Chemistry: natural resins or derivatives; peptides or proteins; – Proteins – i.e. – more than 100 amino acid residues – Glycoprotein – e.g. – mucins – proteoglycans – etc.
Reexamination Certificate
1995-06-01
2001-04-24
Johnson, Nancy A. (Department: 1642)
Chemistry: natural resins or derivatives; peptides or proteins;
Proteins, i.e., more than 100 amino acid residues
Glycoprotein, e.g., mucins, proteoglycans, etc.
C530S300000, C530S328000, C530S330000, C530S350000, C530S388800
Reexamination Certificate
active
06222020
ABSTRACT:
The present invention relates to DNA probes for detecting a tandemly-repeated nucleotide sequence in the gene encoding mucin glycoprotein expressed by human mammary epithelial cells, to the use of the probe in diagnosis and in “fingerprinting” individuals, to the polypeptides expressed by the corresponding mucin gene, to antibodies against the polypeptides and to the use of the polypeptides and antibodies in the diagnosis and therapeutic treatment of cancer.
Normal and malignant human mammary epithelial cells express high molecular weight glycoproteins (gps) which are extensively glycosylated and very antigenic. As a result, many of the monoclonal antibodies (MAbs) selected for reactivity with human breast cancer and other carcinomas are found to react with molecules which are produced in abundance by the fully differentiated human mammary tissue and are found in the milk fat globule (MFG) and in milk. However, the level of expression of a particular antigenic determinant may be different in the gps produced by the normal differentiated cell and in the similar molecules produced by breast cancers. This means that some antibodies can show a certain specificity for reacting with tumour gps.
The molecules bearing the epitopes recognised by these antibodies are complex and have been difficult to analyse, both because they are large and heavily glycosylated (>250,000 daltons) and because of the complex pattern of expression. Two of the MAbs, HMFG-1 and -2, react with a component in human milk which appears to be greater than 400,000 daltons, whereas the molecules found in sera and tumours are smaller, although the dominant components are still greater then 200,000 daltons on immunoblots. The large glycoprotein produced by the differentiated mammary epithelial cells found in human milk or in the milk fat globule has been purified and shown to have some of the characteristics of the mucins. This component contains a large amount of carbohydrate joined in O-linkage to serine and threonine residues via the linkage sugar N-acetylgalactosamine. Moreover, the core protein contains high levels of serine, threonine and proline and low levels of aromatic and sulphur containing amino acids.
These mucin-like glycoproteins are also secreted by a number of other normal epithelial cells. The monoclonal antibody HMFG-1 is highly reactive with the milk mucin and evidence suggests that the epitope recognised by this antibody is more abundant on the fully processed mucin, characteristic of normal differentiation.
In tumours, the molecular weight of the molecules carrying these antigenic determinants differs among individual tumours and, in the case of the components recognised by the HMFG-2 antibody, can range from 80-400K daltons. Although it appears that the differences observed in the mobility of the high molecular weight bands are due to genetic polymorphism this probably does not explain variations in the size of the lower bands. It has been proposed that these may be the result of aberrant processing occurring in the tumour cell possibly within the glycosylation pathways.
For the majority of the monoclonal antibodies reacting with this group of molecules the exact nature of the antigenic epitopes remains unclear but circumstantial evidence has suggested that carbohydrate may at least be partly involved in many of the epitopes. Moreover, from previously available data it was not known whether the mucin found in the normal differentiated cells, and that observed in the tumours, contain the same core protein, or just carry common carbohydrate determinants.
Mucin has now been isolated from human milk by affinity chromatography enabling identification of the core protein and the gene encoding the protein. This has been found to be a highly polymorphic gene defined by the peanut urinary mucin (PUM) locus [see Swallow et al.,
Disease Markers,
4, 247, (1986) and
Nature,
327, 82-84 (1987)]. The gene product, which is hereafter referred to as human polymorphic epithelial mucin or HPEM, has been detected in breast tumours and other carcinomas as well as in some normal epithelial tissues.
It has now been found that the HPEM core protein has epitopes which also appear in the aberrantly processed gps produced by adenocarcinoma cells. Certain of these epitopes are not exposed in the fully processed mucin glycoprotein produced by the lactating mammary gland.
In one aspect the present invention therefore provides an antibody against a human mucin core protein which antibody substantially does not react with a fully processed human mucin glycoprotein.
As used herein the term “antibody” is intended to include fragments of antibodies bearing antigen binding sites such as the F(ab′)
2
fragments.
Antibodies according to the present invention react with HPEM core protein, especially as expressed by colon, lung, ovary and particularly breast carcinomas, but have reduced or no reaction with the corresponding fully processed HPEM. In a particular aspect the antibodies react with HPEM core protein but not with fully processed HPEM glycoprotein as produced by the normal lactating human mammary gland.
Antibodies according to the present invention have no significant reaction with the mucin glycoproteins produced by pregnant or lactating mammary epithelial tissues but react with the mucin proteins expressed by mammary epithelial adenocarcinoma cells. These antibodies show a much reduced reaction with benign breast tumours and are therefore useful in the diagnosis and localisation of breast cancer as well as in therapeutic methods.
The antibodies may be used for other purposes including screening cell cultures for the polypeptide expression product of the human mammary epithelial mucin gene, or fragments thereof, particularly the nascent expression product. In this case the antibodies may conveniently be polyclonal or monoclonal antibodies.
Antibodies according to the present invention may be produced by innoculation of suitable animals with HPEM core protein or a fragment thereof such as the peptides described below. Monoclonal antibodies are produced by the method of Kohler & Milstein (Nature 256, 495-497/1975) by immortalising spleen cells from an animal innoculated with the mucin core protein or a fragment thereof, usually by fusion with an immortal cell line (preferably a myeloma cell line), of the same or a different species as the innoculated animal, followed by the appropriate cloning and screening steps.
In a particular aspect the present invention provides the monoclonal antibodies designated SM3 against the HPEM core protein. In another aspect the invention provides the hybridoma cell line which secretes the antibodies SM3 and has been designated HSM3. Samples of HSM3 have been deposited with ECACC (Public Health Laboratory Service, Centre for Applied Microbiology and Research, ECACC, Porton Down, Salisbury, Wilts, England) on Jan. 7, 1987 under accession number 87010701.
Using antibodies according to the invention it has been possible to screen a phage library constructed from mRNA isolated from a human breast cancer cell line to identify sequences coding for portions of the mucin core protein. Complementary DNA sequences have been constructed and from these it has surprisingly been found that the gene encoding the core protein contains multiple tandem repeats of a 60 base sequence leading to considerable polymorphism sufficiently extensive that cDNA fragments corresponding to the repeat sequence would be useful for fingerprinting DNA. The fingerprinting thus made possible has applications in for instance ascertaining whether bone marrow growth after transplants is from the host or the donor and in forensic medicine for identifying individuals using body tissues or fluids.
Accordingly the present invention also provides a nucleic acid fragment comprising at least 17 nucleotide bases the fragment being hybridisable with at least one of
a) the DNA sequence
5′ &e
Burchell Joy
Gendler Sandra
Taylor-Papadimitriou Joyce
Cooper Iver P.
Imperial Cancer Research Technology Limited
Johnson Nancy A.
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