Split central venous sampling of parathyroid hormone: an adjunct to surgical exploration.

BACKGROUND: Minimally invasive parathyroid surgery mandates preoperative localization of the adenoma for a targeted operative approach. This technique uses split internal jugular vein parathyroid hormone (PTH) samples to determine a gradient that then directs the surgical exploration. METHODS: Blood samples were drawn low in the neck from the jugular veins after the neck was opened. The p values for the difference in PTH between the right and left internal jugular veins were calculated with independent sample t tests. RESULTS: For left-sided adenomas, the left internal jugular vein mean was significantly higher than the right p = .001). For right-sided adenomas, the right internal jugular vein mean was significantly higher than the left (p = .004). In hyperplasia, there was no significant difference (p = .43). CONCLUSIONS: This study demonstrates the usefulness of split PTH internal jugular vein samples in patients in whom preoperative localization failed. Eighty percent of these patients with a gradient were treated with site-directed unilateral exploration.

Comparison of three different targeted tissue factor fusion proteins for inducing tumor vessel thrombosis.

Tissue Factor (TF) is a cell membrane receptor protein that is the initiator of the extrinsic pathway of the blood coagulation cascade and normally released from damaged tissues. By substituting the attachment site with a tumor delivery agent, this potent thrombogenic protein in its truncated form (tTF) can be targeted to the tumor where it can initiate clotting, thereby occluding the tumor's blood supply and causing rapid tumor destruction. To test the therapeutic potential of this vascular targeting approach, three fusion proteins, chTNT-3/tTF, chTV-1/tTF, and RGD/tTF, which target DNA exposed in degenerative areas of tumors, fibronectin on the tumor vascular basement membrane, and alpha nu beta 3 on the luminal side of tumor vessels, respectively, were developed and tested for their antitumor effects. Antigen binding and clotting assays demonstrated that each of the fusion proteins retained their antigen binding and thrombogenic activities. In vivo studies in mice bearing established MAD109 lung and Colon 26 carcinomas revealed that all three reagents induced histological evidence of microregional thrombosis and massive cell necrosis. Of interest, the chTV-1/tTF and RGD/tTF fusion proteins induced thrombosis in small and medium sized tumor vessels, whereas the chTNT-3/tTF induced clotting in relatively larger vessels. Treatment studies showed that chTNT-3/tTF and chTV-1/tTF but not RGD/tTF had a significant inhibition of tumor growth. These studies demonstrate that multiple targets exist which can be used to localize tTF to occlude tumor vessels in two diversely different murine tumor models. To attain a significant antitumor effect, however, these thrombogenic agents had to occlude medium and large vessels within the tumor. Additional studies are warranted to identify maximal conditions for inducing therapeutic vascular coagulation as a new and potent method of cancer therapy.

Pharmacokinetic characteristics and biodistribution of radioiodinated chimeric TNT-1, -2, and -3 monoclonal antibodies after chemical modification with biotin.

To improve the clinical potential of monoclonal antibodies (MAbs), new methods are required to augment antibody uptake in the tumor while minimizing binding in normal tissues. Our laboratory has pioneered the use of chemical modification to accomplish this goal. Using three chimeric MAbs, chTNT-1, chTNT-2, and chTNT-3, which target solid tumors by binding to common antigens found in the central necrotic core, we now demonstrate the potential of chemical modification to improve the pharmacokinetic characteristics of these unique MAbs. To identify optimal modification conditions, TNT MAbs were reacted with biotin at various ratios and tested by clearance and biodistribution analyses. The biodistribution results revealed that the numbers of biotin molecules per MAb yielding optimal tumor uptake were 3:1 for chTNT-1, 5:1 for chTNT-2, and 8:1 for chTNT-3. Biotinylated MAbs were found to have faster whole body clearance times and better biodistribution profiles compared to unmodified antibodies. Although chTNT-2 showed only a modest improvement after biotinylation, biodistribution results indicated that this MAb had the highest uptake in tumor. By reducing the charge of the antibody molecule, chemical modification appears to be a useful method for improving the pharmacokinetics and biodistribution of TNT antibodies directed to the necrotic region of solid tumors.

Generation of human interferon gamma and tumor Necrosis factor alpha chimeric TNT-3 fusion proteins.

Studies have shown that cytokines can effectively treat solid tumors by a direct cytotoxic effect as well as by immunomodulation. Both human interferon gamma (IFNgamma) and tumor necrosis factor alpha (TNFalpha) have been used to treat a variety of colon carcinoma cell lines and tumors in patients. These cytokines, however, are dose limited by their toxicity and fast clearance rates when given intravenously. To improve their therapeutic value, we now report on the generation of two new fusion proteins consisting of human IFNgamma and TNFalpha genetically linked to the C-terminal portion of chTNT-3, a monoclonal antibody (MAb), which targets human solid tumors by binding to intracellular antigens exposed in degenerating cells associated with tumor necrosis. In vitro characterization studies demonstrate that both the IFNgamma and TNFalpha fusion proteins are able to maintain their binding affinity to antigen as well as their direct cytotoxic effect and immunomodulatory functions. When both fusion proteins are combined at optimal doses, they demonstrate a 30% direct cellular cytotoxicity of human colon carcinoma cells of which approximately 14% can be attributed to apoptosis. In vivo, these agents were studied for their pharmakocinetic clearance rates and their ability to target human colon carcinomas heterotransplanted in nude mice. The results of these studies show that, compared with chTNT-3 parental antibody, both fusion proteins have a substantially shorter whole body half-life, yet are able to target tumor in a similar manner. As each of these fusion proteins are cleared from the circulation and normal tissues, tumor-to-normal-tissues ratios rise demonstrating the retention of these reagents in tumor. The generation of long-acting and targeted human IFNgamma and TNFalpha antibody fusion proteins will enable investigators to study the role of these potent immunostimulatory cytokines in the treatment of human solid tumors.