, but it significantly reduced the outcome of 1 x 5 min preconditioning. In all hearts improved functional recovery and reduction in infarct size were associated with attenuation of p38 MAPK activation during sustained ischaemia-reperfusion. The results indicate that activation of p38 MAPK acts as a trigger of preconditioning, while attenuation of its activation is a prerequisite for improved recovery and a reduction in infarct size.

[Profile of the community health nurse]

This article highlights the profile of the community health nurse in the South African context. Our changing society and also the move in emphasis to primary health care services places great emphasis on the important role of the community health nurse in the health services of the future. A brief historical overview gives the development of the training for community health nurses in this country from the traditional health visitor, to the present day comprehensive basic training where community health is seen as part of the basic training for nurses. The answer to questions such as who and what is the community health nurse in South Africa is discussed and some essential characteristics of this nurse are described. Recent South African Nursing Council statistics reveal that only 7 percent of all registered nurses have the additional qualification in community health. Other statistics provide a view on numbers of registered nurses with the additional qualification in the different race groups.