Engineered cysteine antibodies: an improved antibody-drug conjugate platform with a novel mechanism of drug-linker stability.

Antibody-drug conjugates (ADCs) are fulfilling the promise of targeted therapy with meaningful clinical success. An intense research effort is directed towards improving pharmacokinetic profiles, toxicity and chemical stability of ADCs. The majority of ADCs use amide and thioether chemistry to link potent cytotoxic agents to antibodies via endogenous lysine and cysteine residues. While maleimide-cysteine conjugation is used for many clinical stage ADC programs, maleimides have been shown to exhibit some degree of post-conjugation instability. Previous research with site-directed mutagenic incorporation of cysteine residues for conjugation revealed that the stability of the drug-antibody linkage depends on the site of conjugation. Here we report on a collection of engineered cysteine antibodies (S239C, E269C, K326C and A327C) that can be site-specifically conjugated to potent cytotoxic agents to produce homogenous 2-loaded ADCs. These ADCs confirm that site of conjugation impacts maleimide stability and present a novel mechanism of thioether stabilization, effectively unlinking stability from either local chemical environment or calculated solvent accessibility and expanding the current paradigm for ADC drug-linker stability. These ADCs show potent in vitro and in vivo activity while delivering half of the molar equivalent dose of drug per antibody when compared to an average 4-loaded ADC. In addition, our lead engineered site shields highly hydrophobic drugs, enabling conjugation, formulation and clinical use of otherwise intractable chemotypes.

An in situ study of protein adsorption on combinatorial Cu-Al films using spectroscopic ellipsometry.

An approach to quantifying adsorbed protein layers at the protein/metal interface through spectroscopic ellipsometry using an in situ technique is described. A combinatorial binary Cu(1-x)Al(x) (0

Surface characteristics and protein adsorption on combinatorial binary Ti-M (Cr, Al, Ni) and Al-M (Ta, Zr) library films.

Systematic studies of protein adsorption onto metallic biomaterial surfaces are generally lacking. Here, combinatorial binary library films with compositional gradients of Ti(1-x)Cr(x), Ti(1-x)Al(x), Ti(1-x)Ni(x) and Al(1-x)Ta(x), (0

Human papilloma virus in squamous carcinoma of the head and neck: a study of cases in south east Scotland.

Several studies have found human papillomavirus virus (HPV) in tissue from head and neck squamous cell carcinomas (HNSCCs), although the number of positive cases varies greatly from study to study. The extent and molecular epidemiology of HPV in HNSCC were assessed within cases drawn from southeast Scotland by performing broad-spectrum, real-time HPV polymerase chain reaction (PCR) on DNA extracted from 100 cases of HNSCC in formalin-fixed, paraffin wax-embedded material. All HPV-positive specimens were genotyped and sampled by laser capture microdissection. Pure samples of tumour, and, where possible, dysplastic and normal epithelium were then submitted for further HPV PCR and genotyping to investigate the sensitivity of the technique in small tissue samples. 10 of 100 cases tested positive for HPV, with 8 of these being derived from Waldeyer's ring. HPV DNA was found in adjacent epithelium in two of four cases where this was available. These findings confirm that HPV is likely to be involved in a subset of HNSCC in this population and that successful amplification of HPV nucleic acid is possible even using small amounts of paraffin wax-embedded tissue.

Surgical management of head and neck malignancy.

More than 90% of head and neck tumours are squamous cell carcinomas. This review focuses on tumours arising from the mucosal surfaces of the upper aerodigestive tract. We discuss the aetiology, presentation and investigation of these tumours and give special attention to their management which may comprise surgical resection, chemoradiation or combined therapy. The surgical treatment of the clinically positive neck and the somewhat controversial topic of management of the N0 neck are also discussed.

Survival from accidental strangulation from a scarf resulting in laryngeal rupture and carotid artery stenosis: the "Isadora Duncan syndrome". A case report and review of literature.

In 1929 the dancer Isadora Duncan died from strangulation and carotid artery insult when her scarf caught in the wheels of a motor vehicle in which she was travelling. As part of the Edinburgh Festival scene, cycle propelled rickshaws are in popular use as short range taxis. The case is presented of a student who sustained a laryngeal rupture from strangulation with a scarf in the same way as Isadora. Despite an out of hospital cardiorespiratory arrest, severe laryngeal trauma, and carotid artery damage resulting in hemiparesis, the patient was successfully resuscitated and recovered with no neurological deficit. It is believed that this is the first recorded survival from this condition.

Uracil-initiated base excision DNA repair synthesis fidelity in human colon adenocarcinoma LoVo and Escherichia coli cell extracts.

The error frequency of uracil-initiated base excision repair (BER) DNA synthesis in human and Escherichia coli cell-free extracts was determined by an M13mp2 lacZ alpha DNA-based reversion assay. Heteroduplex M13mp2 DNA was constructed that contained a site-specific uracil target located opposite the first nucleotide position of opal codon 14 in the lacZ alpha gene. Human glioblastoma U251 and colon adenocarcinoma LoVo whole-cell extracts repaired the uracil residue to produce form I DNA that was resistant to subsequent in vitro cleavage by E. coli uracil-DNA glycosylase (Ung) and endonuclease IV, indicating that complete uracil-initiated BER repair had occurred. Characterization of the BER reactions revealed that (1) the majority of uracil-DNA repair was initiated by a uracil-DNA glycosylase-sensitive to Ugi (uracil-DNA glycosylase inhibitor protein), (2) the addition of aphidicolin did not significantly inhibit BER DNA synthesis, and (3) the BER patch size ranged from 1 to 8 nucleotides. The misincorporation frequency of BER DNA synthesis at the target site was 5.2 x 10(-4) in U251 extracts and 5.4 x 10(-4) in LoVo extracts. The most frequent base substitution errors in the U251 and LoVo mutational spectrum were T to G > T to A >> T to C. Uracil-initiated BER DNA synthesis in extracts of E. coli BH156 (ung) BH157 (dug), and BH158 (ung, dug) was also examined. Efficient BER occurred in extracts of the BH157 strain with a misincorporation frequency of 5.6 x 10(-4). A reduced, but detectable level of BER was observed in extracts of E. coli BH156 cells; however, the mutation frequency of BER DNA synthesis was elevated 6.4-fold.

Increased spontaneous mutation frequency in human cells expressing the phage PBS2-encoded inhibitor of uracil-DNA glycosylase.

The Ugi protein inhibitor of uracil-DNA glycosylase encoded by bacteriophage PBS2 inactivates human uracil-DNA glycosylases (UDG) by forming a tight enzyme:inhibitor complex. To create human cells that are impaired for UDG activity, the human glioma U251 cell line was engineered to produce active Ugi protein. In vitro assays of crude cell extracts from several Ugi-expressing clonal lines showed UDG inactivation under standard assay conditions as compared to control cells, and four of these UDG defective cell lines were characterized for their ability to conduct in vivo uracil-DNA repair. Whereas transfected plasmid DNA containing either a U:G mispair or U:A base pairs was efficiently repaired in the control lines, uracil-DNA repair was not evident in the lines producing Ugi. Experiments using a shuttle vector to detect mutations in a target gene showed that Ugi-expressing cells exhibited a 3-fold higher overall spontaneous mutation frequency compared to control cells, due to increased C:G to T:A base pair substitutions. The growth rate and cell cycle distribution of Ugi-expressing cells did not differ appreciably from their parental cell counterpart. Further in vitro examination revealed that a thymine DNA glycosylase (TDG) previously shown to mediate Ugi-insensitive excision of uracil bases from DNA was not detected in the parental U251 cells. However, a Ugi-insensitive UDG activity of unknown origin that recognizes U:G mispairs and to a lesser extent U:A base pairs in duplex DNA, but which was inactive toward uracil residues in single-stranded DNA, was detected under assay conditions previously shown to be efficient for detecting TDG.

Delayed DNA joining at 3' mismatches by human DNA ligases.

Repair synthesis catalysed by DNA polymerase beta at 1 nt gaps occurs in the main pathway of mammalian base excision repair. DNA polymerase beta has no exonucleolytic proof-reading ability, and exhibits high error frequency during DNA synthesis. Consequently, continuous correction of endogenous DNA damage by short-patch repair synthesis might lead to a high spontaneous mutation rate, unless subsequent steps in the repair pathway allow for selective removal of incorporation errors. We show here that both human DNA ligase I and III discriminate strongly between a correctly paired versus a mispaired residue at the 3' position of a nick in DNA, when assayed in the presence of physiological concentrations of KCl. The resulting delay in joining after misincorporation by DNA polymerase beta during gap filling could allow for removal of the mismatched terminal residue by a distinct 3' exonuclease.

Increased expression of CD40 on thymocytes and peripheral T cells in autoimmunity: a mechanism for acquiring changes in the peripheral T cell receptor repertoire.

CD40, a cell surface molecule found on B lymphocytes and other antigen presenting cells, can, when engaged by CD40 ligand (CD40L), induce gene rearrangements and isotype switching. We report here that CD40 is also expressed on thymocytes and on up to 50% of peripheral T cells from autoimmune prone strains of mice. In normal animals, CD40 is present on a small population of T cells and thymocytes. CD40 is expressed on most T cell hybridomas. We demonstrate that CD40 engagement on peripheral T cells, T cell hybridomas and thymocytes results in altered TCRValpha expression. That induced expression of different Valpha's results from the activity of the recombinase gene is implied by the observation that CD40 does not induce TCR changes in RAG knock-out mice. Total cell numbers remained unchanged between anti-CD40 treated and untreated populations of thymocytes or T cells indicating that treatment does not induce cell proliferation or cell death. The data presented here suggest a mechanism by which self reactive T cells accumulate peripherally and independently of selective processes of the thymus.

Management of inverted papilloma via Denker's approach.

Denker's approach was used in the management of 78 patients presenting with an inverted papilloma of the nasal sinus complex between the years 1986 and 1993 at the University Teaching Hospital in Rotterdam. The recurrence rate was 9% with a mean follow-up after surgery of 56 months. There was minimal morbidity and no mortality associated with the procedure. Three patients had a squamous cell carcinoma associated with the inverted papilloma. The results of our study indicate that Denker's approach has a similar or lower recurrence rate than an open external approach to papilloma and is a safe procedure with minimal morbidity.

Fidelity and mutational specificity of uracil-initiated base excision DNA repair synthesis in human glioblastoma cell extracts.

The fidelity of DNA synthesis associated with uracil-initiated base excision repair was measured in human whole cell extracts. An M13mp2 lacZalpha DNA-based reversion assay was developed to assess the error frequency of DNA repair synthesis at a site-specific uracil residue. All three possible base substitution errors were detected at the uracil target causing reversion of opal codon 14 in the Escherichia coli lacZalpha gene. Using human glioblastoma U251 whole cell extracts, approximately 50% of the heteroduplex uracil-containing DNA substrate was completely repaired, as determined by the insensitivity of form I DNA reaction products to cleavage by a combined treatment of E. coli uracil-DNA glycosylase and endonuclease IV. The majority of repair occurred by the uracil-initiated base excision repair pathway, since the addition of the bacteriophage PBS2 uracil-DNA glycosylase inhibitor protein to extracts significantly blocked this process. In addition, the formation of repaired form I DNA molecules occurred concurrently with limited DNA synthesis, which was largely restricted to the HinfI DNA fragment initially containing the uracil residue and specific to the uracil-containing DNA strand. Based on the reversion frequency of repaired M13mp2 DNA, the fidelity of DNA repair synthesis at the target was determined to be about one misincorporated nucleotide per 1900 repaired uracil residues. The major class of base substitutions propagated transversion mutations, which were distributed almost equally between T to G and T to A changes in the template. A similar mutation frequency was also observed using whole cell extracts from human colon adenocarcinoma LoVo cells, suggesting that mismatch repair did not interfere with the fidelity measurements.

The effects of alcohol and smoking upon the age, anatomic sites and stage in the development of cancer of the oral cavity and oropharynx in females in the south west Netherlands.

A retrospective review of 303 women, aged 40 or over, with squamous cell carcinomas of the oral cavity or oropharynx was conducted in the south-west Netherlands to study the effects of smoking and alcohol upon the age of onset, site and stage of disease. It was noted that patients presenting with oropharyngeal cancers were younger and had a higher incidence of smoking and history of heavy drinking. Age at presentation was also affected by the amount of alcohol and tobacco consumed with non-users presenting with tumors approximately 15 years later. A specific finding was that heavy drinkers and smokers tended to present with late-stage-disease.

The influence of alcohol and smoking on the incidence of oral and oropharyngeal cancer in women.

A retrospective case reference study examining the use of alcohol and tobacco in 303 women aged 40 or over suffering from oral or oropharyngeal cancer was conducted in the south-west Netherlands. Both alcohol and tobacco consumption are important in the development of oral and oropharyngeal cancer with increased consumption of both markedly increasing the risks of cancer, but alcohol having the greater effect.

Identification of specific carboxyl groups on uracil-DNA glycosylase inhibitor protein that are required for activity.

The bacteriophage PBS2 uracil-DNA glycosylase inhibitor (Ugi) protein inactivates uracil-DNA glycosylase (Ung) by forming an exceptionally stable protein-protein complex in which Ugi mimics electronegative and structural features of duplex DNA (Beger, R. D., Balasubramanian, S., Bennett, S. E., Mosbaugh, D. W., and Bolton, P. H. (1995) J. Biol. Chem. 270, 16840-16847; Mol, C. D., Arvai, A. S., Sanderson, R. J., Slupphaug, G., Kavli, B., Krokan, H. E., Mosbaugh, D. W., and Tainer, J. A. (1995) Cell 82, 701-708). The role of specific carboxylic amino acid residues in forming the Ung.Ugi complex was investigated using selective chemical modification techniques. Ugi treated with carbodiimide and glycine ethyl ester produced five discrete protein species (forms I-V) that were purified and characterized. Analysis by mass spectrometry revealed that Ugi form I escaped protein modification, and forms II-V showed increasing incremental amounts of acyl-glycine ethyl ester adduction. Ugi forms II-V retained their ability to form a Ung.Ugi complex but exhibited a reduced ability to inactivate Escherichia coli Ung, directly reflecting the extent of modification. Competition experiments using modified forms II-V with unmodified Ugi as a competitor protein revealed that unmodified Ugi preferentially formed complex. Furthermore, unmodified Ugi and poly(U) were capable of displacing forms II-V from a preformed Ung.Ugi complex but were unable to displace Ugi form I. The primary sites of acyl-glycine ethyl ester adduction were located in the alpha2-helix of Ugi at Glu-28 and Glu-31. We infer that these two negatively charged amino acids play an important role in mediating a conformational change in Ugi that precipitates the essentially irreversible Ung/Ugi interaction.

Crystal structure of human uracil-DNA glycosylase in complex with a protein inhibitor: protein mimicry of DNA.

Uracil-DNA glycosylase inhibitor (Ugi) is a B. subtilis bacteriophage protein that protects the uracil-containing phage DNA by irreversibly inhibiting the key DNA repair enzyme uracil-DNA glycosylase (UDG). The 1.9 A crystal structure of Ugi complexed to human UDG reveals that the Ugi structure, consisting of a twisted five-stranded antiparallel beta sheet and two alpha helices, binds by inserting a beta strand into the conserved DNA-binding groove of the enzyme without contacting the uracil specificity pocket. The resulting interface, which buries over 1200 A2 on Ugi and involves the entire beta sheet and an alpha helix, is polar and contains 22 water molecules. Ugi binds the sequence-conserved DNA-binding groove of UDG via shape and electrostatic complementarity, specific charged hydrogen bonds, and hydrophobic packing enveloping Leu-272 from a protruding UDG loop. The apparent mimicry by Ugi of DNA interactions with UDG provides both a structural mechanism for UDG binding to DNA, including the enzyme-assisted expulsion of uracil from the DNA helix, and a crystallographic basis for the design of inhibitors with scientific and therapeutic applications.