CTSG and lung cancer: The statistical results of this experiment showed that the level of CTSG protein expression was not related to the sex, age, smoking history, whether HIV RNA could be detected after the first consultation, and lymph node metastasis of the patients with HIV-related lung cancer (P>0.05); however, it was closely related to the pathological type of HIV-related lung cancer, distant metastasis, and clinical stage, and the difference was statistically significant (P<0.05) (Table 3).