THOC2 or THOC5 knockdown suppresses the tumorigenicity of radioresistant TNBC in vivo. A) THOC2‐ or THOC5‐silenced MDA‐MB‐231‐RR cells were subcutaneously injected into the nude mice. The xenograft tumors derived from these MDA‐MB‐231‐RR cells were photographed and compared at the end of the experiment. B) Tumor growth was monitored every 4 days for 8 weeks, and the volume was recorded till the experiment ended. C) Tumor weight was measured and compared at the end of the experiment. D) Tumor incidence in mice transplanted with MDA‐MB‐231‐RR cells expressing sh‐control, sh‐THOC2, or sh‐THOC5 was shown and, a limiting dilution method was used to examine the frequency of CSCs in tumors. E) The protein level of THOC2, THOC5, NANOG, SOX2, and Ki‐67 in xenograft tumors was detected by IHC. Representative IHC images are shown at 200× magnification. ***P < 0.001 versus sh‐control group (n = 8).