Repression of p63 and induction of EMT by mutant Ras in mammary epithelial cells

Abstract

The p53-related transcription factor p63 is required for maintenance of epithelial cell differentiation. We found that activated forms of the Harvey Rat Sarcoma Virus GTPase (H-RAS) and phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) oncogenes strongly repress expression of ΔNp63α, the predominant p63 isoform in basal mammary epithelial cells. This regulation occurs at the transcriptional level, and a short region of the ΔNp63 promoter is sufficient for repression induced by H-RasV12. The suppression of ΔNp63α expression by these oncogenes concomitantly leads to an epithelial-tomesenchymal transition (EMT). In addition, the depletion of ΔNp63α alone is sufficient to induce EMT. Both H-RasV12 expression and ΔNp63α depletion induce individual cell invasion in a 3D collagen gel in vitro system, thereby demonstrating how Ras can drive the mammary epithelial cell state toward greater invasive ability. Together, these results suggest a pathway by which RAS and PIK3CA oncogenes induce EMT through regulation of ΔNp63α.p63 | H-Ras | epithelial mesenchymal transition | transcriptional repression | breast cancer H -Ras, a member of the Ras family of GTPases, was originally identified as the transforming protein encoded by the Harvey rat sarcoma retrovirus (1). Activating mutations in H-Ras and its family members, K-Ras and N-Ras, were identified in a variety of cancers, and nearly 30% of all cancers have mutations in one of the Ras genes (2, 3). The EGFR2 receptor, also known as HER2/ neu, is an important upstream activator of Ras and is amplified in about 20-30% of breast cancers (4, 5). Although many HER2 + cancers are initially responsive to treatment with the monoclonal antibody Herceptin (trastuzumab), resistance usually develops (6, 7). Therefore, it is of great importance to understand signaling pathways that are downstream of HER2 and Ras, to identify key factors responsible for their tumor-promoting effects. It may also be possible to target such factors, in combination with HER2 or Ras inhibitors, to achieve greater clinical efficacy.A major effector downstream of Ras is the phosphatidylinositol 3-kinase (PI3K) pathway. The catalytic subunit of PI3K, PIK3CA, is frequently found mutated in cancers, especially those cancers originating in the breast (8, 9). Like mutant Ras, expression of mutant PIK3CA can cause nontumorigenic cells to undergo transformation and gain invasive abilities (10, 11). Carcinoma cells, in particular, may gain increased invasive abilities by undergoing an epithelial-to-mesenchymal transition (EMT), where adherens junctions formed by E-cadherin are disrupted (12, 13). Canonical transcription factors that repress E-cadherin include Twist, Snail, Slug, and Zeb1, although this network has grown more complex in recent years (14,15).The transcription factor p63 not only induces transcription of canonical p53 targets but is also a master regulator of epithelial cells (16,17). Mice losing both alleles of p63 display complications due to the loss of epithelial stratif...

Tn antigen promotes human colorectal cancer metastasis via H‐Ras mediated epithelial‐mesenchymal transition activation

“…We checked the expression profiles of Ras genes (H‐Ras, K‐Ras, N‐Ras) in Tn‐positive vs Tn‐negative CRC cells, and found an increased expression of H‐Ras in cancer cells expressing Tn antigen, whereas the changes of K‐Ras or N‐Ras were not different. Several studies revealed that ectopic expression of oncogenic H‐Ras led to an EMT and increased invasive ability, which were indeed consistent with our observations . We found that knockdown of H‐Ras resulted in a suppression of EMT and reduced the ability of cell migration and invasion, suggesting that H‐Ras could be a key factor responsible for Tn antigen‐induced cancer metastasis.…”

“…We further investigated the mechanisms by which Tn antigen activates EMT. Accumulating evidence shows that Ras signalling activates EMT during cancer metastasis . We reasoned whether Tn antigen has an influence on Ras family proteins (H‐Ras, K‐Ras and N‐Ras), and consequently, activates EMT.…”

Low‐grade spindle cell proliferation in clear cell renal cell carcinoma is unlikely to be an initial step in sarcomatoid differentiation

“…Claudins are suggested to be integral membrane proteins, responsible for maintaining epithelial cell polarity. Repression of p63, a transcription factor required for maintenance of epithelial cell differentiation, induces EMT …”

Frequency and Distribution of Cytoplasmic and Nuclear P63 in Recognizing the Basal-Like and Non-Basal-Like Types of Breast Cancer Based on Age.

“…One of the techniques used to conduct the prognosis is using a marker to detect immunohistochemically [2]. Marker not only has certain characteristic properties but also has predictive character toward the sensitivity and specificity of breast tumors with specific types [20,21]. TP63, on the other hand, is a nuclear marker of myoepithelial cells frequently expressed on basal epithelial cells of tumors.…”

“…The basal-like and TNBC were associated [19]. In addition, the expression of p63 protein derived from basal epithelial cells is strongly influenced by the intensity of tumor cell development such as cell nutrition factor [20], chemotherapy, regulation, and p63 protein synthesis [21] both in nucleus and cytoplasm [22].…”