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Mechanisms and regulation of gene amplification
148
29
Abstracts GENETIC CHANGES IN BONE AND SOFT TISSUE TUMORS Nils Mandahl Department of Clinical Genetics, University Hospital, Lund, Sweden
The findings of clonal chromosome aberrations in more than 500, 180 of which are new, unpublished cases, benign and malignant bone and soft tissue tumors are summarized. Only iipomas and Ewings's sarcomas have been studied in numbers above 100. Several characteristic aberrations have been identified. These include t(X;18) in synovial sarcoma (> 90%), t(12;16) in myxoid liposarcoma (90%), t(11;22) in Ewing's sarcoma (80%), t(2;13) in alveolar rhabdomyosarcoma (70%), and in smaller series t(12;22) in clear cell sarcoma of tendons and aponeuroses, and t(9;22) in extraskeletal myxoid chondrosarcoma. Supernumerary ring chromosomes in near-rill? Ioid karyotypes .seem to characterize.. a group, of borderhne and Iow-mahgnant tumors, including atypical lipoma/weil differentiated iiposarcoma, dermatofibrosarcoma protuberans, parosteal osteosarcoma, and malignant fibrous histiocytoma. Benign Sehwannomas have -22, and chondromas and a subgroup of hemangiopericytomas have 12ql3-15aberrations. Different cytogenetic subgroups are found among lipomas; one is characterized by t(3;12) or other aberrations involving 12q13-15. The most common numerical changes, found in several tumor types, are -13, +7, +8, and +20.
"ROGUE" LYMPHOCYTES: PASSING CURIOSITY OR BASIC PROCESS? James V. Neel, University of Michigan Medical School, Medical Science i[ M4708, Ann Arbor, MI 48109-0618. The typical "rogue" cell is a highly abnormal cultured lymphocyte which at the time of first cell division in culture exhibits -3-4 dicentric and 1 tricentric chromosome plus 6-8 "double minutes". Such cells have now been observed in Amerindians, Japanese, Englishmen, and Ukrainians. They occur in specific individuals in geographically localized bursts; at the height of a burst, 1 in 200 lymphocytes in an individual exhibiting the phenomenon may be abnormal. Thus far there is no age-sex predilection nor, in the studies on Japanese, was there variation by year over a 15-year period. Most of these ceils would self-destruct in a mitotic division. Whether the phenomenon occurs in other cell types is unknown. The speculation is advanced that the phenomenon occurs in both somatic and germinal tissue, and that the least damaged among these cells - - -1 in 1000 ~ can divide, establishing a clone which may play a role in oncugenesis, teratogenesis, and mutation. It is suggested the phenomenon results from the periodic activation of latent retroposons. Thus far the cells have been observed as an incidental finding in otber-directed investigations. A purpose of this presentation is to elicit discussion concerning more efficient ways to investigate the frequency and epidemiology of the phenomenon, and to test the hypothesis of a retroposon etiology. 30
Molecular genetic investigations have recently shown that CHOP. a member of the C / E B P gene family localized to 12q13, is rearranged in myxoid iiposarcoma resulting in a fusion gene and hybrid mRNA. CHOP is not rearranged in other tumors with 12q13-15 aberrations, indicating that the breakpoints are different in these tumors.
31
MECHANISMS AND REGULATION OF GENE AMPLIFICATION
George IL Stark, Ph.D., The Cleveland Clinic Foundation, Cleveland, Ohio Recent studies emphasizing fluon~scence in s/tu hybridization have revealed that fusion of sister chromatids at or near one pair of tclomeres is a frequent initiating event of amplification. The resulting dicentric chromatid onde~oes bridge-breakage-fusion cycles in successive cell divisions, leading to unequal distribution into daughter cells of DNA sequences lying betweea the two centrongre& The ssme basic process therefore leads both to increases (amplification) aad to decreases (loss of hetemzygosity) of genetic material. The broken chromosome ends generated in each cycle are likely to be a rcgulalory signal recognized in normal cells (not permissive for empfification) through a system involving p53. resultin~ in cell cycle ar/e.st or cell death, lack of this system in pcmussive cells allows cells with damaged DNA to survive and propagate, generating genetic diversity in the growing population. This situation is of obvious impe/'tance in understanding how tumors are formed and progress.
AMPLIFICATION OF THE G E / ~ FOR A NOVEL MULTIDRUG RESISTANCE ASSOCIATED PROTEIN (MRP) IN NON-P-GLYCOPROTEIN MI~IATI~D DOXORUBICIN-SPJ~-rmJ SOLID TUMOR CELLS L I N ~ . M.L. Slovak, J. Ho, E.U. Kurz, R.G. DeWey and S.P.C. Cole, City of Hope National Medical C a s ~ , Duarte, CA and Canc~ Resem,ch ~ e s , Queen's Univemty, Kingston, Ontario, Canada Resistance to anticanca agents is a major limiting factor in curative cancer therapy. R__~e~___dy,a m u ] l ~ resimn~ zmoa~xl pn~/n 0d[RP) thaxbeionSsto the ATPbinding casse~ lrmzpm~r Ipmefamily has bern imla~l from the doxorubicin (DOX)-selzcted small cell lut~ canc~ cell line, H69AR. This cell line displays muifidnsg resistmwc (MDR) but does not ovetzgptws P-glyvt~-6~eia. The 6.5 kb mRNA of MRP is I00 to 200-fold oVa~lW~md in Hf~AR cells but not in the drug semifive gevertant celt line, H69PR.
32
soutben~ btom~ ~ ~ m~or ~ ~ of M ] ~ is Sue m~fica~m. Ch~z~owm~ in situ hybridim~m maps the ~ coding f ~ MRP to chromomme band l~p13.1 ~ , Dec. 1992). We have now de,mzia~ mazZ a P am.NA is m o ~ -tS-
fo~ m ~ D O X ~ ~ ~ m'zeZefl~4 ce~ line. u s ~ ac~ammm z 6 - ~ ~ c ~ m m o m z6 num~izd was loadized to two HSlbl~ari~ nual~ cluutummm~ in ]FI69AR and to multiple dledvadve chrommom~ m m'1N0/DR4 including the ~ ' ~ t ~ 1 5 ) .
m v o ~ in the ~ cell lines. ( S ~ e d
of MDR in ~
wlld~
by MI~C Canada and NCl CA-33572)
29
Abstracts GENETIC CHANGES IN BONE AND SOFT TISSUE TUMORS Nils Mandahl Department of Clinical Genetics, University Hospital, Lund, Sweden
The findings of clonal chromosome aberrations in more than 500, 180 of which are new, unpublished cases, benign and malignant bone and soft tissue tumors are summarized. Only iipomas and Ewings's sarcomas have been studied in numbers above 100. Several characteristic aberrations have been identified. These include t(X;18) in synovial sarcoma (> 90%), t(12;16) in myxoid liposarcoma (90%), t(11;22) in Ewing's sarcoma (80%), t(2;13) in alveolar rhabdomyosarcoma (70%), and in smaller series t(12;22) in clear cell sarcoma of tendons and aponeuroses, and t(9;22) in extraskeletal myxoid chondrosarcoma. Supernumerary ring chromosomes in near-rill? Ioid karyotypes .seem to characterize.. a group, of borderhne and Iow-mahgnant tumors, including atypical lipoma/weil differentiated iiposarcoma, dermatofibrosarcoma protuberans, parosteal osteosarcoma, and malignant fibrous histiocytoma. Benign Sehwannomas have -22, and chondromas and a subgroup of hemangiopericytomas have 12ql3-15aberrations. Different cytogenetic subgroups are found among lipomas; one is characterized by t(3;12) or other aberrations involving 12q13-15. The most common numerical changes, found in several tumor types, are -13, +7, +8, and +20.
"ROGUE" LYMPHOCYTES: PASSING CURIOSITY OR BASIC PROCESS? James V. Neel, University of Michigan Medical School, Medical Science i[ M4708, Ann Arbor, MI 48109-0618. The typical "rogue" cell is a highly abnormal cultured lymphocyte which at the time of first cell division in culture exhibits -3-4 dicentric and 1 tricentric chromosome plus 6-8 "double minutes". Such cells have now been observed in Amerindians, Japanese, Englishmen, and Ukrainians. They occur in specific individuals in geographically localized bursts; at the height of a burst, 1 in 200 lymphocytes in an individual exhibiting the phenomenon may be abnormal. Thus far there is no age-sex predilection nor, in the studies on Japanese, was there variation by year over a 15-year period. Most of these ceils would self-destruct in a mitotic division. Whether the phenomenon occurs in other cell types is unknown. The speculation is advanced that the phenomenon occurs in both somatic and germinal tissue, and that the least damaged among these cells - - -1 in 1000 ~ can divide, establishing a clone which may play a role in oncugenesis, teratogenesis, and mutation. It is suggested the phenomenon results from the periodic activation of latent retroposons. Thus far the cells have been observed as an incidental finding in otber-directed investigations. A purpose of this presentation is to elicit discussion concerning more efficient ways to investigate the frequency and epidemiology of the phenomenon, and to test the hypothesis of a retroposon etiology. 30
Molecular genetic investigations have recently shown that CHOP. a member of the C / E B P gene family localized to 12q13, is rearranged in myxoid iiposarcoma resulting in a fusion gene and hybrid mRNA. CHOP is not rearranged in other tumors with 12q13-15 aberrations, indicating that the breakpoints are different in these tumors.
31
MECHANISMS AND REGULATION OF GENE AMPLIFICATION
George IL Stark, Ph.D., The Cleveland Clinic Foundation, Cleveland, Ohio Recent studies emphasizing fluon~scence in s/tu hybridization have revealed that fusion of sister chromatids at or near one pair of tclomeres is a frequent initiating event of amplification. The resulting dicentric chromatid onde~oes bridge-breakage-fusion cycles in successive cell divisions, leading to unequal distribution into daughter cells of DNA sequences lying betweea the two centrongre& The ssme basic process therefore leads both to increases (amplification) aad to decreases (loss of hetemzygosity) of genetic material. The broken chromosome ends generated in each cycle are likely to be a rcgulalory signal recognized in normal cells (not permissive for empfification) through a system involving p53. resultin~ in cell cycle ar/e.st or cell death, lack of this system in pcmussive cells allows cells with damaged DNA to survive and propagate, generating genetic diversity in the growing population. This situation is of obvious impe/'tance in understanding how tumors are formed and progress.
AMPLIFICATION OF THE G E / ~ FOR A NOVEL MULTIDRUG RESISTANCE ASSOCIATED PROTEIN (MRP) IN NON-P-GLYCOPROTEIN MI~IATI~D DOXORUBICIN-SPJ~-rmJ SOLID TUMOR CELLS L I N ~ . M.L. Slovak, J. Ho, E.U. Kurz, R.G. DeWey and S.P.C. Cole, City of Hope National Medical C a s ~ , Duarte, CA and Canc~ Resem,ch ~ e s , Queen's Univemty, Kingston, Ontario, Canada Resistance to anticanca agents is a major limiting factor in curative cancer therapy. R__~e~___dy,a m u ] l ~ resimn~ zmoa~xl pn~/n 0d[RP) thaxbeionSsto the ATPbinding casse~ lrmzpm~r Ipmefamily has bern imla~l from the doxorubicin (DOX)-selzcted small cell lut~ canc~ cell line, H69AR. This cell line displays muifidnsg resistmwc (MDR) but does not ovetzgptws P-glyvt~-6~eia. The 6.5 kb mRNA of MRP is I00 to 200-fold oVa~lW~md in Hf~AR cells but not in the drug semifive gevertant celt line, H69PR.
32
soutben~ btom~ ~ ~ m~or ~ ~ of M ] ~ is Sue m~fica~m. Ch~z~owm~ in situ hybridim~m maps the ~ coding f ~ MRP to chromomme band l~p13.1 ~ , Dec. 1992). We have now de,mzia~ mazZ a P am.NA is m o ~ -tS-
fo~ m ~ D O X ~ ~ ~ m'zeZefl~4 ce~ line. u s ~ ac~ammm z 6 - ~ ~ c ~ m m o m z6 num~izd was loadized to two HSlbl~ari~ nual~ cluutummm~ in ]FI69AR and to multiple dledvadve chrommom~ m m'1N0/DR4 including the ~ ' ~ t ~ 1 5 ) .
m v o ~ in the ~ cell lines. ( S ~ e d
of MDR in ~
wlld~
by MI~C Canada and NCl CA-33572)