Some Gene damage: Permanent

Some gene damage from smoking is permanent: study

Aug. 30, 2007
Courtesy BioMed Central
and World Science staff

A new study may help ex­plain why form­er smok­ers are still more prone to lung can­cer than those who have nev­er smoked. It found that smok­ing causes some per­ma­nent ge­ne­tic da­mage.

Quit­ting still of­fers huge health ben­e­fits, re­search­ers stressed, as the risk to form­er smok­ers is much low­er than for cur­rent smok­ers.

A team led by Wan Lam and Ste­phen Lam from the BC Can­cer Agen­cy in Van­cou­ver, Can­a­da, took sam­ples from the lungs of 24 cur­rent and form­er smok­ers, as well as from peo­ple who have nev­er smoked.

They used the sam­ples to cre­ate li­brar­ies us­ing a tech­nique called se­ri­al anal­y­sis of gene ex­pres­sion, which helps to iden­ti­fy pat­terns of gene ac­ti­vity.

Only about a fifth of the genes in a cell are switched on at any giv­en time, but smok­ing leads to changes in gene ac­ti­vity. The re­search­ers found that some of these changes, though not all, per­sisted even years af­ter quit­ting smok­ing.

The re­vers­i­ble genes were par­tic­u­larly in­volved in “xeno­bi­otic” func­tion­s—ma­nag­ing chem­i­cals not pro­duced in the body—and me­tab­o­lism of ge­net­ic ma­te­ri­al and mu­cus se­cre­tion, sci­en­tists found. The irre­vers­i­ble dam­age was to some DNA re­pair genes, and to the ac­ti­vity of genes that help fight lung can­cer de­vel­op­ment.

“Those genes and func­tions which do not re­vert to nor­mal lev­els up­on smok­ing cessa­t­ion may pro­vide in­sight in­to why form­er smok­ers still main­tain a risk of de­vel­op­ing lung can­cer,” said Raj Cha­ri, first au­thor of the stu­dy. To­bac­co smok­ing ac­counts for 85 per­cent of lung can­cers, and form­er smok­ers ac­count for half of those newly di­ag­nosed with the dis­ease.

The gene find­ings are pub­lished in the Aug. 29 is­sue of the on­line re­search jour­nal BMC Ge­nomics.