Signal transducer and activator of transcription 3 (Stat3) is responsible for many aspects of normal development and contributes to the development and progression of cancer through regulating epithelial cell identity and cancer stem cells. In breast cancer, Stat3 is associated with triple-negative breast cancers (TNBC) and its function has been related to the activation of p63, itself a marker of basal-like TNBC and a master regulator of stem cell activities. Stat3 activation is controlled by dual phosphorylation at tyrosine 705 (pTyr705) and serine 727 (pSer727), although it is unclear whether these have equivalent effects, and whether they are related or independent events. To address these issues, we investigated Stat3 phosphorylation at the two sites by immunohistochemistry in 173 patients with TNBC. Stat3 phosphorylation was assessed by automated quantitative measurements of digitized scanned images and classified into four categories based on histoscore. The results were analyzed for associations with multiple markers of tumor phenotype, proliferation, BRCA status, and clinicopathological characteristics. We show that the levels of pTyr705- and pSer727-Stat3 were independent in 34% of tumors. High pTyr705-Stat3 levels were associated with the luminal differentiation markers ERβ/AR and MUC1, whereas tumors with high levels of pSer727-Stat3 were more likely to be positive for the basal marker CK5/6, but were independent of p63 and were EGFR negative. Combined high pSer727- and low Tyr705-Stat3 phosphorylation associated with basal-like cancer. Although high Stat3 phosphorylation levels were associated with less aggressive tumor characteristics, they did not associate with improved survival, indicating that Stat3 phosphorylation is an unfavorable indicator for tumors with an otherwise good prognosis according to clinicopathological characteristics. These findings also show that pTyr705-Stat3 and pSer727-Stat3 associate with specific breast tumor phenotypes, implying that they exert distinct functional activities in breast cancer.

• Keywords
• Stat3 serine phosphorylation, Stat3 tyrosine phosphorylation, clinicopathological characteristics, triple-negative breast cancer, tumor cell phenotypes,
• MeSH
• Phenotype MeSH
• Phosphorylation MeSH
• Humans MeSH
• Cell Line, Tumor MeSH
• Serine genetics   MeSH
• STAT3 Transcription Factor metabolism   MeSH
• Triple Negative Breast Neoplasms * pathology   MeSH
• Tyrosine genetics   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Serine MeSH
• STAT3 protein, human MeSH Browser
• STAT3 Transcription Factor MeSH
• Tyrosine MeSH

BACKGROUND: ΔNp63 overexpression is a common event in squamous cell carcinoma (SCC) that contributes to tumorigenesis, making ΔNp63 a potential target for therapy. METHODS: We created inducible TP63-shRNA cells to study the effects of p63-depletion in SCC cell lines and non-malignant HaCaT keratinocytes. DNA damaging agents, growth factors, signaling pathway inhibitors, histone deacetylase inhibitors, and metabolism-modifying drugs were also investigated for their ability to influence ΔNp63 protein and mRNA levels. RESULTS: HaCaT keratinocytes, FaDu and SCC-25 cells express high levels of ΔNp63. HaCaT and FaDu inducible TP63-shRNA cells showed reduced proliferation after p63 depletion, with greater effects on FaDu than HaCaT cells, compatible with oncogene addiction in SCC. Genotoxic insults and histone deacetylase inhibitors variably reduced ΔNp63 levels in keratinocytes and SCC cells. Growth factors that regulate proliferation/survival of squamous cells (IGF-1, EGF, amphiregulin, KGF, and HGF) and PI3K, mTOR, MAPK/ERK or EGFR inhibitors showed lesser and inconsistent effects, with dual inhibition of PI3K and mTOR or EGFR inhibition selectively reducing ΔNp63 levels in HaCaT cells. In contrast, the antihyperlipidemic drug lovastatin selectively increased ΔNp63 in HaCaT cells. CONCLUSIONS: These data confirm that ΔNp63-positive SCC cells require p63 for continued growth and provide proof of concept that p63 reduction is a therapeutic option for these tumors. Investigations of ΔNp63 regulation identified agent-specific and cell-specific pathways. In particular, dual inhibition of the PI3K and mTOR pathways reduced ΔNp63 more effectively than single pathway inhibition, and broad-spectrum histone deacetylase inhibitors showed a time-dependent biphasic response, with high level downregulation at the transcriptional level within 24 h. In addition to furthering our understanding of ΔNp63 regulation in squamous cells, these data identify novel drug combinations that may be useful for p63-based therapy of SCC.

• Keywords
• DNA damage, Growth factor signaling, Histone deacetylase inhibitors, Oncogene addiction, Squamous cell carcinoma, ΔNp63,
• MeSH
• Histone Deacetylase Inhibitors MeSH
• Carcinogenesis MeSH
• Humans MeSH
• Cell Line, Tumor MeSH
• Tumor Suppressor Proteins metabolism   MeSH
• Tumor Suppressor Protein p53 * genetics   MeSH
• Family MeSH
• Carcinoma, Squamous Cell * drug therapy   genetics   metabolism   MeSH
• Transcription Factors metabolism   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Histone Deacetylase Inhibitors MeSH
• Tumor Suppressor Proteins MeSH
• Tumor Suppressor Protein p53 * MeSH
• TP63 protein, human MeSH Browser
• Transcription Factors MeSH

While erlotinib is primarily administered to patients with non-small cell lung cancer with sensitizing epidermal growth factor receptor (EGFR) mutations, it is also prescribed to patients with wild type (wt) EGFR in higher lines of treatment. However, there is no predictive marker for erlotinib efficacy in patients with EGFR wt. Certain immunohistochemical (IHC) parameters, including thyroid transcription factor 1 (TTF1) and p63, have been reported to indicate predictive power in patients with EGFR wt. The present study focused on retrospective data from the University Hospital in Pilsen using the TULUNG register. TTF1 and p63 expression data were extracted from the hospital information system and merged with registry data to calculate progression-free survival (PFS) and overall survival (OS) rates. A cohort of 345 patients with adenocarcinoma (ADC) or squamous cell carcinoma (SCC) exhibited similar erlotinib efficacies when TTF1 and p63 were ignored. However, significant differences were reported in PFS and OS rates of a subgroup of 126 patients where TTF1 and p63 parameters were known. In a univariate analysis, group A (ADC TTF1+/p63-) achieved PFS of 2.6 months, group B (SSC TTF1-/p63+) 1.9 months and group C (did not fit into groups A or B, i.e., ADC TTF1-/p63+ or SCC TTF1+/p63-) 1.4 months (P=0.006). Median OS was 14.2, 19.1 and 5.3 months for A, B and C, respectively (P=0.002). Furthermore, a multivariate analysis demonstrated IHC markers to be the only significant parameters for PFS and OS. Group C had a negative prognostic factor for PFS [hazard ratio (HR), 1.812; P=0.02] and OS (HR=2.367; P=0.01). In conclusion, patients with EGFR wt and lung carcinomas without TTF1 and p63 expression typical for ADC (TTF1+/p633-) or SCC (TTF1-/p63+) do not appear to be suitable candidates for erlotinib treatment.

• Keywords
• erlotinib, non-small cell lung cancer, p63, prediction, prognostic, thyroid transcription factor one,
• Publication type
• Journal Article MeSH

ΔNp63, also known as p40, regulates stemness of normal mammary gland epithelium and provides stem cell characteristics in basal and HER2-driven murine breast cancer models. Whilst ΔNp63/p40 is a characteristic feature of normal basal cells and basal-type triple-negative breast cancer, some receptor-positive breast cancers express ΔNp63/p40 and its overexpression imparts cancer stem cell-like properties in ER+ cell lines. However, the incidence of ER+ and HER2+ tumours that express ΔNp63/p40 is unclear and the phenotype of ΔNp63/p40+ cells in these tumours remains uncertain. Using immunohistochemistry with p63 isoform-specific antibodies, we identified a ΔNp63/p40+ tumour cell subpopulation in 100 of 173 (58%) non-triple negative breast cancers and the presence of this population associated with improved survival in patients with ER- /HER2+ tumours (p = 0.006). Furthermore, 41% of ER+ /PR+ and/or HER2+ locally metastatic breast cancers expressed ΔNp63/p40, and these cells commonly accounted for <1% of the metastatic tumour cell population that localised to the tumour/stroma interface, exhibited an undifferentiated phenotype and were CD44+ /ALDH- . In vitro studies revealed that MCF7 and T47D (ER+ ) and BT-474 (HER2+ ) breast cancer cell lines similarly contained a small subpopulation of ΔNp63/p40+ cells that increased in mammospheres. In vivo, MCF7 xenografts contained ΔNp63/p40+ cells with a similar phenotype to primary ER+ cancers. Consistent with tumour samples, these cells also showed a distinct location at the tumour/stroma interface, suggesting a role for paracrine factors in the induction or maintenance of ΔNp63/p40. Thus, ΔNp63/p40 is commonly present in a small population of tumour cells with a distinct phenotype and location in ER+ and/or HER2+ human breast cancers.

• Keywords
• CD44, HER2, aldehyde dehydrogenase, breast, cancer stem cells, oestrogen receptor, p40, p63, ΔNp63,
• MeSH
• Phenotype MeSH
• Heterografts MeSH
• Humans MeSH
• Mice MeSH
• Biomarkers, Tumor analysis   metabolism   MeSH
• Neoplastic Stem Cells metabolism   pathology   MeSH
• Tumor Suppressor Proteins metabolism   MeSH
• Breast Neoplasms genetics   metabolism   pathology   MeSH
• Receptor, ErbB-2 genetics   metabolism   MeSH
• Receptors, Estrogen genetics   metabolism   MeSH
• Transcription Factors metabolism   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• ERBB2 protein, human MeSH Browser
• Biomarkers, Tumor MeSH
• Tumor Suppressor Proteins MeSH
• Receptor, ErbB-2 MeSH
• Receptors, Estrogen MeSH
• TP63 protein, human MeSH Browser
• Transcription Factors MeSH

Signal Transducer and Activator of Transcription 3 (STAT3) is a transcription factor with many important functions in the biology of normal and transformed cells. Its regulation is highly complex as it is involved in signaling pathways in many different cell types and under a wide variety of conditions. Besides other functions, STAT3 is an important regulator of normal stem cells and cancer stem cells. p63 which is a member of the p53 protein family is also involved in these functions and is both physically and functionally connected with STAT3. This review summarizes STAT3 function and regulation, its role in stem cell and cancer stem cell properties and highlights recent reports about its relationship to p63.

• Keywords
• Cancer stem cells, STAT3, Stem cells, p63,
• MeSH
• Phosphorylation MeSH
• Humans MeSH
• Human Embryonic Stem Cells metabolism   MeSH
• Methylation MeSH
• MicroRNAs metabolism   MeSH
• Mouse Embryonic Stem Cells metabolism   MeSH
• Mice MeSH
• Neoplastic Stem Cells metabolism   MeSH
• Tumor Suppressor Proteins chemistry   metabolism   MeSH
• Neoplasms metabolism   MeSH
• Cellular Reprogramming MeSH
• STAT3 Transcription Factor chemistry   metabolism   MeSH
• Transcription Factors chemistry   metabolism   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• MicroRNAs MeSH
• Tumor Suppressor Proteins MeSH
• TP63 protein, human MeSH Browser
• STAT3 Transcription Factor MeSH
• Transcription Factors MeSH

The TP63 gene encodes two major protein variants that differ in their N-terminal sequences and have opposing effects. In breast, ΔNp63 is expressed by immature stem/progenitor cells and mature myoepithelial/basal cells and is a characteristic feature of basal-like triple-negative breast cancers (TNBCs). The expression and potential role of TAp63 in the mammary gland and breast cancers is less clear, partly due to the lack of studies that employ p63 isoform-specific antibodies. We used immunohistochemistry with ΔNp63-specific or TAp63-specific monoclonal antibodies to investigate p63 isoforms in 236 TNBCs. TAp63, but not ΔNp63, was seen in tumour-associated lymphocytes and other stromal cells. Tumour cells showed nuclear staining for ΔNp63 in 17% of TNBCs compared to 7.3% that were positive for TAp63. Whilst most TAp63+ tumours also contained ΔNp63+ cells, the levels of the two isoforms were independent of each other. ΔNp63 associated with metaplastic and medullary cancers, and with a basal phenotype, whereas TAp63 associated with androgen receptor, BRCA1/2 wild-type status and PTEN positivity. Despite the proposed effects of p63 on proliferation, Ki67 did not correlate with either p63 isoform, nor did they associate with p53 mutation status. ΔNp63 showed no association with patient outcomes, whereas TAp63+ patients showed fewer recurrences and improved overall survival. These findings indicate that both major p63 protein isoforms are expressed in TNBCs with different tumour characteristics, indicating distinct functional activities of p63 variants in breast cancer. Analysis of individual p63 isoforms provides additional information into TNBC biology, with TAp63 expression indicating improved prognosis.

• Keywords
• Androgen receptor, BRCA1, BRCA2, PTEN, TAp63, Triple-negative breast cancer, ΔNp63,
• MeSH
• Phenotype MeSH
• PTEN Phosphohydrolase genetics   MeSH
• Humans MeSH
• Neoplasm Recurrence, Local genetics   MeSH
• Mutation genetics   MeSH
• Tumor Suppressor Proteins genetics   MeSH
• Protein Isoforms genetics   MeSH
• BRCA1 Protein genetics   MeSH
• BRCA2 Protein genetics   MeSH
• Gene Expression Regulation, Neoplastic genetics   MeSH
• Transcription Factors genetics   MeSH
• Triple Negative Breast Neoplasms genetics   metabolism   mortality   MeSH
• Check Tag
• Humans MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• BRCA1 protein, human MeSH Browser
• BRCA2 protein, human MeSH Browser
• PTEN Phosphohydrolase MeSH
• Tumor Suppressor Proteins MeSH
• Protein Isoforms MeSH
• BRCA1 Protein MeSH
• BRCA2 Protein MeSH
• PTEN protein, human MeSH Browser
• TP63 protein, human MeSH Browser
• Transcription Factors MeSH