The present invention provides a novel pharmaceutical composition for treating and/or preventing a cancer comprising, as an active ingredient, a polynucleotide derived from various miRNAs associated with cancer, a combination drug of the pharmaceutical composition and another antitumor agent, and a method for treating or preventing a cancer in a subject having the cancer using the pharmaceutical composition or the combination drug. The present invention relates to a pharmaceutical composition for treating and/or preventing a cancer comprising, as an active ingredient, a polynucleotide comprising the nucleotide sequence as set forth in SEQ ID NO: 1 or 2 (wherein when at least a part of the polynucleotide is DNA, uracil in a region corresponding to the DNA in the nucleotide sequence is replaced with thymine).