George H. O'Brien, Jr. VA Medical Center

Prostate-specific membrane antigen (PSMA), a type II transmembrane protein, was originally thought to be strictly expressed in prostatic tissue, but recent studies have demonstrated PSMA protein expression in nonprostatic tumor neovasculature as well. Using immunohistochemistry, reverse transcription-PCR assays, and in situ hybridization, we have demonstrated PSMA mRNA transcripts and protein expression in the endothelium of tumor-associated neovasculature of multiple nonprostatic solid malignancies. In addition, we found no PSMA mRNA or protein expression in the vascular endothelial cells of corresponding benign tissue examples. Our findings expand the possible therapeutic role of PSMA and establish it as a unique biomarker specifically produced and expressed by tumor-associated neovasculature but not produced or expressed by normal vessels.

The plasminogen activator inhibitor type 1 (PAI-1) gene encodes the physiological inhibitor of tissue-type and urokinase-type plasminogen activators and is induced by cytokines such as transforming growth factor-beta (TGF-beta). Studies have identified DNA sequence elements within the first 1.3 kb of the 5'-upstream DNA that mediate cytokine responsiveness in transfected cells in vitro. However, the DNA sequences that mediate PAI-1 expression in vivo have not yet been delineated. To define these regulatory sequences, we generated transgenic mice that expressed a hybrid gene comprising sequences between -1,272 and +75 of the human PAI-1 gene ligated to a LacZ reporter gene. Transgene expression detected in two independent lines was observed only in kidney from embryonic day 13 to adult and was seen primarily in proximal tubule cells of the outer medulla. Transgene expression and activity were unchanged in response to TGF-beta and remained restricted to kidney. Thus we have identified a promoter region within the PAI-1 gene that targets transgene expression to kidney but, unlike the native promoter, is unresponsive to TGF-beta in the experimental protocol used.

Conventional electrical hull penetrators for deep-submersible applications employing pressure-resistant construction become prohibitively heavy when designed for reliable operation at 20,000 ft depth. Outboard cable assemblies employing conventional helical-lay conductors with a heavy rubber jacket and attached to the back shell of pressure-proof electrical connectors by rubber-molding or similar techniques have been shown to be extremely short-lived and very unreliable when subjected to a relatively small number of typical pressure cycles. A solution to both of these problems has been found in utilization of oil-filled pressure-compensation construction. While the weight saving for the cable assemblies is not so spectacular, the tremendous improvement in reliability along with substantial increase in versatility and ease of manufacture and installation makes the new approach attractive to designers of deep-submergence vehicles. The units described in this paper were developed for use on the Westinghouse Deep Star 20,000 vehicle. The electrical hull penetrators can each accommodate up to 11 external cables each containing 9 #16 AWG conductors. Extensive environmental testing has been accomplished and is described.