The bone mineral density (BMD) of the proximal femur, spine and radius shaft was determined in 75 women with atraumatic fractures of the proximal femur (FXf) (average age: 70.1 +/- 9.6 years) and 51 controls of similar age. Fractures were classified as either cervical (n = 36) or trochanteric (n = 39) on the basis of radiographic and surgical finding. The BMD of spine and proximal femur was determined by dual-photon absorptiometry (Lunar DP3) and the BMD of the radius shaft by single photon absorptiometry. The BMD of patients with FXf was significantly decreased over all skeletal sites compared to controls of similar age. No significant correlation was found between age and the BMD of the femoral neck in patients with FXf. Patients with trochanteric FXf were older and thinner (average: age, 72.9 +/- 9.4 years; weight, 53.1 +/- 7.8 kg) compared with patients with cervical fractures (age, 67.2 +/- 8.9 years; weight, 59.3 +/- 8.3 kg). Likewise the BMD of trochanteric FXf was lower at all measured sites: femoral neck, 0.548 +/- 0.066 g/cm2 vs 0.624 +/- 0.055 g/cm2 (P less than 0.001); L2-L4, 0.799 +/- 0.115 g/cm2 vs 0.925 +/- 0.106 g/cm2 (P less than 0.001); radius shaft, 0.454 +/- 0.057 g/cm2 vs 0.502 +/- 0.083 g/cm2 (P less than 0.05). Of the patients with trochanteric fractures 66% had concomitant vertebral fractures, while this occurred in only 28% of the patients with cervical fractures (P (Fisher) = 0.0007). In summary, females with trochanteric FXf are older, thinner, have less bone mass in all measured sites and suffer with a significantly greater frequency of vertebral fractures.(ABSTRACT TRUNCATED AT 250 WORDS)

Pancreatic cancer is one of the most lethal types of tumors with no effective therapy available; is currently the third leading cause of cancer in developed countries; and is predicted to become the second deadliest cancer in the United States by 2030. Due to the marginal benefits of current standard chemotherapy, the identification of new therapeutic targets is greatly required. Considering that cAMP pathway is commonly activated in pancreatic ductal adenocarcinoma (PDAC) and its premalignant lesions, we aim to investigate the multidrug resistance-associated protein 4 (MRP4)-dependent cAMP extrusion process as a cause of increased cell proliferation in human PDAC cell lines. Our results from in silico analysis indicate that MRP4 expression may influence PDAC patient outcome; thus, high MRP4 levels could be indicators of poor survival. In addition, we performed in vitro experiments and identified an association between higher MRP4 expression levels and more undifferentiated and malignant models of PDAC and cAMP extrusion capacity. We studied the antiproliferative effect and the overall cAMP response of three MRP4 inhibitors, probenecid, MK571, and ceefourin-1 in PDAC in vitro models. Moreover, MRP4-specific silencing in PANC-1 cells reduced cell proliferation (P , 0.05), whereas MRP4 overexpression in BxPC-3 cells significantly incremented their growth rate in culture (P , 0.05). MRP4 pharmacological inhibition or silencing abrogated cell proliferation through the activation of the cAMP/Epac/Rap1 signaling pathway. Also, extracellular cAMP reverted the antiproliferative effect of MRP4 blockade. Our data highlight the MRP4-dependent cAMP extrusion process as a key participant in cell proliferation, indicating that MRP4 could be an exploitable therapeutic target for PDAC. SIGNIFICANCE STATEMENTABCC4/MRP4 is the main transporter responsible for cAMP efflux. In this work, we show that MRP4 expression may influence PDAC patient outcome and identify an association between higher MRP4 expression levels and more undifferentiated and malignant in vitro models of PDAC. Findings prove the involvement of MRP4 in PDAC cell proliferation through a novel extracellular cAMP mitogenic pathway and further support MRP4 inhibition as a promising therapeutic strategy for PDAC treatment.