BACKGROUND: Cancer stem-like cells (CSCs) represent a subset of tumor cells that have the ability to self-renew, a long lifespan and a relatively quiescent phenotype, and show resistance to conventional therapies. Various markers are used to identify CSCs, and have shown that different CSC subtypes may be present within a tumor. One functional property of CSCs is their relative lack of proteasomal activity compared to the tumor bulk. METHODS: We introduced an unstable fluorescent molecule into FaDu oropharyngeal squamous cell carcinoma cells and analyzed the association of proteasome activity with aldehydehyde dehydrogenase (ALDH) activity as another common CSC marker, and with other stem-cell related properties of glucose metabolism. We also analyzed publicly available gene expression profiling data of ALDH+ CSCs for alterations in mRNAs associated with proteostasis. RESULTS: We show that FaDu CSCs identified by low proteasome activity are associated with the population identified by high ALDH activity. Futher characterization shows that these CSCs have a relatively high mitochondrial membrane potential and low levels of glucose transporter, indicating a non-Warburg metabolic phenotype. We also show that proteasome-low FaDu CSCs exhibit decreased rates of protein synthesis. Gene expression profiling of other cancer cell lines reveal common statistically significant differences in proteostasis in ALDH+ CSCs compared to the bulk of the tumor cells, including reduced levels of Hsp70 and/or Hsp90 in CSCs defined by ALDH, together with reduced levels of UCHL5 mRNA. CONCLUSIONS: These data provide additional insights into the functional characteristics of proteasome-low/ALDH-high CSCs, indicating a metabolic phenotype of reduced reliance on aerobic glycolysis and a decreased protein synthesis rate. We also identify specific chaperone and ubiquitin ligase activities that can be used to identify CSCs, with corresponding implications for therapeutic strategies that target CSCs through their altered metabolic properties.

• Keywords
• Cancer stem cells, Glucose transporter, Mitochondrial membrane potential, Protein degradation, Proteosynthesis, Squamous cell carcinoma,
• MeSH
• Aldehyde Dehydrogenase * metabolism   genetics   MeSH
• Glucose metabolism   MeSH
• Humans MeSH
• Membrane Potential, Mitochondrial MeSH
• Mitochondria * metabolism   MeSH
• Cell Line, Tumor MeSH
• Neoplastic Stem Cells * metabolism   pathology   MeSH
• Proteasome Endopeptidase Complex metabolism   MeSH
• Glucose Transport Proteins, Facilitative * metabolism   MeSH
• Gene Expression Regulation, Neoplastic MeSH
• Carcinoma, Squamous Cell * metabolism   pathology   genetics   MeSH
• Gene Expression Profiling MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Aldehyde Dehydrogenase * MeSH
• Glucose MeSH
• Proteasome Endopeptidase Complex MeSH
• Glucose Transport Proteins, Facilitative * MeSH

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

Like other malignancies, prostate tumors are thought to contain cancer stem-like cells (CSCs) that are responsible for growth, metastasis, and therapy resistance. ΔNp63 (also called p40) is a regulator of normal prostate stem/progenitor cell activities and a marker of normal basal epithelial cells. The levels of ΔNp63 are reduced in prostate adenocarcinomas, although there is also evidence that ΔNp63 is involved in CSC regulation and drives metastasis to the bone. We studied metastatic deposits of prostate cancers with isoform-specific ΔNp63 and TAp63 antibodies. We identified p63-positive cells in only 3 of 42 metastatic prostate tumors (7%), including 2/38 (5.3%) "usual-type" adenocarcinomas. ΔNp63 and TAp63 isoforms were present in the nuclei of a small subpopulation (< 1%) of tumor cells in these metastases. ΔNp63-positive cells showed a basal-like cell phenotype (cytokeratin 8- and androgen receptor-negative, high molecular weight cytokeratin- and cytokeratin 19-positive), distinct from the tumor bulk. TAp63-positive cells were similar but were sometimes cytokeratin 8-positive. A subset of ΔNp63-positive tumor cells were CD44-positive, a marker of "basal" CSCs but were not positive for the "epithelial" CSC marker ALDH1. TAp63 was not associated with either of these CSC markers. None of the tumors containing p63-positive cells showed evidence of bone metastasis, compared with 28% of the p63-negative tumors. These data show that both ΔNp63 and TAp63 are present in only a small proportion of prostate adenocarcinomas and do not associate with metastasis. The data suggest heterogeneity of CSCs in prostate cancer, similar to other cancer types.

• Keywords
• CD44, Cancer stem cells, Metastasis, Prostate cancer, p40, p63,
• MeSH
• Adenocarcinoma metabolism   secondary   MeSH
• Adult MeSH
• Phenotype MeSH
• Middle Aged MeSH
• Humans MeSH
• Biomarkers, Tumor metabolism   MeSH
• Neoplastic Stem Cells metabolism   pathology   MeSH
• Tumor Suppressor Proteins metabolism   MeSH
• Bone Neoplasms metabolism   secondary   MeSH
• Prostatic Neoplasms metabolism   pathology   MeSH
• Retrospective Studies MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Case-Control Studies MeSH
• Transcription Factors metabolism   MeSH
• Check Tag
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Male MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Biomarkers, Tumor MeSH
• Tumor Suppressor Proteins MeSH
• TP63 protein, human MeSH Browser
• Transcription Factors 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