{"id":{"repo_id":"columbia-diss","oai_identifier":"oai:academiccommons.columbia.edu:10.7916/D8D79JNQ"},"canonical_url":"https://search.dev.ndltd.org/etd/columbia-diss/oai:academiccommons.columbia.edu:10.7916/D8D79JNQ","repository":{"repo_id":"columbia-diss","name":"Columbia University","base_url":"https://academiccommons.columbia.edu/oai"},"display":{"title":"Studies of SV40-transformation and the Loss of Growth Factor Requirements","abstract":"I found that SV40 transformation induced the loss of several specific growth factor requirements. In particular, SV40 transformed 3T3 fibroblasts had a significantly reduced growth requirement for insulin. A reduced insulin requirement was also observed in several other transformed cell lines. Dose response studies with insulin and insulin-like growth factors indicated that the mitogenic response to insulin is in all probability mediated by IGF-I receptors, and that the reduced insulin requirement observed in transformed fibroblasts actually reflects the loss of a strong IGF-I requirement. IGF-I is under strict pituitary-growth hormone control in vivo, and mediates many if not all of the growth promoting effects of growth hormone. A reduced IGF-I requirement may allow transformed fibroblasts to escape from this major humoral regulatory system. SV40 transformed cells also displayed a significantly diminished requirement for platelet-derived growth factor (PDGF). The loss of this particular growth factor requirement was found to be closely associated with the loss of density-dependent growth inhibition. Cell lines transformed by temperature sensitive mutants of SV40 exhibited a temperature sensitive loss of the PDGF requirement, indicating that SV40 T-antigen mediates this effect. Results pertaining to the temperature sensitivity of the insulin requirement were inconclusive. I found that SV40 could directly reduce the insulin requirement of 3T3 cells in a transformation assay based upon the stringent insulin requirement of 3T3 cells for colony formation. Several such insulin-transformants were isolated and characterized. Although all of these transformants expressed SV40 T-antigen, some of them retained anchorage-dependence and/or a partial PDGF requirement, unlike transformants obtained in the standard density of anchorage assays. A revertant of SV40 transformed 3T3 cells was found to have regained a very strong dependence upon insulin. This dependence was not overcome by re-transformation with Kirsten Murine Sarcoma virus, although retransformation did obviate both its density-dependent growth inhibition and PDGF requirement. Kirsten transformed 3T3 normally display a greatly reduced insulin requirement, indicating that this particular revertant may have suffered a cellular mutation that prevents transforming viruses from induced the reduced insulin requirement.","abstract_html":"I found that SV40 transformation induced the loss of several specific growth factor requirements. In particular, SV40 transformed 3T3 fibroblasts had a significantly reduced growth requirement for insulin. A reduced insulin requirement was also observed in several other transformed cell lines. Dose response studies with insulin and insulin-like growth factors indicated that the mitogenic response to insulin is in all probability mediated by IGF-I receptors, and that the reduced insulin requirement observed in transformed fibroblasts actually reflects the loss of a strong IGF-I requirement. IGF-I is under strict pituitary-growth hormone control in vivo, and mediates many if not all of the growth promoting effects of growth hormone. A reduced IGF-I requirement may allow transformed fibroblasts to escape from this major humoral regulatory system. SV40 transformed cells also displayed a significantly diminished requirement for platelet-derived growth factor (PDGF). The loss of this particular growth factor requirement was found to be closely associated with the loss of density-dependent growth inhibition. Cell lines transformed by temperature sensitive mutants of SV40 exhibited a temperature sensitive loss of the PDGF requirement, indicating that SV40 T-antigen mediates this effect. Results pertaining to the temperature sensitivity of the insulin requirement were inconclusive. I found that SV40 could directly reduce the insulin requirement of 3T3 cells in a transformation assay based upon the stringent insulin requirement of 3T3 cells for colony formation. Several such insulin-transformants were isolated and characterized. Although all of these transformants expressed SV40 T-antigen, some of them retained anchorage-dependence and/or a partial PDGF requirement, unlike transformants obtained in the standard density of anchorage assays. A revertant of SV40 transformed 3T3 cells was found to have regained a very strong dependence upon insulin. This dependence was not overcome by re-transformation with Kirsten Murine Sarcoma virus, although retransformation did obviate both its density-dependent growth inhibition and PDGF requirement. Kirsten transformed 3T3 normally display a greatly reduced insulin requirement, indicating that this particular revertant may have suffered a cellular mutation that prevents transforming viruses from induced the reduced insulin requirement.","abstract_has_math":false,"creators":["Powers, Robert Scott"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2013,"date_issued":"2013","date_published":"2013","updated_at":"2026-07-24T01:44:32Z","subjects":["Biology"],"languages":["English"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://doi.org/10.7916/D8D79JNQ","outbound_label":"DOI","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Powers, Robert Scott"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2013"]},{"key":"dc:type","label":"Dc Type","values":["Theses"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Biology"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["English"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://doi.org/10.7916/D8D79JNQ"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["I found that SV40 transformation induced the loss of several specific growth factor requirements. In particular, SV40 transformed 3T3 fibroblasts had a significantly reduced growth requirement for insulin. A reduced insulin requirement was also observed in several other transformed cell lines. Dose response studies with insulin and insulin-like growth factors indicated that the mitogenic response to insulin is in all probability mediated by IGF-I receptors, and that the reduced insulin requirement observed in transformed fibroblasts actually reflects the loss of a strong IGF-I requirement. IGF-I is under strict pituitary-growth hormone control in vivo, and mediates many if not all of the growth promoting effects of growth hormone. A reduced IGF-I requirement may allow transformed fibroblasts to escape from this major humoral regulatory system. SV40 transformed cells also displayed a significantly diminished requirement for platelet-derived growth factor (PDGF). The loss of this particular growth factor requirement was found to be closely associated with the loss of density-dependent growth inhibition. Cell lines transformed by temperature sensitive mutants of SV40 exhibited a temperature sensitive loss of the PDGF requirement, indicating that SV40 T-antigen mediates this effect. Results pertaining to the temperature sensitivity of the insulin requirement were inconclusive. I found that SV40 could directly reduce the insulin requirement of 3T3 cells in a transformation assay based upon the stringent insulin requirement of 3T3 cells for colony formation. Several such insulin-transformants were isolated and characterized. Although all of these transformants expressed SV40 T-antigen, some of them retained anchorage-dependence and/or a partial PDGF requirement, unlike transformants obtained in the standard density of anchorage assays. A revertant of SV40 transformed 3T3 cells was found to have regained a very strong dependence upon insulin. This dependence was not overcome by re-transformation with Kirsten Murine Sarcoma virus, although retransformation did obviate both its density-dependent growth inhibition and PDGF requirement. Kirsten transformed 3T3 normally display a greatly reduced insulin requirement, indicating that this particular revertant may have suffered a cellular mutation that prevents transforming viruses from induced the reduced insulin requirement."]},{"key":"dc:title","label":"Title","values":["Studies of SV40-transformation and the Loss of Growth Factor Requirements"]}]}],"canonical_facts":{"dc:creator":["Powers, Robert Scott"],"dc:date":["2013"],"dc:description":["I found that SV40 transformation induced the loss of several specific growth factor requirements. In particular, SV40 transformed 3T3 fibroblasts had a significantly reduced growth requirement for insulin. A reduced insulin requirement was also observed in several other transformed cell lines. Dose response studies with insulin and insulin-like growth factors indicated that the mitogenic response to insulin is in all probability mediated by IGF-I receptors, and that the reduced insulin requirement observed in transformed fibroblasts actually reflects the loss of a strong IGF-I requirement. IGF-I is under strict pituitary-growth hormone control in vivo, and mediates many if not all of the growth promoting effects of growth hormone. A reduced IGF-I requirement may allow transformed fibroblasts to escape from this major humoral regulatory system. SV40 transformed cells also displayed a significantly diminished requirement for platelet-derived growth factor (PDGF). The loss of this particular growth factor requirement was found to be closely associated with the loss of density-dependent growth inhibition. Cell lines transformed by temperature sensitive mutants of SV40 exhibited a temperature sensitive loss of the PDGF requirement, indicating that SV40 T-antigen mediates this effect. Results pertaining to the temperature sensitivity of the insulin requirement were inconclusive. I found that SV40 could directly reduce the insulin requirement of 3T3 cells in a transformation assay based upon the stringent insulin requirement of 3T3 cells for colony formation. Several such insulin-transformants were isolated and characterized. Although all of these transformants expressed SV40 T-antigen, some of them retained anchorage-dependence and/or a partial PDGF requirement, unlike transformants obtained in the standard density of anchorage assays. A revertant of SV40 transformed 3T3 cells was found to have regained a very strong dependence upon insulin. This dependence was not overcome by re-transformation with Kirsten Murine Sarcoma virus, although retransformation did obviate both its density-dependent growth inhibition and PDGF requirement. Kirsten transformed 3T3 normally display a greatly reduced insulin requirement, indicating that this particular revertant may have suffered a cellular mutation that prevents transforming viruses from induced the reduced insulin requirement."],"dc:identifier":["https://doi.org/10.7916/D8D79JNQ"],"dc:language":["English"],"dc:subject":["Biology"],"dc:title":["Studies of SV40-transformation and the Loss of Growth Factor Requirements"],"dc:type":["Theses"]},"updated_at":"2026-07-24T01:44:32Z"}