ALDH1A1+ ovarian cancer stem cells co-expressing surface markers CD24, EPHA1 and CD9 form tumours in vivo.

One of the reasons for recurrence following treatment of high grade serous ovarian carcinoma (HGSOC) is the persistence of residual cancer stem cells (CSCs). There has been variability between laboratories in the identification of CSC markers for HGSOC. We have identified new surface markers (CD24, CD9 and EPHA1) in addition to those previously known (CD44, CD117 and CD133) using a bioinformatics approach. The expression of these surface markers was evaluated in ovarian cancer cell lines, primary malignant cells (PMCs), normal ovary and HGSOC. There was no preferential expression of any of the markers or a combination. All the markers were expressed at variable levels in ovarian cancer cell lines and PMCs. Only CD117 and CD9 were expressed in the normal ovarian surface epithelium and fallopian tube. Both ALDEFLUOR (ALDH1A1) and side population assays identified a small proportion of cells (<3%) separately that did not overlap with little variability in cell lines and PMCs. All surface markers were co-expressed in ALDH1A1+ cells without preference for one combination. The cell cycle analysis of ALDH1A1+ cells alone revealed that majority of them reside in G0/G1 phase of cell cycle. Further separation of G0 and G1 phases showed that ALDH1A1+ cells reside in G1 phase of the cell cycle. Xenograft assays showed that the combinations of ALDH1A1 + cells co-expressing CD9, CD24 or EPHA1 were more tumorigenic and aggressive with respect to ALDH1A1-cells. These data suggest that a combined approach could be more useful in identifying CSCs in HGSOC.

Oncogenes in high grade serous adenocarcinoma of the ovary.

High grade serous ovarian cancer is characterized by relatively few mutations occurring at low frequency, except in TP53. However other genetic aberrations such as copy number variation alter numerous oncogenes and tumor suppressor genes. Oncogenes are positive regulators of tumorigenesis and play a critical role in cancer cell growth, proliferation, and survival. Accumulating evidence suggests that they are crucial for the development and the progression of high grade serous ovarian carcinoma (HGSOC). Though many oncogenes have been identified, no successful inhibitors targeting these molecules and their associated pathways are available. This review discusses oncogenes that have been identified recently in HGSOC using different screening strategies. All the genes discussed in this review have been functionally characterized both in vitro and in vivo and some of them are able to transform immortalized ovarian surface epithelial and fallopian tube cells upon overexpression. However, it is necessary to delineate the molecular pathways affected by these oncogenes for the development of therapeutic strategies.

Analysis of Human Stem Cell Transcription Factors.

Transcription factors NANOG, OCT4, SOX2, and NESTIN are expressed in both human embryonic stem cells (hESCs) and cancer stem cells and they play a crucial role in maintaining characteristics of stemness such as self-renewal and pluripotency. This article evaluates the expression of variants of the main stem cell-specific transcription factors NANOG and OCT4 critically and accurately with specific primers designed for identifying the most important variants that maintain stemness. We have examined four variants of NANOG along with a processed pseudogene and seven variants of OCT4 in human teratocarcinoma cell lines (NTERA2D1, SuSa, GCT-27, and 833KE), hESCs, and ovarian cancer cells by reverse transcriptase-polymerase chain reaction. In addition, we have examined their expression in NTERA2D1 cells on differentiation with all-trans-retinoic-acid. We show that NANOG1 is expressed in all teratocarcinoma cells and can be distinguished from NANOGP8, which is an expressed pseudogene. NANOG2 was not expressed in any of the cell lines, including ESCs. OCT4A was expressed in all cells, whereas the variant OCT4B-variant 3 was expressed only in NTERA2D1 cells. On differentiation of NTERA2D1 with retinoic acid, only NANOGP8 and OCT4A were expressed. In ovarian cancer cells, only 3/6 expressed NANOG1 and OCT4A. All malignant cells from patients with ovarian cancer (N = 6) expressed NANOG1 and OCT4A. These results demonstrate the necessity to precisely evaluate the expression of stem cell transcription factors when defining stemness.