PROBLEM TO BE SOLVED: To provide pharmaceutical compositions for treating cancer patients who are predicted to benefit from the therapeutic administration of Wnt antagonist inhibitors.SOLUTION: The invention provides a pharmaceutical composition comprising a Wnt inhibitor for such a patient that, in following biomarkers (i) to (iv), the tumor has a reduced copy number of RNF43 or ZNRF3, or has an inactivation mutation of RNF43 or ZNRF3, or reduced expression of RNF43 mRNA or protein or reduced expression of ZNRF3 mRNA or protein, where the biomarkers are: (i) DNA copy number of RNF43 chromosomal region and/or ZNRF3 chromosomal region for determining a loss of heterozygosity; (ii) sequenced genomic DNA, cDNA or RNA from a cancer tissue for detecting inactivation mutation in RNF43 gene and/or ZNRF3 gene; (iii) RNF43 mRNA expression and/or ZNRF3 mRNA expression; and (iv) RNF43 protein expression and/or ZNRF3 protein expression.SELECTED DRAWING: None【課題】Wnt阻害剤が有効であると予測されるがん患者を治療するための医薬組成物の提供。【解決手段】バイオマーカー(i)~(iv)において、腫瘍がRNF43もしくはZNRF3のコピー数の減少を有するか、RNF43もしくはZNRF3の不活性化変異を有するか、又はRNF43 mRNAもしくはタンパク質の発現の減少又はZNRF3 mRNAもしくはタンパク質の発現の減少を有する患者の為の、Wnt阻害剤を含む医薬組成物。(i)ヘテロ接合性の消失を決定するための、RNF43染色体領域及び/又は該領域におけるDNAコピー数;(ii)RNF43遺伝子及び/又はZNRF3遺伝子の不活性化変異を検出するために配列決定されたがん組織からのゲノムDNA、cDNA又はRNA;(iii)RNF43 mRNA発現及び/又はZNRF3 mRNA発現;(iv)RNF43タンパク質発現及び/又はZNRF3タンパク質発現。【選択図】なし