Amreen Salwa

NKX3-2 Induces Ovarian Cancer Cell Migration by HDAC6-Mediated Repositioning of Lysosomes and Inhibition of Autophagy

Several soluble factors secreted by the stromal cells and cancer cells within the tumor microenvironment facilitate the progression and invasiveness of ovarian cancer. In ovarian cancer cells, lysophosphatidic acid (LPA) modulates the transcriptome profile and promotes cell invasiveness by the downregulation of autophagy. Here, we further elucidate this mechanism by focusing on the molecular and cellular events regulating autophagy. Transcriptomic and Western blotting analyses revealed NKX3-2, a transcriptional factor, to be among the genes hyperexpressed in LPA-stimulated ovarian cancer cells. Bioinformatic analyses revealed that in ovarian cancer patients, the expression of NKX3-2 positively correlates with genes involved in cell motility and migration, while it negatively correlates with macromolecular catabolic pathways. In various ovarian cancer cell lines, NKX3-2 silencing abrogated LPA-induced cell migration. Mechanistically, this effect is linked to the restoration of the HDAC6-mediated relocation of the lysosomes in the para-golgian area, and this results in an increase in autolysosome formation and the overall upregulation of autophagy. Silencing the expression of ATG7 or BECN1, two autophagy genes, rescued the migratory phenotype of the NKX3-2-silenced ovarian cancer cells. Taken together, these data reveal the mechanism by which the LPA-NKX3-2 axis promotes the invasiveness of ovarian cancer cells and supports the possibility of targeting NKX3-2 to reduce the migratory capacity of cancer cells in response to a permissive microenvironment.

P53-Induced Autophagy Degradation of NKX3-2 Improves Ovarian Cancer Prognosis

NKX3-2, a transcriptional repressor factor belonging to the NK family of homeobox-containing proteins, has been widely studied for its role in promoting chondrogenic differentiation and homeostasis. NKX3-2 is upregulated in chemoresistant ovarian tumors and metastatic gastric cancer cells; however, its prognostic role and mechanistic involvement in cancer cell biology remain to be elucidated. By interrogating the TCGA database, we found that cancer patients with high NKX3-2 expression had a shorter overall survival rate than patients with low expression. In ovarian cancer patients, NKX3-2 negatively correlates with P53. Given the prominent role of the latter oncosuppressor in controlling DNA repair and cell death, here we investigate the molecular mechanism involved in this negative correlation in several ovarian cancer cell lines expressing different levels of the two proteins. We found that the high expression of endogenous or ectopic P53 reduced NKX3-2 protein expression, while its knockdown increased it. In contrast, the genetic manipulation of NKX3-2 expression did not affect P53 expression. Mechanistically, P53-mediated downregulation of NKX3-2 does not entail transcriptional activity or proteasomal clearance but occurs via P53–NKX3-2 protein–protein interaction, which in turn results in P53-induced NKX3-2 degradation via the autophagy–lysosome pathway. Remarkably, patients bearing a tumor characterized by low NKX3-2 and high MAP1LC3B expression (indicative of active autophagy) display a better prognosis. Taken together, our data indicate that NKX3-2 represents a negative prognostic factor under P53 control in ovarian cancer. From a translational point of view, identifying this novel mechanism may represent a new molecular signature capable of predicting the clinical outcome of patients, a crucial aspect of developing personalized therapeutic approaches.