The La autoantigen is a malignancy-associated cell death target that is induced by DNA-damaging drugs.
OBJECTIVE
To evaluate the La autoantigen as a target for specific monoclonal antibody (mAb) binding in dead cancer cells after use of DNA-damaging chemotherapy.


METHODS
In vitro studies of La-specific 3B9 mAb binding to malignant and normal primary cells with and without cytotoxic drug treatment were done using immunoblotting and flow cytometry. Chromatin-binding studies and immunofluorescence detection of gammaH2AX as a marker of DNA double-stranded breaks together with 3B9 binding assays were done to measure DNA damage responses. Incorporation of a transglutaminase 2 (TG2) substrate and TG2 inhibition were studied to measure protein cross-linking in dead cells.


RESULTS
La was overexpressed in human cancer cell lines with respect to normal primary cells. Within 3 h of the DNA-damaging stimulus, La became chromatin bound when it colocalized with gammaH2AX. Later, after the stimulus produced cell death, La-specific 3B9 mAb bound specifically and preferentially in the cytoplasm of dead cancer cells. Moreover, 3B9 binding to dead cancer cells increased with increasing DNA damage. Both La and 3B9 became cross-linked in dead cancer cells via TG2 activity.


CONCLUSIONS
La autoantigen represents a promising cancer cell death target to determine chemotherapy response because its expression was selectively induced in dead cancer cells after DNA-damaging chemotherapy.
Al-Ejeh
Fares
F
Experimental Therapeutics Laboratory, Hanson Institute, Department of Medical Oncology, Royal Adelaide Hospital, South Australia, Australia.
Darby
Jocelyn M
JM
Brown
Michael P
MP
D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000633:toxicity*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001324:Autoantigens / Q000276:immunology / Q000378:metabolism*; D002843:Chromatin / Q000378:metabolism; D002945:Cisplatin / Q000633:toxicity*; D003432:Cross-Linking Reagents / Q000494:pharmacology; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects*; D004273:DNA, Neoplasm / Q000187:drug effects*; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D019204:GTP-Binding Proteins / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D008214:Lymphocytes / Q000187:drug effects; D009000:Monocytes / Q000187:drug effects; D009336:Necrosis; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D012261:Ribonucleoproteins / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D011503:Transglutaminases / Q000378:metabolism; D014407:Tumor Cells, Cultured; D000097585:SS-B Antigen
D000911:Antibodies, Monoclonal; D000970:Antineoplastic Agents; D001324:Autoantigens; D002843:Chromatin; D002945:Cisplatin; D003432:Cross-Linking Reagents; D004273:DNA, Neoplasm; D019204:GTP-Binding Proteins; D006657:Histones; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D012261:Ribonucleoproteins; D011503:Transglutaminases; D000097585:SS-B Antigen; C468783:H2AX protein, human