Osteoporosis pharmacogenomics: recent insights and future perspectives

Pharmacogenetics of Response to Bisphosphonate Treatment in Postmenopausal Osteoporosis: A Prospective Study

BACKGROUND

This study aims to investigate the effect of genetic polymorphisms of vitamin D receptor (VDR), estrogen receptor 1 (ER1), and Col1a1 on the response to bisphosphonate (BP) therapy in women with postmenopausal osteoporosis (OP).

METHODS

Twenty-one women with postmenopausal OP who received alendronate, ibandronate, or zoledronic acid for one year were enrolled in this study. Bone mineral density (BMD) at the lumbar spine and femoral neck were assessed by dual energy X-ray absorptiometry at baseline and after 12 months. Serum osteocalcin levels were measured at baseline and after 12 months. Polymorphic sites of the genes encoding ER1, VDR and Col1a1 proteins were amplified by polymerase chain reaction and examined using restriction fragment length polymorphism. Response to BP treatment and change in osteocalcin levels were compared among women with different gene polymorphisms.

RESULTS

Ratio of responders to treatment regarding improvements in the BMD of lumbar spine and femoral neck was adequate in 76% and 62%, respectively. There was no significant difference in treatment response regarding BMD in either region or change in serum osteocalcin levels among different gene polymorphisms.

CONCLUSIONS

These findings did not support the potential role of VDR BsmI, Col1a1 Sp1, ER1 PvuII, or XbaI polymorphisms in predicting the response to BP therapy in women with postmenopausal OP. Further investigation with larger prospective studies is required.

Raloxifene Suppresses Tumor Growth and Metastasis in an Orthotopic Model of Castration-Resistant Prostate Cancer

Androgen receptor (AR)-castrate-resistant prostate cancer (CRPC) is an aggressive form of prostate cancer that does not have clinically approved targeted treatment options. To this end, the cytotoxic potential of raloxifene and the synthetic curcumin derivative 2,6-bis (pyridin-4-ylmethylene)-cyclohexanone (RL91) was examined in AR-(PC3 and DU145) cells and AR+ (LnCaP) CRPC cells. The results showed that both raloxifene and RL91 elicited significant cytotoxicity across three cell lines with the lowest EC₅₀ values in PC3 cells. Additionally, the two drugs were synergistically cytotoxic toward the PC3, DU-145 and LNCaP cell lines. To determine the effect of the drug combination in vivo, an orthotopic model of CRPC was used. Male mice were injected with PC3 prostate cancer cells and then treated with vehicle (5 mL/kg), raloxifene (8.5 mg/kg, po), RL91 (8.5 mg/kg, po) or a combination of raloxifene and RL91 for six weeks. Sham animals were subjected to the surgical procedure but were not implanted with PC3 cells. The results showed that raloxifene decreased tumor size and weight as well as metastasis to renal lymph nodes. However, combination treatment reversed the efficacy of raloxifene as tumor volume and metastasis returned to control levels. The results suggest that raloxifene has tumor suppressive and anti-metastatic effects and has potential for further clinical use in AR-CRPC.

Pharmacogenetics of osteoporosis

The challenge of personalized medicine is to move away from the traditional 'one-size-fits-all' pharmacology to genotype-based individualized therapies. As an individual's response to drugs is under the control of genes, personal genetic profiles could help clinicians to predict individual drug response and prescribe the right drug and dose, thereby optimising efficacy and avoiding risk of adverse effects. Currently, the concrete application of pharmacogenetics into clinical practice is limited to a few drugs, and the genetic prediction of drug response is far from clear for many of thve principal complex disorders. This is even more evident in the field of osteoporosis and metabolic bone disorders, for which few pharmacogenetic studies have been conducted, and no conclusive results are available. In this chapter, we review recent research on pharmacogenetics of osteoporosis, evaluate criticisms, and offer possible suggestions for improvements in this field and for possible future applications into clinical practice.