The proteasome inhibitor PS-341 markedly enhances sensitivity of multiple myeloma tumor cells to chemotherapeutic agents.

Increased nuclear factor kappaB (NF-kappaB) activity is associated with increased tumor cell survival in multiple myeloma. The function of NF-kappaB is inhibited through binding to its inhibitor, IkappaB. Release of activated NF-kappaB follows proteasome-mediated degradation of IkappaB resulting from phosphorylation of the inhibitor and, finally, conjugation with ubiquitin. We report that myeloma cells have enhanced IkappaBalpha phosphorylation and increased NF-kappaB activity compared with normal hematopoietic cells. The proteasome inhibitor PS-341 blocked nuclear translocation of NF-kappaB, blocked NF-kappaB DNA binding, and demonstrated consistent antitumor activity against chemoresistant and chemosensitive myeloma cells. The sensitivity of chemoresistant myeloma cells to chemotherapeutic agents was markedly increased (100,000-1,000,000-fold) when combined with a noncytotoxic dose of PS-341 without affecting normal hematopoietic cells. Similar effects were observed using a dominant negative super-repressor for IkappaBalpha. Thus, these results suggest that inhibition of NF-kappaB with PS-341 may overcome chemoresistance and allow doses of chemotherapeutic agents to be markedly reduced with antitumor effects without significant toxicity.

Comparative anatomy of the paratympanic organ (vitali organ) in the middle ear of birds and non-avian vertebrates: focus on alligators, parakeets and armadillos.

The paratympanic organ (PTO) in the middle ear has been described in numerous bird species, but little is known about the distribution of this presumed lateral line remnant in other vertebrate classes. Here we provide evidence for a PTO in juvenile alligators, and make the first detailed description of its location and relation to ligaments in the reptilian middle ear. The alligator PTO measures about 450 micro m in diameter. The alligator PTO contains hair cells whose cilia extend into a mucous substance within the lumen. The PTO connects though a ligament to the ear drum, suggesting that pressure onto the tympanic membrane might induce fluid movement in the PTO. Labeling of innervating nerve fibers with the fluorescent dye, DiI, indicates that the alligator PTO is connected with the vestibular brainstem. Because all bird species examined possess a PTO except for owls and possibly parakeets, we verified the absence of a PTO in parakeets by examination of serial sections combined with GABA immunolabeling for potential hair cells. Bird species with significant upper beak movement lack a PTO, suggesting that PTO function is incompatible with upper beak movement. We also examined the middle ear of an armadillo, a mammal that has a very basal position within the eutherian phylogenetic tree. A small vesicle with ciliated cells was found, but did not label with a hair-cell specific marker, antibodies to myosin VIIa, and thus is not likely to represent a true PTO. Our evidence for a PTO in a non-avian species, the alligator, together with previous reports suggesting the presence of a PTO in some mammals, indicates that ancestral stem amniotes possessed a PTO, and that the PTO was not a de novo invention of birds.