( ( ( ( ( ( Exposure ( to ( radiation ( or ( cancer-causing chemicals ) ) ) ) ) ( may ( ( cause ( DNA mutations ) ) ( in ( many organs ) ) ) ) ) , ) but ) ( ( these factors ) ( ( have not ) ( been ( proven ( to ( be ( ( important causes ) ( of ( mutations ( in ( prostate cells ) ) ) ) ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (NP (NNP Exposure)) (PP (TO to) (NP (NN radiation) (CC or) (JJ cancer-causing) (NNS chemicals)))) (VP (MD may) (VP (VB cause) (NP (NN DNA) (NNS mutations)) (PP (IN in) (NP (JJ many) (NNS organs)))))) (, ,) (CC but) (S (NP (DT these) (NNS factors)) (VP (VBP have) (RB not) (VP (VBN been) (VP (VBN proven) (S (VP (TO to) (VP (VB be) (NP (NP (JJ important) (NNS causes)) (PP (IN of) (NP (NP (NNS mutations)) (PP (IN in) (NP (NN prostate) (NNS cells))))))))))))) (. .)))
Exposure to radiation or cancer-causing chemicals may cause DNA  mutations in many organs, but these factors have not been proven to be important causes of mutations in prostate cells.
(ROOT (S (NP (NNP Cancer)) (VP (VBZ is) (VP (VBN caused) (PP (IN by) (NP (NP (NNS mutations)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (MD can) (VP (VB be) (VP (VBN caused) (PP (IN by) (NP (NNS pathogens) (, ,) (NNS chemicals) (, ,) (CC or) (NN radiation)))))))))))) (. .)))