Fluoromethylglyoxal in the presence of glutathione has been shown to undergo a novel glyoxalase I-catalyzed product partitioning to S-fluorolactoylglutathione and S-pyruvylglutathione with fluoride elimination. While the partition ratio (fluoride eliminated/total fluoride) was insensitive to pH 5.5-7.5 and concentrations of substrate and glyoxalase I, it was species-dependent. When [1-2H]fluoromethylglyoxal was reacted with glyoxalase I, an increase in the partition ratio and retention of deuterium in the product fluorolactate was observed. This result can only be explained by a selective primary isotope effect on the protonation of an enediol intermediate relative to fluoride elimination.
Abstract Inkubation der Ketoaldehyde (I) mit Glutathion (II) und Glyoxalase I (GX I) liefert in schneller Reaktion die Thioester (III), die mit Glyoxalase II (GX II) unmittelbar zu den α‐Hydroxysauren (IV) hydrolysiert werden.
The protocatechuate and catechol pathways, two separate and parallel branches of the ..beta..-ketoadipate pathway in Pseudomonas putida, converge at a common intermediate - ..beta..-ketoadipate enol-lactone. The enol-lactone is generated by 4-carboxymuconolactone decarboxylase in the protocatechuate pathway while muconolactone isomerase produces it in the catechol pathway. The presence of these enzymes as well as ..beta..-carboxymuconate cycloisomerase and its substrate, ..beta..-carboxy-cis,cis-muconate, in a NMR tube, leads to the following sequence of events. Lactonization of ..beta..-carboxy-cis,cis-muconate produces 4-carboxymuconolactone which decarboxylates enzymatically with deuteration by D/sub 2/O to afford 2-(/sup 2/H)-4-ketoadipate enol-lactone - the substrate for muconolactone isomerase. Further conversion of the monodeuterated enol-lactone by muconolactone isomerase affords muconolactone which is nearly completely deuterated at the 4 position. The proton ricochets between the 2 and 4 positions with concurrent washout while in the 2 position. Based on the known absolute stereochemistry of 4-carboxymuconolactone and muconolactone, these results suggest that both the decarboxylase and isomerase proceed by syn mechanisms, but operate on opposite faces of the common enol-lactone substrate.
The potential of immunoconjugates of cytotoxic drugs for the treatment of cancer has not yet been realized owing to the difficulty of delivering therapeutic concentrations of these drugs to the target cells. In an effort to overcome this problem we have synthesized maytansinoids that have 100- to 1000-fold higher cytotoxic potency than clinically used anticancer drugs. These maytansinoids are linked to antibodies via disulfide bonds, which ensures the release of fully active drug inside the cells. The conjugates show high antigen-specific cytotoxicity for cultured human cancer cells (50% inhibiting concentration, 10 to 40 pM), low systemic toxicity in mice, and good pharmacokinetic behavior.
Postmenopausal hyperandrogenism with overt clinical effects is rare and often related to ovarian stromal disorders. We present a clinicopathologic study of 4 cases. The patients (age range 41–75 years; mean 62 years) had evidence of hirsutism or frank virilization. Their serum testosterone was elevated with or without increases in their serum androstenedione and DHEA levels. There were two right-ovarian hilus cell tumors, one associated with left-ovarian stromal hyperplasia and the other with bilateral hyperthecosis and nodular hilus cell hyperplasia. The other tumor was a small corticomedullary stromal luteoma with bilateral hyperthecosis and nodular hilus cell hyperplasia. The fourth patient had bilateral hilus cell hyperplasia with mild cortical-stromal hyperplasia. All these patients had rapid normalization of androgen levels after surgery without recurrence after a 2- to 10-year follow-up.
Bis-indolyl-(seco)-1,2,9a-tetrahydrocyclopropa[c]benz[e]indol-4-on e compounds are synthetic analogues of CC-1065 that are highly cytotoxic toward a broad spectrum of tumor cell lines. One of these compounds, called DC1, was conjugated to antibodies via novel cleavable disulfide linkers. Conjugates of DC1 with murine mAbs anti-B4 and N901 directed against tumor-associated antigens CD19 and CD56, respectively, proved to be extremely potent and antigen selective in killing target cells in culture. DC1 conjugates with humanized versions of anti-B4 and N901 antibodies were also constructed and demonstrated to be as cytotoxic and selective as the respective murine antibody conjugates. The anti-B4-DC1 conjugate showed antitumor efficacy in an aggressive metastatic human B-cell lymphoma survival model in SCID mice and completely cured animals hearing large tumors. Anti-B4-DC1 was considerably more effective in this tumor model than doxorubicin, cyclophosphamide, etoposide, or vincristine at their maximum tolerated doses.
The maytansinoid drug DM1 is 100- to 1000-fold more cytotoxic than anticancer drugs that are currently in clinical use. The immunoconjugate C242-DM1 was prepared by conjugating DM1 to the monoclonal antibody C242, which recognizes a mucin-type glycoprotein expressed to various extents by human colorectal cancers. C242-DM1 was found to be highly cytotoxic toward cultured colon cancer cells in an antigen-specific manner and showed remarkable antitumor efficacy in vivo. C242-DM1 cured mice bearing subcutaneous COLO 205 human colon tumor xenografts (tumor size at time of treatment 65-130 mm3), at doses that showed very little toxicity and were well below the maximum tolerated dose. C242-DM1 could even effect complete regressions or cures in animals with large (260- to 500-mm3) COLO 205 tumor xenografts. Further, C242-DM1 induced complete regressions of subcutaneous LoVo and HT-29 colon tumor xenografts that express the target antigen in a heterogeneous manner. C242-DM1 represents a new generation of immunoconjugates that may yet fulfill the promise of effective cancer therapy through antibody targeting of cytotoxic agents.
