{"id":23046,"date":"2015-03-01T16:20:29","date_gmt":"2015-03-01T14:20:29","guid":{"rendered":"https:\/\/bilimvegelecek.com.tr\/?p=23046"},"modified":"2018-04-13T16:31:33","modified_gmt":"2018-04-13T13:31:33","slug":"genler-kanser-ve-sans","status":"publish","type":"post","link":"https:\/\/bilimvegelecek.com.tr\/index.php\/2015\/03\/01\/genler-kanser-ve-sans","title":{"rendered":"Genler, kanser ve \u015fans"},"content":{"rendered":"

Ortal\u0131\u011f\u0131 kar\u0131\u015ft\u0131ran makale 2 Ocak tarihli Science dergisinde yer ald\u0131. \u00c7al\u0131\u015fma, kanser tiplerinin g\u00f6r\u00fclme s\u0131kl\u0131\u011f\u0131 aras\u0131ndaki farkl\u0131l\u0131\u011f\u0131n \u201c\u015fanss\u0131zl\u0131\u011fa\u201d ba\u011fl\u0131 olabilece\u011fini iddia ediyordu. Nas\u0131l olur da rasgele mutasyonun yol a\u00e7t\u0131\u011f\u0131 \u201c\u015fanss\u0131zl\u0131k\u201d, ki\u015finin geneti\u011fi, ya\u015fam tarz\u0131, \u00e7evresel fakt\u00f6rler ile k\u0131yaslanabilirdi? <\/em><\/p>\n

Bu y\u0131l\u0131n ba\u015f\u0131nda Science<\/em> dergisinde yay\u0131mlanan bir makale, kanser konusunda var olan bilgilerimizde sars\u0131c\u0131 bir etki yapt\u0131. \u00c7\u00fcnk\u00fc bu \u00e7al\u0131\u015fma, kanser tiplerinin g\u00f6r\u00fclme s\u0131kl\u0131\u011f\u0131 aras\u0131ndaki farkl\u0131l\u0131\u011f\u0131n \u201c\u015fanss\u0131zl\u0131\u011fa\u201d ba\u011fl\u0131 olabilece\u011fini iddia ediyordu. Makalenin yay\u0131mlanmas\u0131n\u0131 ani bir itiraz ve protesto f\u0131rt\u0131nas\u0131 takip etti. Nas\u0131l olur da rasgele mutasyonun yol a\u00e7t\u0131\u011f\u0131 \u201c\u015fanss\u0131zl\u0131k\u201d, ki\u015finin geneti\u011fi (ailenin su\u00e7u), ya\u015fam tarz\u0131 (ki\u015finin su\u00e7u), \u00e7evresel fakt\u00f6rler (ba\u015fkas\u0131n\u0131n su\u00e7u) ile k\u0131yaslanabilirdi? Bu, topluma tamamen yanl\u0131\u015f mesaj g\u00f6nderebilecek bir \u00e7al\u0131\u015fma ve yay\u0131nd\u0131. Acaba ger\u00e7ekten \u00f6yle mi? Neticede elimizde epeyce okunacak bilimsel materyal ve neredeyse 21. y\u00fczy\u0131l\u0131n tamam\u0131nda bizleri me\u015fgul edecek \u00f6nemde sorular kald\u0131.<\/p>\n

Ortal\u0131\u011f\u0131 kar\u0131\u015ft\u0131ran makale 2 Ocak tarihinde yay\u0131mlanan Science<\/em> dergisinde yer ald\u0131. (http:\/\/www.sciencemag.org\/content\/347\/6217\/78.abstract)<\/p>\n

Dr. Bert Vogelstein ve Dr. Cristian Tomasetti\u2019ye (Johns Hopkins \u00dcniversitesi T\u0131p Fak\u00fcltesi) g\u00f6re kanserin baz\u0131 organlarda di\u011ferlerine g\u00f6re kat be kat fazla g\u00f6r\u00fclmesinin nedeni k\u00f6k h\u00fccre b\u00f6l\u00fcnme say\u0131s\u0131yla a\u00e7\u0131klanabilecekti. Normal k\u00f6k h\u00fccrelerde DNA replikasyonu s\u0131ras\u0131nda olu\u015fan herhangi bir hata sonucu meydana gelen mutasyonlar, kanser geli\u015fimiyle direkt ili\u015fkiliydi. Bu da \u201c\u015fanss\u0131zl\u0131\u011f\u0131n\u201d, \u00e7evresel ve ailesel fakt\u00f6rlerden daha etkin olabilece\u011fini g\u00f6stermekteydi.<\/p>\n

\u00c7e\u015fitli organlarda kanser g\u00f6r\u00fclme s\u0131kl\u0131\u011f\u0131ndaki a\u015f\u0131r\u0131 de\u011fi\u015fkenlikler \u00e7oktand\u0131r biliniyordu. \u00d6rne\u011fin bu oran akci\u011fer kanseri i\u00e7in y\u00fczde 6,9 iken, tiroitte y\u00fczde 1,08, beyinde y\u00fczde 0,6 oran\u0131ndad\u0131r. Baz\u0131 farkl\u0131l\u0131klar belirgin risk fakt\u00f6rleriyle ba\u011flant\u0131l\u0131d\u0131r. Sigara, alkol, ultraviyole \u0131\u015f\u0131n\u0131na maruz kalma veya HPV (human papilloma vir\u00fcs) gibi. Ancak bunun d\u0131\u015f\u0131nda pek \u00e7ok durumda nedenler anla\u015f\u0131lmazd\u0131r. \u00d6rne\u011fin ince ba\u011f\u0131rsa\u011f\u0131m\u0131z, kan-beyin engeliyle korunan beynimize nazaran risklere \u00e7ok daha a\u00e7\u0131k bir v\u00fccut par\u00e7am\u0131zken; ince barsak kanserleri, beyin kanserlerinden 3 kat az g\u00f6r\u00fclmektedir.<\/p>\n

E\u011fer genetik ve \u00e7evresel fakt\u00f6rler t\u00fcm farkl\u0131 oranlar\u0131 a\u00e7\u0131klayam\u0131yorsa ba\u015fka nas\u0131l bir a\u00e7\u0131klama d\u00fc\u015f\u00fcn\u00fclmelidir? Buradaki \u00fc\u00e7\u00fcnc\u00fc fakt\u00f6r, her bir dokudaki k\u00f6k h\u00fccrelerin ya\u015fam boyu b\u00f6l\u00fcnme say\u0131lar\u0131n\u0131n rasgele bir etkiyle DNA replikasyonu s\u0131ras\u0131nda mutasyonlar olu\u015fturmas\u0131d\u0131r. Dahas\u0131 bu rasgele etki, kanser geli\u015fimine genetik ve \u00e7evresel etkenlerden \u00e7ok daha fazla neden olabilmektedir.<\/p>\n

G\u00fcncel \u00e7al\u0131\u015fmalar, pek \u00e7ok genomik de\u011fi\u015fikli\u011fin, karsinojenik fakt\u00f6rlerden \u00e7ok DNA replikasyonu s\u0131ras\u0131ndaki \u015fansa ba\u011fl\u0131 oldu\u011funu g\u00f6stermektedir. T\u00fcm insan h\u00fccre tiplerinin endojen mutasyon oranlar\u0131n\u0131n hemen hemen ayn\u0131 oldu\u011funun belirlenmesi, her bir organdaki k\u00f6k h\u00fccre b\u00f6l\u00fcnme say\u0131s\u0131yla o organda kanser geli\u015fme riski aras\u0131nda niceliksel bir ba\u011flant\u0131 olabilece\u011fini g\u00f6stermi\u015ftir.<\/p>\n

Dokulardaki pek \u00e7ok h\u00fccre k\u0131smen ya da tamamen farkl\u0131la\u015fm\u0131\u015f oldu\u011fundan ya\u015fam s\u00fcreleri k\u0131sad\u0131r ve bir t\u00fcm\u00f6r olu\u015fturabilecek durumda de\u011fildirler. Sadece k\u00f6k h\u00fccreler kendilerini yenileyebildiklerinden dokunun ana mimarisini olu\u015fturacak kapasitededirler. K\u00f6k h\u00fccreler doku i\u00e7inde s\u0131kl\u0131kla di\u011fer h\u00fccrelere nazaran daha az bir oranda bulunurlar ve yak\u0131n zamana kadar do\u011falar\u0131, say\u0131lar\u0131, hiyerar\u015fik b\u00f6l\u00fcnme modelleriyle ilgili bilgimiz yoktu.<\/p>\n

Vogelstein ve Tomasetti, 31 doku \u00f6rne\u011finde k\u00f6k h\u00fccre b\u00f6l\u00fcnmelerinin k\u00fcm\u00fclatif toplam\u0131n\u0131 elde etmeye \u00e7al\u0131\u015ft\u0131lar. Ve bu say\u0131lar\u0131, Amerikan halk\u0131 aras\u0131nda ayn\u0131 dokularda g\u00f6r\u00fclen ya\u015fam boyu kanser riskiyle kar\u015f\u0131la\u015ft\u0131rd\u0131lar. (Bkz. Grafik)<\/p>\n

Ba\u011f\u0131ms\u0131z de\u011fi\u015fkenler aras\u0131ndaki ili\u015fkiyi g\u00f6steren grafikte, k\u00f6k h\u00fccre b\u00f6l\u00fcnme say\u0131s\u0131 ile kanser riski aras\u0131nda ki ili\u015fki 0,804 olarak hesaplanm\u0131\u015ft\u0131r ki matematiksel olarak ortaya \u00e7\u0131kan rakam 1\u2019e ne kadar yak\u0131nsa bu ili\u015fki o kadar g\u00fc\u00e7l\u00fc demektir.<\/p>\n

Ara\u015ft\u0131rmac\u0131lar\u0131n ikinci ad\u0131m\u0131 ise, rasgelenin etkisinin di\u011fer risk fakt\u00f6rlerine g\u00f6re farkl\u0131 olup olmad\u0131\u011f\u0131n\u0131n say\u0131sal belirlenmesi idi. 22 kanser t\u00fcr\u00fcn\u00fcn b\u00fcy\u00fck \u00f6l\u00e7\u00fcde k\u00f6k h\u00fccre b\u00f6l\u00fcnmesi s\u0131ras\u0131nda ortaya \u00e7\u0131kan rasgele DNA mutasyonlar\u0131na ba\u011fl\u0131 \u201c\u015fanss\u0131zl\u0131k\u201d fakt\u00f6r\u00fc ile a\u00e7\u0131klanabilece\u011fini; 9 kanser t\u00fcr\u00fcn\u00fcn ise \u201c\u015fanss\u0131zl\u0131k\u201dla a\u00e7\u0131klanandan \u00e7ok daha y\u00fcksek insidansta oldu\u011funu ve burada da \u201c\u015fanss\u0131zl\u0131k, kal\u0131t\u0131m ve \u00e7evresel fakt\u00f6r\u201dlerin bir arada bulunmas\u0131na ba\u011fl\u0131 bir durum olabilece\u011fi g\u00f6sterildi.<\/p>\n

Vogelstein, \u00e7al\u0131\u015fmalar\u0131n\u0131n bir doku tipindeki k\u00f6k h\u00fccre b\u00f6l\u00fcnme say\u0131s\u0131ndaki de\u011fi\u015fmenin, ayn\u0131 dokudaki kanser g\u00f6r\u00fclme oran\u0131ndaki de\u011fi\u015fim ile ba\u011flant\u0131l\u0131 oldu\u011funu g\u00f6sterdi\u011fini belirtiyor. \u00d6rne\u011fin kal\u0131n barsak k\u00f6k h\u00fccre b\u00f6l\u00fcnme say\u0131s\u0131 fazlal\u0131\u011f\u0131 bunun az oldu\u011fu ince ba\u011f\u0131rsa\u011fa g\u00f6re kanser g\u00f6r\u00fclme s\u0131kl\u0131\u011f\u0131n\u0131 da art\u0131rmaktad\u0131r. Farelerde yap\u0131lan deneylerde ise kal\u0131n barsak k\u00f6k h\u00fccre b\u00f6l\u00fcnmesinin az oldu\u011fu, bu canl\u0131larda da b\u00f6l\u00fcnmenin fazla g\u00f6zlendi\u011fi ince ba\u011f\u0131rsak kanserlerinin daha fazla g\u00f6r\u00fcld\u00fc\u011f\u00fc izlenmi\u015ftir.<\/p>\n

Elde edilen sonu\u00e7lar\u0131n en \u00f6nemli katk\u0131s\u0131 toplum sa\u011fl\u0131\u011f\u0131 konusunda olacakt\u0131r hi\u00e7 ku\u015fkusuz. Hangi tip mekanizman\u0131n kanser olu\u015fumunda daha bask\u0131n oldu\u011fu bilinirse birincil ve ikincil korumalar yap\u0131labilir ve hatta tedavi konusunda gereksiz vakit kay\u0131plar\u0131ndan ziyade hedefe do\u011fru kesin ad\u0131mlar at\u0131labilir.<\/p>\n

Makalenin yay\u0131mlanmas\u0131 ve \u00e7e\u015fitli dergilerde \u00e7al\u0131\u015fmayla ilgili yap\u0131lan yorumlar, at\u0131lan ba\u015fl\u0131klar ortal\u0131\u011f\u0131 epeyce kar\u0131\u015ft\u0131rd\u0131. (http:\/\/www.theguardian.com\/science\/grrlscientist\/2015\/jan\/02\/bad-luck-bad-journalism-and-cancer-rates). Bir bilimsel ara\u015ft\u0131rman\u0131n pop\u00fcler yaz\u0131nda nas\u0131l yer almas\u0131 gerekti\u011finden t\u0131p biliminde matemati\u011fin rol\u00fcne kadar pek \u00e7ok tart\u0131\u015fma dergi makalelerinde yerini ald\u0131.<\/p>\n

(http:\/\/news.sciencemag.org\/biology\/2015\/01\/bad-luck-and-cancer-science-reporter-s-reflections-controversial-story) (http:\/\/news.sciencemag.org\/biology\/2015\/01\/simple-math-explains-why-you-may-or-may-not-get-cancer).<\/p>\n

Bu arada en keskin \u00e7\u0131k\u0131\u015f 13 Ocak g\u00fcn\u00fc yay\u0131mlad\u0131\u011f\u0131 bas\u0131n b\u00fclteniyle WHO\u2019nun kanser ara\u015ft\u0131rmalar\u0131 ajans\u0131ndan geldi: http:\/\/www.iarc.fr\/en\/media-centre\/pr\/2015\/pdfs\/<\/p>\n

A\u00e7\u0131klamada, \u00e7al\u0131\u015fmada elde edilen sonu\u00e7larla ayn\u0131 fikirde olmad\u0131klar\u0131 belirtiliyordu. Makale yanl\u0131\u015f yorumlan\u0131rsa hem s\u00fcrmekte olan kanser ara\u015ft\u0131rmalar\u0131 hem de halk sa\u011fl\u0131\u011f\u0131 a\u00e7\u0131s\u0131ndan olumsuzluklar yaratabilecektir. Mevcut durumda toplumda g\u00f6r\u00fclen kanserlerin yar\u0131s\u0131 kadar\u0131 \u00f6nlenebilmektedir. \u201c\u015eanss\u0131zl\u0131\u011f\u0131n\u201d en belirgin fakt\u00f6r oldu\u011funu s\u00f6ylemek yanl\u0131\u015f okundu\u011funda, hastal\u0131\u011f\u0131n nedenlerini belirleme ve olu\u015fumunu engelleme \u00e7abalar\u0131n\u0131 sekteye u\u011fratabilecek ve toplumsal olarak da yanl\u0131\u015f bir alg\u0131 yaratabilecektir.<\/p>\n

\"\"
Grafik: X-ekseni (yatay eksen), k\u00f6k h\u00fccre b\u00f6l\u00fcnme say\u0131s\u0131n\u0131; y-ekseni (dikey eksen), ya\u015fam boyu g\u00f6r\u00fclebilecek kanser riski oranlar\u0131n\u0131 g\u00f6steriyor. Grafikte, toplumda g\u00f6r\u00fclebilecek kanser tipleri ve bunlar\u0131n g\u00f6r\u00fclme riskiyle k\u00f6k h\u00fccre b\u00f6l\u00fcnme say\u0131lar\u0131n\u0131n do\u011fru orant\u0131l\u0131 oldu\u011fu belirtilmi\u015ftir.<\/figcaption><\/figure>\n

Ge\u00e7ti\u011fimiz 50 y\u0131ll\u0131k s\u00fcre\u00e7te epidemiyolojik ara\u015ft\u0131rmalar pek \u00e7ok kanser t\u00fcr\u00fcn\u00fcn baz\u0131 toplumlarda s\u0131k\u00e7a g\u00f6r\u00fcl\u00fcrken baz\u0131lar\u0131nda neredeyse hi\u00e7 olmad\u0131\u011f\u0131n\u0131 ve bu \u00f6zelliklerin de zaman i\u00e7inde de\u011fi\u015fikli\u011fe u\u011frayabildi\u011fini g\u00f6stermi\u015ftir. \u00d6rne\u011fin yemek borusu kanseri Do\u011fu Afrika\u2019da yayg\u0131nken Bat\u0131 Afrika\u2019da epey nadirdir. Japonya\u2019da bir zamanlar ender rastlanan kolorektal kanserler son 20 y\u0131lda 4 kat art\u0131\u015f g\u00f6stermi\u015ftir. Bu veriler, \u00e7evresel etkenler ve ki\u015fisel ya\u015fam tarz\u0131 de\u011fi\u015fikliklerinin \u00f6nemini a\u00e7\u0131\u011fa \u00e7\u0131karmaktad\u0131r.<\/p>\n

Tomasetti-Vogelstein makalesine kar\u015f\u0131 \u00e7\u0131k\u0131lan bir nokta da, toplumda ender g\u00f6r\u00fclen kanser oranlar\u0131yla \u00e7al\u0131\u015f\u0131lm\u0131\u015f olmas\u0131d\u0131r. Osteosarkom, medullablastom gibi tipler total kanser y\u00fck\u00fcn\u00fcn k\u00fc\u00e7\u00fck bir k\u0131sm\u0131n\u0131 olu\u015fturmaktad\u0131r. \u00c7al\u0131\u015fma ayn\u0131 zamanda toplumlar aras\u0131nda ve zamanla de\u011fi\u015fiklik g\u00f6steren yayg\u0131n kanser tiplerini de veri yoklu\u011fu y\u00fcz\u00fcnden d\u0131\u015far\u0131da b\u0131rakm\u0131\u015ft\u0131r. Dahas\u0131 kar\u015f\u0131la\u015ft\u0131rmalar sadece Amerika\u2019da g\u00f6r\u00fclen kanserlerle ilgili yap\u0131lm\u0131\u015ft\u0131r. Oysa farkl\u0131 toplumlarda farkl\u0131 nedenler \u00f6n planda olabilir.<\/p>\n

H\u00fccre b\u00f6l\u00fcnme say\u0131s\u0131n\u0131n artmas\u0131 elbette mutasyon riskini art\u0131r\u0131p kanser olu\u015fumunda etkili olacakt\u0131r. Ancak \u00e7evre fakt\u00f6rleri ve ki\u015fisel ya\u015fam tarz\u0131, kanserin engellenmesinde g\u00fcn\u00fcm\u00fcz bilgileri dahilinde ba\u015fat rol\u00fcn\u00fc s\u00fcrd\u00fcrmektedir. Sigara i\u00e7iminin azalmas\u0131yla akci\u011fer kanser oranlar\u0131n\u0131n azalmas\u0131, Hepatit B a\u015f\u0131lamas\u0131n\u0131n yayg\u0131nla\u015fmas\u0131 ile hepatosell\u00fcler karsinom oranlar\u0131n\u0131n d\u00fc\u015f\u00fc\u015f\u00fc buna \u00f6rnektir.<\/p>\n

Kanser etyolojisindeki \u201cbilinmez\u201d bo\u015fluklar \u201c\u015fanss\u0131zl\u0131k\u201dla a\u00e7\u0131klanamayacak kadar b\u00fcy\u00fckt\u00fcr. K\u0131s\u0131tl\u0131 kaynaklar\u0131n bu bo\u015fluklar\u0131 hakk\u0131nca dolduracak ara\u015ft\u0131rmalara aktar\u0131lmas\u0131 WHO\u2019nun ana politikas\u0131 olmaya devam edecektir.<\/p>\n

Ara\u015ft\u0131rma sonu\u00e7lar\u0131n\u0131n yaratt\u0131\u011f\u0131 tart\u0131\u015fmalar yine de farkl\u0131 pencerelerden bakmam\u0131z\u0131 sa\u011fl\u0131yor. Ve rastlant\u0131sall\u0131k kanser konusunda her ne kadar \u201c\u00fcrk\u00fct\u00fcc\u00fc\u201d g\u00f6r\u00fcnse de kanser hastalar\u0131na, onlar\u0131n bir su\u00e7u olmad\u0131\u011f\u0131n\u0131 s\u00f6ylemesi a\u00e7\u0131s\u0131ndan \u00f6nemli g\u00f6r\u00fcn\u00fcyor.<\/u><\/p>\n","protected":false},"excerpt":{"rendered":"

Ortal\u0131\u011f\u0131 kar\u0131\u015ft\u0131ran makale 2 Ocak tarihli Science dergisinde yer ald\u0131. \u00c7al\u0131\u015fma, kanser tiplerinin g\u00f6r\u00fclme s\u0131kl\u0131\u011f\u0131 aras\u0131ndaki farkl\u0131l\u0131\u011f\u0131n \u201c\u015fanss\u0131zl\u0131\u011fa\u201d ba\u011fl\u0131 olabilece\u011fini iddia ediyordu. Nas\u0131l olur da rasgele mutasyonun yol a\u00e7t\u0131\u011f\u0131 \u201c\u015fanss\u0131zl\u0131k\u201d, ki\u015finin geneti\u011fi, ya\u015fam tarz\u0131, \u00e7evresel fakt\u00f6rler ile k\u0131yaslanabilirdi? Bu y\u0131l\u0131n ba\u015f\u0131nda Science dergisinde yay\u0131mlanan bir makale, kanser konusunda var olan bilgilerimizde sars\u0131c\u0131 bir etki yapt\u0131. […]<\/p>\n","protected":false},"author":42,"featured_media":23048,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[170,21,231,33],"tags":[2094,1631,444],"class_list":["post-23046","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-133-sayi","category-biyoloji","category-molekuler-biyoloji-ve-genetik","category-saglik-bilimleri","tag-genler","tag-hastalik","tag-kanser"],"acf":[],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t