some help with this articles figure legend

from the article CRISPR-Cas9: a new and promising player in gene therapy

CRISPR-Cas9-mediated gene (in)activation in cancer cells. (A) The expression of single guide RNAs (sgRNAs) and Cas9 are controlled by cancer-specific promoter and tissue-specific promoter, respectively. Consequently, only in the specific cancer cells can express both of them. (B) The sgRNAs are designed to target LacI gene or oncogene. (C) In normal cells, LacI protein expressed by LacI gene binds to Lac operator and suppresses the expression of the downstream effector gene. In specific cancer cells, Cas9 and sgRNAs are both expressed, mutating LacI gene and abrogating its suppression on the effector gene, leading to its cancer-specific expression. (D) Loss-of-function mutation of oncogene in cancer cells induced by CRISPR-Cas9 editing. (This figure is partially based on the study by Liu et al47).

im a little confused,, why in the normal cells is the oconsupressor inactived, i would suspect that in cancer cells because the inactivation of this supressor would allow the tumor to grow.. thank you for your help