Effect of crude C. majus latex (S1), protein fraction (S2), and alkaloid-rich fraction (S3) on the expression of the viral E7 oncogene at the protein level in HeLa cells. Non-toxic concentrations of crude latex, alkaloid-rich fraction, and protein fraction were administered on HeLa cells. After 48 h of incubation, proteins were isolated, which were then separated by SDS-PAGE. Immunodetection of the E6 protein and the GAPDH as a reference protein was performed using the Western blot and specific antibodies. The densitometric measurement showed that only the crude C. majus latex reduced the level of HPV E7 proteins in HeLa cells (a reduction of 86.6%). The alkaloid-rich fraction and the protein fraction had no effect on the level of E7 protein synthesis. S1—cells treated with crude latex, S2—cells treated with the protein fraction, S3—cells treated with the alkaloid-rich fraction, Control—untreated cells. (A) Representative Western blot of protein immunodetection. (B) Densitometric analysis using ImageJ software (NIH). *** p < 0.001.