DHEA treatment: myth or reality?

Dehydroepiandrosterone (DHEA) and its sulfate ester are major secretory products of the human adrenal. Serum DHEA concentrations decline with advancing age and DHEA supplementation in elderly people has been advertized as anti-aging medication. However, such claims are based on experiments in rodents with a fundamentally different DHEA physiology. In humans, DHEA is a crucial precursor of sex steroid biosynthesis and exerts indirect endocrine and intracrine actions following conversion to androgens and estrogens. In addition, it acts as a neurosteroid via effects on neurotransmitter receptors in the brain. DHEA has considerable effects on mood, well-being and sexuality in patients with adrenal insufficiency, and also in those with mood disorders. However, subjects with a physiological, age-related decline in DHEA secretion show little benefit from DHEA administration. Future research should focus on DHEA treatment for adrenal insufficiency, and DHEA administration in both patients receiving chronic glucocorticoid treatment and women with androgen deficiency.     

Analysing time to event data in dementia prevention trials: The example of the guidage study of EGB761®

Time-to-event analysis is frequently used in medical research to investigate potential diseasemodifying treatments in neurodegenerative diseases. Potential treatment effects are generally evaluated using the logrank test, which has optimal power and sensitivity when the treatment effect (hazard ratio) is constant over time. However, there is generally no prior information as to how the hazard ratio for the event of interest actually evolves. In these cases, the logrank test is not necessarily the most appropriate to use. When the hazard ratio is expected to decrease or increase over time, alternative statistical tests such as the Fleming-Harrington test, provide a better sensitivity. An example of this comes from a large, five-year randomised, placebo-controlled prevention trial (GuidAge) in 2854 community-based subjects making spontaneous memory complaints to their family physicians, which evaluated whether treatment with EGb761® can modify the risk of developing AD. The primary outcome measure was the time to conversion from memory complaint to Alzheimer’s type dementia. Although there was no significant difference in the hazard function of conversion between the two treatment groups according to the preplanned logrank test, a significant treatment-by-time interaction for the incidence of AD was observed in a protocol-specified subgroup analysis, suggesting that the hazard ratio is not constant over time. For this reason, additional post hoc analyses were performed using the Fleming-Harrington test to evaluate whether there was a signal of a late effect of EGb761®. Applying the Fleming-Harrington test, the hazard function for conversion to dementia in the placebo group was significantly different from that in the EGb761® treatment group (p = 0.0054), suggesting a late effect of EGb761®. Since this was a post hoc analysis, no definitive conclusions can be drawn as to the effectiveness of the treatment. This post hoc analysis illustrates the interest of performing another randomised clinical trial of EGb761® explicitly testing the hypothesis of a late treatment effect, as well as of using of better adapted statistical approaches for long term preventive trials when it is expected that prevention cannot have an immediate effect but rather a delayed effect that increases over time.     

Bisphosphonates as anticancer agents in early breast cancer: preclinical and clinical evidence

Bisphosphonates (BPs) are approved as standard therapy in breast cancer for the treatment of bone metastases, since they were demonstrated to reduce the prevalence of skeletal-related events including fractures and hypercalcemia. In the adjuvant setting, BPs can be given to prevent and treat tumor therapy-induced bone loss in premenopausal and postmenopausal women and, owing to their beneficial effect on bone turnover, have also been evaluated for prevention of bone metastases occurrence. In this article we will review the mechanisms through which BPs have been demonstrated to prevent premetastatic niche formation and cell proliferation in bone lesions. Moreover, preclinical evidence of antitumoral effects of BPs will be presented and results from the most important clinical trials will be described critically. BPs may clearly play a clinically important role in early breast cancer in a postmenopausal adjuvant setting.     

PI3K inhibition synergizes with glucocorticoids but antagonizes with methotrexate in T-cell acute lymphoblastic leukemia

The PI3K pathway is frequently hyperactivated in primary T-cell acute lymphoblastic leukemia (T-ALL) cells. Activation of the PI3K pathway has been suggested as one mechanism of glucocorticoid resistance in T-ALL, and patients harboring mutations in the PI3K negative regulator PTEN may be at increased risk of induction failure and relapse. By gene expression microarray analysis of T-ALL cells treated with the PI3K inhibitor AS605240, we identified Myc as a prominent downstream target of the PI3K pathway. A significant association was found between the AS605240 gene expression signature and that of glucocorticoid resistance and relapse in T-ALL. AS605240 showed anti-leukemic activity and strong synergism with glucocorticoids both in vitro and in a NOD/SCID xenograft model of T-ALL. In contrast, PI3K inhibition showed antagonism with methotrexate and daunorubicin, drugs that preferentially target dividing cells. This antagonistic interaction, however, could be circumvented by the use of correct drug scheduling schemes. Our data indicate the potential benefits and difficulties for the incorporation of PI3K inhibitors in T-ALL therapy.