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Colorectal cancer (CRC) is the second most common cancer in women and the third most common in men. Adenocarcinoma accounts for 90% of CRC cases. There has been accumulating evidence in support of the cancer stem cell (CSC) concept of cancer which proposes that CSCs are central in the initiation of cancer. CSCs have been the focus of study in a range of cancers, including CRC. This has led to the identification and understanding of genes involved in the induction and maintenance of pluripotency of stem cells, and markers for CSCs, including those investigated specifically in CRC. Knowledge of the expression pattern of CSCs in CRC has been increasing in recent years, revealing a heterogeneous population of cells within CRC ranging from pluripotent to differentiated cells, with overlapping and sometimes unique combinations of markers. This review summarises current literature on the understanding of CSCs in CRC, including evidence of the presence of CSC subpopulations, and the stem cell markers currently used to identify and localise these CSC subpopulations. Future research into this field may lead to improved methods for early detection of CRC, novel therapy and monitoring of treatment for CRC and other cancer types., Competing Interests: Competing interests: TI and STT are inventors of the PCT patent application (No. PCT/NZ2015/050108) Cancer Diagnosis and Therapy, and Cancer Therapeutic (US62/452479). The authors declare no other conflicts of interest., (© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

The stem cell markers octamer-binding transcription factor 4, sex-determining region Y-box 2, NANOG, Kruppel-like factor 4 and c-MYC are key factors in inducing pluripotency in somatic cells, and they have been used to detect cancer stem cell subpopulations in a range of cancer types. Recent literature has described the subcellular localisation of these markers and their potential implications on cellular function. This is a relatively complex and unexplored area of research, and the extent of the effect that subcellular localisation has on cancer development and growth is largely unknown. This review analyses this area of research in the context of the biology of stem cells and cancer and explores the potential modulating effect of subcellular localisation of these proteins as supported by the literature., Competing Interests: Competing interests: TI, STT and PFD are inventors of the PCT patent applications (NZ2015/050108) Cancer Diagnosis and Therapy, and Cancer Therapeutic (US62/452479). The authors are otherwise not aware of any commercial associations or financial relationships that might create a conflict of interest with any information presented in this manuscript., (© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

Aims: To identify, characterise and localise the population of primitive cells in keloid scars (KS)., Methods: 5-µm-thick formalin-fixed paraffin-embedded sections of KS samples from 10 patients underwent immunohistochemical (IHC) staining for the embryonic stem cell (ESC) markers OCT4, SOX2, pSTAT3 and NANOG, and keloid-associated lymphoid tissue (KALT) markers CD4 and CD20. NanoString gene expression analysis and in situ hybridisation (ISH) were used to determine the abundance and localisation of the mRNA for these ESC markers., Results: IHC staining revealed the expression of the ESC markers OCT4, SOX2, pSTAT3 and NANOG by a population of cells within KS tissue. These are localised to the endothelium of the microvessels within the KALTs. NanoString gene expression analysis confirmed the abundance of the transcriptional expression of the same ESC markers. ISH localised the expression of the ESC transcripts to the primitive endothelium in KS tissue., Conclusions: This report demonstrates the expression of ESC markers OCT4, SOX2, pSTAT3 and NANOG by the endothelium of the microvessels within the KALTs. These findings show a unique niche of primitive cells within KS, expressing ESC markers, revealing a potential therapeutic target in the treatment of KS., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/)

Aims: Interstitial CD45+ cells and T lymphocytes have previously been demonstrated within infantile haemangioma (IH). This study investigated the expression of B and T lymphocyte markers by the CD45+ population, and the expression of Thy-1, a marker of thymocyte progenitors, which have the ability to give rise to both B and T cells., Methods: Immunohistochemical (IHC) staining was performed on proliferating and involuted IHs for the expression of CD45, CD3, CD20, CD79a, Thy-1 and CD34. The presence of mRNA corresponding to CD45, CD3G, CD20 and Thy-1 was confirmed by reverse transcriptase-polymerase chain reaction in snap-frozen IH tissues. Cell counting of 3,3-diaminobenzidine IHC-stained slides was performed on CD45+ only cells and dually stained CD45+/CD3+ cells or CD45+/CD20+ cells and analysed statistically. In situ hybridisation and mass spectrometry were also performed to confirm the presence and abundance of Thy-1, respectively., Results: IHC staining showed a subpopulation of CD45+ interstitial cells that expressed the T lymphocyte marker, CD3, and another subpopulation that expressed the B lymphocyte marker, CD20, in proliferating and diminished in involuted IHs. The abundant expression of Thy-1 on the endothelium of proliferating, but not involuted IH, was demonstrated by IHC staining and confirmed by in situ hybridisation and mass spectrometry., Conclusions: Both B and T lymphocytes are present within the interstitium of proliferating and involuted IH. The expression of Thy-1 by the endothelium suggests that B and T cells in IH may have originated from within the lesion, rather than migrating from the peripheral circulation., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.)

Aims: Cells expressing markers of mast cells, macrophages and dendritic cells have previously been demonstrated within the interstitium of infantile haemangioma (IH). This study characterised these myeloid cellular subpopulations within IH., Methods: Immunohistochemical staining was performed on proliferating and involuted IHs for the expression of Nanog, tryptase, CD163, DC-SIGN and CD45. The presence of mRNA corresponding to Nanog, tryptase α/β-1, tryptase β-2, CD163 and DC-SIGN was confirmed by NanoString and RT-PCR in snap-frozen IH tissues., Results: Immunohistochemical staining showed expression of Nanog by interstitial phenotypical mast cells within proliferating IH, which were separate from the interstitial M2-polarised macrophages that also expressed DC-SIGN, a dendritic cell marker. These two myeloid cellular subpopulations in IH did not express the pan-haematopoietic marker, CD45., Conclusions: There are two interstitial subpopulations of myeloid cells within IH: phenotypical mast cells which also express Nanog, indicating a primitive phenotype; and M2-polarised macrophages which also express DC-SIGN., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.)

Aims: To investigate the effect of the angiotensin peptides and their agonists and antagonists on cellular proliferation in proliferating infantile haemangioma (IH) in vitro explants., Methods: Proliferating IH samples from six patients were cultured in vitro in the presence of angiotensin I (ATI) alone, or AT1 and the ACE inhibitor, ramipril, or ATII alone, or ATII with the ATII receptor 1 (ATIIR1) blocker, losartan, or ATII with the ATIIR2 blocker, PD123319, or the ATIIR2 agonist, CGP42112. After 6 days in culture, the IH tissue pieces were harvested, formalin-fixed and paraffin-embedded. The effect of each treatment type on cellular proliferation was evaluated by immunohistochemical staining of these tissue pieces using the proliferation marker, Ki67., Results: There was a significant increase in cellular proliferation in the ATI and ATII treated IH tissues compared with control samples. Their effect on cellular proliferation was reduced by adding ramipril and PD123319, respectively. CGP42112, but not losartan, significantly increased cellular proliferation., Conclusions: Our findings suggest a key regulatory role of ATI and ATII in promoting cellular proliferation in IH, and establish a role for ACE and ATIIR2 in the proliferation of this tumour., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.)

Aims: Recent reports on infantile haemangioma (IH) have demonstrated a primitive population of interstitial cells expressing the embryonic transcription factor, Nanog, with decreasing abundance during involution. In this report we investigated the expression of Nanog on mast cells in all three phases of IH progression., Methods: Paraffin-embedded sections of six proliferating, six involuting and six involuted IH lesions were used to investigate the expression of tryptase, Nanog, CD45, CD34 and GLUT-1 by immunostaining., Results: Mast cells, identified by their expression of tryptase, were located in the interstitium of IH lesions. 93%, 42% and 0% of these tryptase(+) cells also expressed Nanog, in proliferating, involuting and involuted IH, respectively., Conclusions: The identification of an abundant population of tryptase(+)/Nanog(+) cells in IH is novel. The relative loss of Nanog expression as IH involutes may be a result of maturation and/or proliferation of these cells. This report supports the primitive nature of IH.

Background: The origin of infantile haemangioma (IH) remains enigmatic. A primitive mesodermal phenotype origin of IH with the ability to differentiate down erythropoietic and terminal mesenchymal lineages has recently been demonstrated., Aims: To investigate the expression of human embryonic stem cell (hESC) markers in IH and to determine whether IH-derived cells have the functional capacity to form teratoma in vivo., Methods: Immunohistochemical staining and quantitative reverse transcription PCR were used to investigate the expression of hESC markers in IH biopsies. The ability of cells derived from proliferating IH to form teratomas in a mouse xenograft model was investigated., Results: The hESC markers, Oct-4, STAT-3 and stage-specific embryonic antigen 4 were collectively expressed on the endothelium of proliferating IH lesions, whereas Nanog was not. Nanog was expressed by cells in the interstitium and these cells did not express Oct-4, stage-specific embryonic antigen 4 or STAT-3. Proliferating IH-derived cells were unable to form teratomas in severely compromised immunodeficient/non-obese diabetic mice., Conclusion: The novel expression of hESC on two different populations of cells in proliferating IH and their inability to form teratomas in vivo infer the presence of a primitive cellular origin for IH downstream from hESC.

Aims: To investigate the expression of the placental cell-specific associated proteins in infantile haemangioma (IH)., Methods: Immunohistochemical staining was used to investigate the expression of human chorionic gonadotrophin (hCG), human placental lactogen (hPL), human leucocyte antigen-G (HLA-G), cytokeratin 7 (CK7) and smooth muscle actin in paraffin-embedded sections of proliferating and involuted IHs., Results: The proteins hCG and hPL were expressed by the endothelium but not the pericyte layer of proliferating IH, but these proteins were not detected in involuted lesions. There was no expression of CK7 and HLA-G in IH., Conclusions: The expression of hCG and hPL, but not CK7 or HLA-G, by the endothelium of proliferating IH supports a placental chorionic villous mesenchymal core cellular origin for IH rather than a trophoblast origin.

Background: Fibro-fatty deposition commonly occurs during involution of infantile haemangioma (IH). Mesenchymal stem cells have been identified in this tumour and have been proposed to be recruited from the bone marrow and/or adjacent niches, and then give rise to the fibro-fatty tissue. The authors have recently demonstrated that the capillary endothelium of proliferating IH co-expresses primitive mesodermal, mesenchymal and neural crest markers and proposed that this same endothelium has the ability to give rise to cells of mesenchymal lineage that constitute the fibro-fatty deposition., Methods: Immunohistochemistry and real-time RT-PCR were used to further characterise proliferating IHs and haemangioma explant-derived cells (HaemEDCs)., Results: The authors have further confirmed expression of the mesenchymal-associated proteins including preadipocyte factor-1, a mesenchymal differentiation inhibition-associated cytokine. The HaemEDCs could be differentiated into osteoblasts and adipocytes, indicating their functional potential for terminal differentiation., Discussion: The collective expression of neural crest, mesenchymal and mesenchymal differentiation inhibition-associated proteins on the endothelium of proliferating IH suggests that the cells in the capillary endothelium within the lesion possess the ability to undergo terminal mesenchymal differentiation during the proliferating phase, but are inhibited from doing so.

Background: Proliferating infantile haemangioma (IH) is a tumour of the microvasculature composed predominantly of immature endothelial cells. The origin of IH is unclear, but it has been shown to express markers of both endothelial and haematopoietic lineages, and a role for endothelial progenitor cells in the aetiology of IH has been suggested. Haemangioblasts are precursors of both endothelial and haematopoietic cells, and their characterisation has identified the expression of cell surface and intracellular proteins that collectively can be used for assigning a haemangioblast phenotype., Methods: The authors used immunohistochemical staining to characterise the expression of primitive haematopoietic-associated proteins in proliferating IHs., Results and Discussion: The authors show that the cells forming the capillary endothelium express markers associated with primitive haematopoietic cells. Additionally, many of these cells express the transcription factors brachyury and GATA-2, indicating a primitive mesodermal origin. They hypothesise that the immature capillaries in IH are derived from primitive mesodermal cells with haemangioblastic differentiation capabilities. The expression of primitive mesodermal, endothelial and haematopoietic markers by the cells forming the endothelium suggests that the immature capillaries that predominate in proliferating IH are a haemogenic endothelium phenotype, derived from haemangioblasts.

Aims: Infantile haemangioma is a tumour of the microvasculature characterised by aggressive angiogenesis during infancy and spontaneously gradual involution, often leaving a fibro-fatty residuum. The segmental distribution of a subgroup of infantile haemangioma, especially those associated with midline structural anomalies that constitute posterior fossa malformations-hemangiomas-arterial anomalies-cardiac defects-eye abnormalities-sternal cleft and supraumbilical raphe syndrome (PHACES), led us to investigate whether neural crest cells might be involved in the aetiology of this tumour., Methods: Immunohistochemical staining on paraffin embedded infantile haemangioma sections and immunocytochemical staining on cells derived from proliferating haemangioma cultures were performed., Results: The endothelium of proliferating infantile haemangioma contains abundant cells that express the neurotrophin receptor (p75), a cell surface marker that identifies neural crest cells, and also for brachyury, a transcription factor expressed in cells of the primitive mesoderm. The endothelium is also immunoreactive for the haematopoietic stem cell marker, CD133; the endothelial-haematopoietic stem/progenitor marker, CD34; the endothelial cell markers, CD31 and VEGFR-2; and the mesenchymal stem cell markers, CD29 and vimentin. Additionally, immunoreactivity for the transcription factors, Sox 9 and Sox 10, that are expressed by prospective neural crest cells was also observed. Cells from microvessel-like structures were isolated from in vitro cultured haemangioma tissue explants embedded in a fibrin matrix. Immunostaining of these cells showed that they retained expression of the same lineage-specific markers that are detected on the paraffin embedded tissue sections., Conclusions: These data infer that infantile haemangioma is derived from primitive mesoderm and that the cells within the lesion have a neural crest stem cell phenotype, and they express proteins associated with haematopoietic, endothelial, neural crest and mesenchymal lineages. The authors propose a model to account for the natural progression of infantile haemangioma based upon the multipotent expression profile of the primitive mesoderm and their neural crest stem cell phenotype to form all the cell lineages detected during infantile haemangioma proliferation and involution.