{"id":"e1e5768f-fc76-55e7-b08b-9babd9c022bd","stable_key":"ea2f0904-ab2c-5d1e-a3d4-3f7ecdd70cd6:caf-checkpoint","predicate":"disrupts","statement":"Caffeine-treated irradiated A549 cells failed G2 arrest and showed radioresistant DNA synthesis after S-phase irradiation.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"b064a463-846b-5d6c-aa28-bea0ae0f7b22","mechanism_event_label":"The cancer-cell experiment measured altered checkpoint behavior.","subject":{"id":"ef028472-7c33-583d-b52e-40676004d370","slug":"caffeine","display_name":"Caffeine","entity_type_key":"small_molecule"},"object":{"id":"ec06dc4c-c123-5695-9727-002bba6bdf1f","slug":"dna-damage-checkpoint-arrest","display_name":"DNA-damage-induced cell-cycle checkpoint arrest","entity_type_key":"cellular_process"},"evidence_count":1,"mechanism_event":{"id":"b064a463-846b-5d6c-aa28-bea0ae0f7b22","stable_key":"ea2f0904-ab2c-5d1e-a3d4-3f7ecdd70cd6:caf-checkpoint-event","event_type":"observed_relationship","label":"The cancer-cell experiment measured altered checkpoint behavior.","description":"Caffeine-treated irradiated A549 cells failed G2 arrest and showed radioresistant DNA synthesis after S-phase irradiation.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"ef028472-7c33-583d-b52e-40676004d370","slug":"caffeine","display_name":"Caffeine","entity_type_key":"small_molecule"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"ec06dc4c-c123-5695-9727-002bba6bdf1f","slug":"dna-damage-checkpoint-arrest","display_name":"DNA-damage-induced cell-cycle checkpoint arrest","entity_type_key":"cellular_process"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"243ad948-2281-53f8-8e53-32247253668d","slug":"atm","display_name":"Human ATM kinase","entity_type_key":"protein"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"fe8d147a-fd3c-5768-ae24-f6c4fbd2ae8d","slug":"atr","display_name":"Human ATR kinase","entity_type_key":"protein"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""}]},"contexts":[{"dimension":"evidence_access","value_text":"Primary abstract","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Irradiated cultured A549 lung carcinoma cells.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"These findings are not a demonstrated clinical caffeine–radiotherapy benefit.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Caffeine collection; salts, coffee, species and coexposure contexts retain their identities.","comparator":null,"unit":null,"notes":"","entity":{"slug":"caffeine","display_name":"Caffeine","entity_type_key":"small_molecule"}},{"dimension":"plain_language","value_text":"The cancer-cell experiment measured altered checkpoint behavior.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Inhibition of ATM and ATR kinase activities by the radiosensitizing agent, caffeine. · 1999 · https://pubmed.ncbi.nlm.nih.gov/10485486/","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"f053b939-bb1b-5a82-9c0a-89e85990e8ae","evidence_kind":"source_excerpt","locator":"Lines 428-434","start_line":428,"end_line":434,"excerpt":"## caf-checkpoint\nThe cancer-cell experiment measured altered checkpoint behavior.\nCaffeine-treated irradiated A549 cells failed G2 arrest and showed radioresistant DNA synthesis after S-phase irradiation.\nModel: Irradiated cultured A549 lung carcinoma cells.\nLimitations: These findings are not a demonstrated clinical caffeine–radiotherapy benefit.\nEvidence access: Primary abstract\nInhibition of ATM and ATR kinase activities by the radiosensitizing agent, caffeine. · 1999 · https://pubmed.ncbi.nlm.nih.gov/10485486/","model_system":"Irradiated cultured A549 lung carcinoma cells.","directness":"reported_statement","verification_status":"source_derived_draft","notes":"Original curation paraphrase; evidence access stated with the claim.","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"40a654db-878c-5471-bc6c-88f4f52599c0","stable_key":"import-ea2f0904-ab2c-5d1e-a3d4-3f7ecdd70cd6","title":"Caffeine: receptors, metabolism, nutrient interactions, adaptation and discovery questions (2026-09-18)","document_type":"imported_text","citation_label":"AI-assisted research curation; primary-abstract references and experimental limitations individually identified. 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