When the expression of the three transcription factors was confirmed by referring to the public database COSMIC (Catalogue of Somatic Mutations in Cancer), the expression level of the three transcription factors was not high in DMS 273 cells, which could belong to SCLC-I; in H1048 cells, POU2F3 was expressed in this way, which could be classified as SCLC-P. Here, POU2F3 is linked to cancer.