Is cardiac wasting accompanied by skeletal muscle loss in breast cancer patients receiving anticancer treatment?

Recent nanotechnological interventions targeting PI3K/Akt/mTOR pathway: A focus on breast cancer

Breast cancer is the major cause of deaths in women worldwide. Detection and treatment of breast cancer at earlier stages of the disease has shown encouraging results. Modern genomic technologies facilitated several therapeutic options however the diagnosis of the disease at an advanced stage claim more deaths. Therefore more research directed towards genomics and proteomics into this area may lead to novel biomarkers thereby enhancing the survival rates in breast cancer patients. Phosphoinositide-3-kinase/Akt/mammalian target of rapamycin (PI3K/Akt/mTOR) signaling pathway was shown to be hyperactivated in most of the breast carcinomas resulting in excessive growth, proliferation, and tumor development. Development of nanotechnology has provided many interesting avenues to target the PI3K/Akt/mTOR pathway both at the pre-clinical and clinical stages. Therefore, the current review summarizes the underlying mechanism and the importance of targeting PI3K/Akt/mTOR pathway, novel biomarkers and use of nanotechnological interventions in breast cancer.

Metabolic disorders in heart failure and cancer

In an aging population, the number of patients affected by heart failure and cancer is constantly increasing and together these two conditions account for more than 50% of all deaths worldwide. Both diseases share similar risk factors including smoking, obesity, and hypertension. Presenting symptoms may also be similar, with patients frequently complaining of dyspnea, fatigue, and anorexia. Many affected patients, especially those with more advanced heart failure or cancer, suffer also from metabolic disorders. These can lead eventually to muscle wasting, sarcopenia, and cachexia. These complications are associated with increased morbidity, a poorer quality of life, a worse prognosis and indeed they represent an independent risk factor for the advancement of the underlying disease itself. Very few therapeutic options have been established to treat these co-morbidities. For sarcopenia the only validated treatment is resistance training. Moreover, there is currently no guideline recommended therapy for the treatment of cachexia. New treatment strategies are urgently needed to prevent and treat muscle and wasting disorders in patients with chronic diseases such as cancer and chronic heart failure.

The double-edged sword of endoplasmic reticulum stress in uremic sarcopenia through myogenesis perturbation

BACKGROUND

Sarcopenia is the age-related degeneration characterized with the decline of skeletal muscle mass, strength, and function. The imbalance of protein synthesis and degradation which jeopardizes immune, hormone regulation, and muscle-motor neuron connection is the main cause of sarcopenia. There is limited knowledge regarding molecular mechanism of sarcopenia. As the endoplasmic reticulum is the control centre of the protein syntheses and degradation, we hypothesized that endoplasmic reticulum stress and unfolded protein response (UPR) play an important in the development of sarcopenia. Understanding the sarcopenia molecular mechanisms may benefit the therapeutic diagnosis and treatment in the future.

METHODS

Mouse myoblast C2C12 cells are exposed to designated time and concentration of indoxyl sulfate (IS), a uremic toxin of chronic kidney disease. The proliferation, differentiation, and the expression of atrogin 1 are examined. The protein and mRNA expression of IS treated-C2C12 cells are inspected to distinguish the role of ER stress and oxidative stress underlying the sarcopenia.

RESULTS

Indoxyl sulfate inhibits myoblast differentiation. We demonstrate that as the number of multi-nuclei myotube decreased, the differentiation markers including myoD, myoG, and myosin heavy chain are also suppressed. Indoxyl sulfate inhibits myoblast proliferation and induces the myotubular atrophy marker atrogin-1 protein expression. Indoxyl sulfate stimulates eIF2α phosphorylation and XBP1 mRNA splicing in UPR. Interestingly, the oxidative stress is related to eIF2α phosphorylation but not XBP1 mRNA splicing. The eIF2α phosphorylation triggered by IS reduces myoD, myoG, and myosin heavy chain protein expression, which represents the anti-myogenic modulation on the early differentiation event. The XBP1 mRNA splicing induced by IS, however, is considered the adaptive response to restore the myogenic differentiation.

CONCLUSIONS

Our studies indicated that the ER stress and UPR modulation are critical in the chronic kidney disease uremic toxin-accumulated sarcopenia model. We believe that UPR-related signals showed great potential in clinical application.