Synthesis and biological evaluation of isoprenylated coumarins as potential anti-pancreatic cancer agents.

A series of isoprenylated coumarins has been designed, synthesized, and evaluated against human pancreatic adenocarcinoma cell line PANC-1 under nutrient-rich and nutrient-deprived conditions. The compounds described investigate the effect of isoprenyl chain length and positioning on cell growth inhibition. The majority of these compounds displayed cytotoxicity against PANC-1 cells selectively in the absence of essential amino acids, glucose, and serum, and showed no cytotoxicity under nutrient-rich conditions. In this study, compound 6 exhibited the highest cytotoxic activity with an LC50 value of 4µM and induced apoptosis-like morphological changes in PANC-1 cells after a 24-h incubation. The evaluated structure-activity relationships show that substitution at the 6-position and the presence of a farnesyl isoprenyl tail are important structural features for enhanced preferential cytotoxicity. These findings provide important information to designing other structural analogues for potential application as novel pancreatic antitumor agents.

Protection against Staphylococcus aureus Colonization and Infection by B- and T-Cell-Mediated Mechanisms.

Staphylococcus aureus is a major cause of morbidity and mortality worldwide. S. aureus colonizes 20 to 80% of humans at any one time and causes a variety of illnesses. Strains that are resistant to common antibiotics further complicate management. S. aureus vaccine development has been unsuccessful so far, largely due to the incomplete understanding of the mechanisms of protection against this pathogen. Here, we studied the role of different aspects of adaptive immunity induced by an S. aureus vaccine in protection against S. aureus bacteremia, dermonecrosis, skin abscess, and gastrointestinal (GI) colonization. We show that, depending on the challenge model, the contributions of vaccine-induced S. aureus-specific antibody and Th1 and Th17 responses to protection are different: antibodies play a major role in reducing mortality during S. aureus bacteremia, whereas Th1 or Th17 responses are essential for prevention of S. aureus skin abscesses and the clearance of bacteria from the GI tract. Both antibody- and T-cell-mediated mechanisms contribute to prevention of S. aureus dermonecrosis. Engagement of all three immune pathways results in the most robust protection under each pathological condition. Therefore, our results suggest that eliciting multipronged humoral and cellular responses to S. aureus antigens may be critical to achieve effective and comprehensive immune defense against this pathogen.IMPORTANCES. aureus is a leading cause of healthcare- and community-associated bacterial infections. S. aureus causes various illnesses, including bacteremia, meningitis, endocarditis, pneumonia, osteomyelitis, sepsis, and skin and soft tissue infections. S. aureus colonizes between 20 and 80% of humans; carriers are at increased risk for infection and transmission to others. The spread of multidrug-resistant strains limits antibiotic treatment options. Vaccine development against S. aureus has been unsuccessful to date, likely due to an inadequate understanding about the mechanisms of immune defense against this pathogen. The significance of our work is in illustrating the necessity of generating multipronged B-cell, Th1-, and Th17-mediated responses to S. aureus antigens in conferring enhanced and broad protection against S. aureus invasive infection, skin and soft tissue infection, and mucosal colonization. Our work thus, provides important insights for future vaccine development against this pathogen.

Antibody-mediated protection against Staphylococcus aureus dermonecrosis and sepsis by a whole cell vaccine.

Staphylococcus aureus is a very important human pathogen that causes significant morbidity and mortality worldwide. Several vaccine clinical trials based on generating antibody against staphylococcal surface polysaccharides or proteins have been unsuccessful. A killed whole cell lysate preparation (SaWCA) was made by lysing a USA 300 strain with lysostaphin followed by sonication and harvest of the supernatant fraction. Immunization with SaWCA and cholera toxin (CT) generated robust IL-17A but relatively modest antibody responses, and provided protection in the skin abscess but not in the dermonecrosis or invasive infection model. In contrast, parenteral immunization with SaWCA and alum produced robust antibody and IL-17A responses and protected mice in all three models. Sera generated after immunization with SaWCA had measurable antibodies directed against six tested conserved surface proteins, and promoted opsonophagocytosis activity (OPA) against two S. aureus strains. Passive transfer of SaWCA-immune serum protected mice against dermonecrosis and invasive infection but provided no demonstrable effect against skin abscesses, suggesting that antibodies alone may not be sufficient for protection in this model. Thus, immunization with a SA lysate preparation generates potent antibody and T cell responses, and confers protection in systemic and cutaneous staphylococcal infection models.

Identification of the Factors Responsible for the Selective in vitro Cytotoxic Activity of Isoprenylated Coumarin Derivatives under Nutrient-deprived Conditions.

Pancreatic cancer is one of the most devastating forms of human cancer. The lack of effective clinical treatments for pancreatic cancer has led to one of the lowest five-year survival rates among all cancers. Recently, our laboratory has developed a novel series of isoprenylated coumarin derivatives that have exhibited anti-pancreatic cancer activity exclusively under nutrient-deprived conditions. In this study, we report the effect of the various cell culture medium components on the preferential cytotoxicity of our lead isoprenylated coumarin compound against the pancreatic adenocarcinoma cell line PANC-1. In particular, our findings show a clear link between observed cytotoxicity and glucose deprivation, suggesting that our compound targets a salvage pathway when glycolysis is no longer an option for cancer cell survival. The cytotoxicity of our lead compound was also examined in vitro against two other pancreatic cancer cell lines, BxPC-3 and Capan-2 under both nutrient-rich and nutrient-deprived conditions.