Table 3.

Evidence for pluripotency factor involvement in cancer

CancerPluripotency factor involved (context of study)Description of studyReference
Breast cancerOCT4 and NANOG mRNA expression (primary tumors and cell lines)Quantitative RT-PCR on a stage 3 breast carcinoma sample showed increased NANOG and OCT4 expression compared with nondetectable levels in normal breast tissue.157
Immunohistochemistry revealed NANOG protein in breast carcinoma sample but not in normal breast tissue.
The MCF7 breast carcinoma cell line was found to express OCT4 and NANOG.
Breast cancer⇑ SOX2 protein levels (primary tumors)Immunohistochemistry was used to analyze SOX2 protein levels in a cohort of 95 patients with sporadic, postmenopausal, early breast cancer.104
Four expression scores were defined to distinguish SOX2-negative and -positive samples (score 0 = no SOX2-positive cells; score 1 = >0 and <10% SOX2-positive cells; score 2 = ≥10 and <50% SOX2-positive cells; score 3 = ≥50% SOX2-positive cells.
SOX2 was expressed in 24/86 invasive breast carcinoma samples and 4/9 DCIS samples. Tumors expressing ≥50% SOX2-positive cells were significantly larger and significantly associated with lymph-node metastases.
FISH of selected samples revealed that increased SOX2 protein levels were not due to SOX2 gene amplification, suggesting that the aberrant gene expression is driven by other mechanisms.
Breast cancerNANOG, OCT4, SOX2 mRNA expression (mammospheres) ⇑ NANOG and SOX2 mRNA expression (primary tumors)Investigated the effects of estrogen on the stem/progenitor cell population in normal breast and breast cancer tissues. NANOG, OCT4, and SOX2 expression was used to monitor the differentiation status of breast stem cells in the presence of either estrogen or tamoxifen. Expression levels of NANOG, OCT4, and SOX2 were determined in freshly isolated organoids from reduction mammoplasties, breast epithelial cells derived from the organoids and grown as adherent cells in the presence of serum, and mammospheres originating from single breast epithelial cells.158
Compared with freshly isolated organoids, NANOG, OCT4, and SOX2 mRNA expression was lower in differentiated (adherent) cells and significantly higher in the mammospheres. Estrogen treatment significantly reduced NANOG, OCT4, and SOX2 expression in mammospheres. Furthermore, estrogen treatment reduced the percentage of stem/progenitor cells in mammospheres, whereas tamoxifen increased the percentage.
NANOG and SOX2 mRNA expression levels were determined in breast tumor samples and compared with levels in normal adjacent tissue. Increased expression of NANOG and SOX2 was seen in the breast tumor samples.
Breast cancerPossession of embryonic stem cell expression signature correlateswith aggressive tumor behaviorGene set expression analysis methods were used to assess whetherthe expression signatures and regulatory networks that define human embryonic stem-cell identity are also active in human tumors.105
Thirteen partially overlapping gene sets were compiled that represent the core expression signature of embryonic stem cells and reflect the activity of the regulatory pathways associated with their identity. These gene sets fall into 1 of 4 groups: embryonic stem-expressed genes; Nanog, Oct4, and Sox2 (NOS) targets; Polycomb targets; and Myc targets.
Expression profiles from 6 published breast cancer studies, comprising a total of 1,211 tumors, were collected and analyzed.
Grade 3 tumors showed an enrichment pattern resembling that observed in embryonic stem cells, including underexpression of Polycomb target gene sets and overexpression of embryonic stem cell–expressed sets, Myc-target gene sets, and some of the NOS-target gene sets.
ER-positive tumors showed an embryonic stem cell–like enrichment pattern compared with ER-negative tumors.
Tumors of larger size at the time of diagnosis were more likely to possess the embryonic stem-cell signature compared with smaller tumors, even within a given grade.
Colorectal cancer⇑ NANOG protein levels (primary tumors)Western blot was used to analyze NANOG levels in 175 fresh colorectal cancer samples.106
NANOG protein levels were higher in most of the colorectal cancer samples compared with paired normal mucosal tissue.
Immunohistochemistry was used to analyze NANOG localization in paraffin-embedded colorectal cancer tissue.
NANOG was mainly localized to the cytoplasm of cancer cells. Nuclear accumulation of NANOG was only observed in a small fraction of cancer cells. NANOG expression positively correlated with lymph node status and Dukes classification of patients. High NANOG expression correlated with a shorter survival or recurrence free survival.
Colorectal cancer cells were studied for the effects of NANOG overexpression on proliferation, invasion, and motility. Overexpression resulted in increased proliferation, colony formation, and invasive ability.
Rectal cancerCD133, OCT4, SOX2 mRNA expression associated with distant recurrences (primary tumors)CD133, OCT4, and SOX2 levels were analyzed before and after chemoradiotherapy to clarify the association between expression of stem-cell markers and chemoradiotherapy resistance in rectal cancer.108
Thirty-three patients.
Quantitative RT-PCR on pre-chemoradiotherapy endoscopic tumor samples revealed a positive correlation between OCT4 and SOX2 but not between CD133 and OCT4 or SOX2.
Analysis of formalin-fixed, paraffin-embedded, post-chemoradiotherapy residual cancer samples showed significant positive correlations among CD133, OCT4, and SOX2.
Patients who developed distant recurrences had significantly higher post-chemoradiotherapy levels of CD133, OCT4, and SOX2 compared with patients without recurrences.
Of the 33 patients, 28 received a low dose of radiation and 5 received a high dose of radiation. Post-chemoradiotherapy OCT4 levels were significantly higher in the high-dose radiation group compared with the low-dose radiation group. CD133 and SOX2 levels were also higher, but this difference did not reach statistical significance.
Immunohistochemistry was used to confirm protein expression in residual cancer cells after chemoradiotherapy. CD133 was observed diffusely in the cytoplasm of residual cancer cells and at the apical/endoluminal surface of residual cancer cells with the formation of lumina and ducts. OCT4 and SOX2 were observed diffusely in the cytoplasm of residual cancer cells.
Prostate cancer⇑ OCT4 and SOX2 protein expression (primary tumors)OCT4, SOX2, NANOG, c-MYC, and Klf4 mRNA levels were increased in 28/55 prostate cancer samples. All possible combinations of transcription factors showed that significance was achieved only between OCT4 and SOX2, suggesting a possible functional link between OCT4 and SOX2 in prostate cancer cases.107
Immunohistochemistry was used to evaluate OCT4 and SOX2 levels in normal prostate, benign prostate hyperplasia, and prostate cancer samples. Staining was categorized into 4 groups: (i) negative; (ii) low, <5%; (iii) intermediate, 5–25%; and (iv) high, 26–50%. The numbers of OCT4- or SOX2-expressing cells were significantly lower in normal prostate and benign prostate hyperplasia samples than in prostate tumor tissues. In prostate tumor samples, an increasing number of OCT4- and SOX2-expressing cells were evident with increasing Gleason score.
Bladder cancerOCT4 mRNA expression (primary tumors)Investigated OCT4 expression in bladder cancer.159
Semiquantitative RT-PCR showed OCT4 expression in almost all (96%) of the examined bladder cancer samples. Expression was also detected in 23% of nontumor marginal tissues from thesame patients and 33% of nontumor bladder tissues obtained from patients with no obvious signs of bladder cancer.
Densitometric evaluation of the semiquantitative RT-PCR results revealed that the intensity of OCT4 expression was significantly higher in neoplastic tissues compared with nonneoplastic samples.
Protein levels were also examined by immunohistochemistry. OCT4 was primarily localized to the nuclei of tumor cells, with no immunoreactivity in normal cells adjacent to the tumors.