Glucocorticoids attenuate the sensitivity of glucocorticoid-resistant lymphoid cells to doxorubicin via reduction in OCTN2

Advantages and drawbacks of dexamethasone in glioblastoma multiforme

The most widespread, malignant, and deadliest type of glial tumor is glioblastoma multiforme (GBM). Despite radiation, chemotherapy, and radical surgery, the median survival of afflicted individuals is about 12 months. Unfortunately, existing therapeutic interventions are abysmal. Dexamethasone (Dex), a synthetic glucocorticoid, has been used for many years to treat brain edema and inflammation caused by GBM. Several investigations have recently shown that Dex also exerts antitumoral effects against GBM. On the other hand, more recent disputed findings have questioned the long-held dogma of Dex treatment for GBM. Unfortunately, steroids are associated with various undesirable side effects, including severe immunosuppression and metabolic changes like hyperglycemia, which may impair the survival of GBM patients. Current ideas and concerns about Dex's effects on GBM cerebral edema, cell proliferation, migration, and its clinical outcomes were investigated in this study.

Effect of prednisolone pre-treatment on cat lymphoma cell sensitivity towards chemotherapeutic drugs

Corticosteroid administration prior to the application of chemotherapy in small animal lymphoma patients is a concern, as it is discussed to negatively influence the therapeutic outcome due to corticosteroid-induced drug resistance. Using feline lymphoma cell lines FT-1 and MS4 we have shown, that prednisolone pre-treatment alters the susceptibility of these cells towards doxorubicin or vincristine treatment in vitro. The observed effect was negative as for the killing potential and it was cell line and drug (doxorubicin or vincristine) dependent. Furthermore, increase in mRNA expression of selected proteins with multidrug resistance potential (MDR1, BCRP, LRP, MT) was observed after prednisolone pre-treatment. Administration of chemical inhibitors of these proteins did not lead to reversal in sensitivity of tested cell lines to doxorubicin or vincristine.

Drug uptake-based chemoresistance in breast cancer treatment

Breast cancer is the most prevalent type of tumor and the second leading cause of death due to cancer among women. Although screening methods, diagnosis and therapeutic options have improved in the last decade, chemoresistance remains an important challenge. There is evidence relating breast cancer resistance with signaling pathways involving hormone and growth receptors, survival, apoptosis and the activation of efflux pumps. However, the resistance mechanisms linked to drug uptake are poorly understood, despite it often being observed that the drug content is lower in resistant cancer cells and that the entry of the drug into these cells is a limiting process for the subsequent therapeutic effect.In this review, we provide an overview of drug uptake-based resistance mechanisms developed by cancer cells in the four main types of chemotherapy used in breast cancer: anthracyclines, taxanes, oxazaphosphorines and platinum-based drugs. The contribution of tumor microenvironment to reduced drug-uptake and multidrug resistance is also analyzed. As a developing field, nanomedicine-based approaches provide promising opportunities to improve drug specific targeting, cell interaction and uptake into cancer cells. The endocytic-mediated pathways attributed to the different types of nanoformulations as well as the contribution of nanotherapeutics to overcoming chemoresistance affecting drug uptake in breast cancer will be described. New approaches focusing on drug uptake mechanisms could improve breast cancer chemotherapy, obtaining better dose-response outcomes and reducing toxic side effects.