the invention will be described by way of example only with reference to cellular immunogens , as the preferred embodiment of the invention . if the essential components of the immunogen are used in a cell - free form , they may be obtained by techniques known to these of ordinary skill in the art . the cells used in the present invention may be described as cellular immunogens . they can be made by taking a suitable cell line ( eg . mrc - 5 , hela cells , vero cells , etc .) or fresh human cells ( eg . umbilical cord cells ), and transforming them ( for example by using a retrovirus vector , calcium phosphate precipitation or electroporation ) with a suitable oncogene , preferably with a strong promoter for the gene ( see barbacid ( 1987 ) and below ). selection of the resulting transfected cells may be by cell transformation ( for example ras - transformed cells have a transformed phenotype and usually outgrow untransformed cells , at least in the mouse ) or co - selection of a selectable marker ( eg . neo ) probably followed by cloning and screening . alternatively , if available , cells already containing a suitable oncogene may be used . the cells may also bve transformed with additional mutated antigen ( s ), or tumour - specific transplantation antigen ( a developmental or differentiation antigen ). the cells that may be used in the invention comprise those that contain genes for mhc molecules that are foreign with respect to the mhc molecules of the mammal . they include primary cells , primary cell lines , cell lines kept under pathogen - free conditions , such as cell lines derived for the purpose of growing viruses for vaccine purposes ( e . g . mrc - 5 or a more ethical equivalent or replacement ), established cell lines kept under pathogen - free conditions ( again , for example , cell lines derived for the purpose of growing viruses for vaccine purposes ) and tumour cells . another example is a cell that is manufactured to express a foreign mhc antigen molecule . the cells may be allogeneic or xenogeneic . in certain cases , it may be preferred that the cells are human cells . certain established cell lines would not be suitable as live vaccines , unless they were ‘ cleaned up ’ and certified safe for vaccine purposes first ( e . g . hela cells , hl 60 cells ) ( see who technical report series ( 1987 ) volume 747 , 93 - 107 and 1994 , volume 840 , 100 - 201 , who , geneva ). the genetic information added to the cells may be for a viral oncogene or a cellular oncogene . tumour suppressor genes may also be used . the oncogenes that can be used include k - ras , h - ras and n - ras , with point mutations in codon 12 or 13 . for example , amino acid 12 may be changed from gly to val , ser , arg , cys , asp , ala or any other amino acid , or amino acid 13gly to asp . mutations at position 61 can also be used . alternative constructs that include the region encoding the mutated amino acid , with or without additional amino acid sequences , may be used . for example , a gene encoding the first 20 amino acids of a mutated k - ras , followed by the amino acids of il 2 , il 12 or ifn gamma may be used . the genes are not restricted to those having the naturally - occurring codons for these amino acids or peptides . other oncogenes include p53 , where mutations often involve deletions . here the gene used to produce an effective vaccine is expected to require the region encompassing the mutation . the same applies for fusion genes , e . g . p210 bcr - abl . non - mutated but still antigenic regions of some oncogenes may also be used . to elicit the correct immune response , the oncogenes in the cells must be from the same class as the tumour - associated oncogene in the mammal , i . e . if the tumour contains a k - ras oncogene , then the cells administered to the patient should also contain a gene or peptide corresponding to an immunogenic region of a k - ras oncogene . more accurately , it is the expression product of the oncogene that will be immunogenic ; however , it is preferred that the cells comprise the oncogene , enabling expression of the product in vitro or in vivo . it is not necessary for the oncogene in the cells to be derived directly from the tumour in the mammal . additional oncogenes from the same or a different class may also be present in the cells . other genes that might be present in the cells include genes that are helpful in generating the cell line ( e . g . selection markers ), suicide genes ( e . g . hsvtk for use with gangciclovir which may be valuable for providing even more safety when immunising with live cells ) and genes for immune molecules ( e . g . strong antigens such as hb core antigen ; antigen - presenting molecules such as b7 ; or lymphokines such as il 12 , gamma interferon ). the cells may be killed prior to administration , e . g . by irradiation or mitomycin c treatment . however , since the cells used in this invention are , as far as is practicable and necessary for vaccine purposes , pathogen - free and also express foreign mhc molecules , they can be administered as live ( i . e . replication - competent ) cells . the cellular immunogen may be used prophylactically , post - surgery to prevent relapse , in conjunction with another treatment , or on its own to provide effective treatment of tumours . the amount of immunogen that is required for effective treatment can readily be determined by one of ordinary skill in the art , as may types of formulation for administration , by vaccination . c3h 10t½ ( reznikoff et al ( 1973 ) cancer res . 33 , 3231 ; h - 2 k haplotype ) and balb / c3t3 ( aaronson and todaro ( 1968 ) j . cell physiol . 72 , 141 ; h - 2 d haplotype ) fibroblasts were obtained from the american type culture collection ( atcc , rockville , md .). cells were transfected with ψ2 packaged v - ki - ras - containing ki - musv as described previously ( maudsley and morris , 1998 , j . exp . med . 167 , 706 - 711 ) producing c3h 201 and ki - balb / c respectively . an ej - ha - ras - transformed derivative of c3h 10t½ ( ej - 10t½ ) was produced by co - transfecting 5 × 10 5 cells with 30 μg pej6 . 6 ( 1982 , cell , 29 , 161 ) and 10 μg psv2neo ( 1982 , j . mol . appl . genet ., 1 , 327 ) by calcium phosphate precipitation followed by selection in geneticin . c3h 10t½ cells transformed with v - ha - ras ( v - ha - 10t½ ) were derived by infecting c3h 10t½ cells with ψ2 - packaged ( i . e . helper virus - free ) retroviral vector containing the oncogene co - linear with the selection marker neo , followed by selection in geneticin . c3h 201 and ej - 10t½ are both highly tumorigenic in c3h / he mice with similar tumorigenicity : typically 10 6 cells give tumours in 100 % of mice and 10 5 cells in approximately 90 % of mice . ha - 10t½ cells were less tumorigenic . male , 6 - 8 week old c3h / he mice were either injected with 10 6 live ki - balb / c cells subcutaneously ( s . c . ), left unimmunised or immunised with ha - 10t½ cells . after 2 weeks mice were challenged with 10 6 c3h 201 cells subcutaneously or 10 6 ej - 10t½ cells injected s . c . in the flank . the mice were monitored regularly for tumour growth and were humanely killed before there was any risk of their suffering and not later than when the tumour reached 25 mm in diameter . the results of the experiments are shown in table 1 . 10 6 c3h 201 and ej - 10t½ cells injected s . c . produced tumours in all unimmunised and ha - 10t½ cell immunised mice as expected . these tumours grew progressively . ej - 10t { fraction ( 1 / 2 )} cells produced tumours also in nice immunised with ki - balb / c . surprisingly , only 2 out of 10 c3h / he mice immunised with ki - balb / c cells and challenged with c3h 201 grew tumours at any time , and these were small and regressed . these tumours disappeared within 4 weeks . these results are surprising , since it was assumed that the oncoprotein must be presented to the mouse &# 39 ; s immune system by self mhc antigens ( h - 2 k ) and the ki - balb / c cells are of the h - 2 d haplotype . this approach appears to be effective in preventing the growth of highly tumorigenic cells in laboratory mice .
a cancer immunogen comprises foreign mhc molecules and additionally one or more oncognes which can be used to immunize against tumors containing the same or similar oncogenes . where pathogen - free allogeneic cells are used , it may not be necessary to kill the vaccine before it is administered . the efficacy of the vaccine may be enhanced if the cells also contain immunoenhancing molecules , tumor antigens , or third - party antigens . cell vaccines containing oncongens can be standardized and used to treat specific cancers where there are analogous oncongenes in the tumor or pre - cancerous cells . a panel of such cells covering different oncogenes may be used . the vaccines can be used to immunize prophylactically , in conduction with other therapy , post - surgery or on their own .