Pluripotency transcription factors in the pathogenesis of colorectal cancer and implications for prognosis

Identification of a novel prognostic signature composed of 3 cuproptosis-related transcription factors in colon adenocarcinoma

BACKGROUND

Since the mechanism of cuproptosis was recently revealed, many molecules related to this pathway have been widely concerned and exploited to have prognostic potential. However, it is still unknown whether the transcription factors related to cuproptosis could be competent as tumor biomarkers of colon adenocarcinoma (COAD).

OBJECTIVE

To analyze the prognostic potential of cuproptosis-related transcription factors in COAD, and validate the representative molecule.

METHODS

Transcriptome data and patients' clinical parameters were obtained from the TCGA and GEO database. 19 cuproptosis genes were identified through literature consulting. Cuproptosis-related transcription factors were screened by COX regression analyses. Multivariate Cox regression was applied to construct the signature. Prognostic effects were evaluated by Kaplan Meier survival analyses and ROC analyses. KEGG, GO, and ssGSEA analyses were performed for function prediction. 48 COAD tissues were collected for immunohistochemistry stain to observe the expression level and prognostic value of E2F3. qRT-PCR was performed to detect mRNA expression levels, while cell viability assay was applied to detect the response of COAD cells to elesclomol treatment.

RESULTS

A novel signature based on 3 prognostic transcription factors related to cuproptosis was successfully established and verified. Patients in the low-risk group tended to have better overall survival and lower immune phenotype scores than those in the high-risk group. Meanwhile, we also constructed a nomogram based on this signature and predict 10 candidate compounds targeting this signature. As an essential member of this signature, E2F3 was confirmed to be overexpressed in COAD tissues and was associated with poor prognosis of COAD patients. Importantly, CuCl2 and cuproptosis inducer elesclomol treatment could increase the expression of E2F3 in COAD cell while the overexpression of E2F3 significantly enhanced the resistance of COAD cells to elesclomol treatment.

CONCLUSION

Our research has identified a new prognostic biomarker and provides some innovative insights into the diagnosis and therapy of patients with COAD.

The Safe Soluble Compound Dehydroascorbic Acid Inhibits Various Upstream and Downstream Effectors of PI3K and KRAS Signaling Pathways in Undruggable PIK3CA/KRAS-Mutant Colorectal Cancer Stem-Like Cells

Efforts to develop effective drugs targeting PI3K and KRAS signaling pathways in PIK3CA/KRAS-mutant colorectal cancer stem cells (CRCSCs) remain challenging. Finding safe compounds that can easily enter CRCSCs with the ability to target metastasis-driver gene CXCR4 and pluripotency network genes as key upstream and downstream effectors of both PI3K and KRAS signaling pathways may provide promising results. PIK3CA/KRAS-mutant CRCSCs display high expression of glucose transporters (GLUTs) on their cell membrane and a glycolytic phenotype providing an opportunity to deliver antiglycolytic compounds into these cells via the GLUTs. CRC patients with low levels of vitamin C in their plasma show a shorter survival suggesting the ability of this vitamin at the physiologic levels for caspase-3 activation and apoptosis in CRCSCs. Vitamin C in an oxidized form (L-dehydroascorbic acid; L-DHA) with antiglycolytic activity can be taken up into CRC cells via the GLUTs. This may provide selective toxicity on CRCSCs and affect CXCR4 and stemness markers genes expression in these cells. To this end, we treated PIK3CA/KRAS-mutant LS174T cells with high glycolytic activity as an attractive model for CRCSCs with L-DHA equal to the pharmacological levels of vitamin C in human plasma, after which cell numbers, metabolic activity, proliferation-rate, CXCR4 and pluripotency network genes expression, caspase-3 activity with apoptosis were evaluated. 48 h post-treatment with 100- to 1000 µM L-DHA, cell numbers were decreased and measured to be 70-47% control. L-DHA with selective toxicity on LS174T cells diminished metabolic activity and cell proliferation-rate to 1.4-0.8 (Control OD = 1.5) and 92-54.5% respectively with no toxicity on PBMCs. L-DHA decreased CXCR4, Bmi-1, Sox-2 and Oct-4 expression to 45%, 85%, 45% and 48% control respectively followed by caspase-3 reactivation by 2.5 to 4.9-fold increases and induction of apoptosis ranging from 0.5% to 58.3% for 100- to 1000 µM L-DHA. According to our data, CRC stem-like cells were highly sensitive to L-DHA in in-vitro. L-DHA selectively targeted LS174T cells and successfully reactivated caspase-3 and apoptosis in these cells. CXCR4, stemness marker genes and metabolic activity appear to be promising targets of L-DHA. Our results may provide a new therapeutic approach to target selectively GLUT-overexpressing PIK3CA/KRAS-mutant CRCSCs using L-DHA with no toxicity on normal cells.

The response of PIK3CA/KRAS-mutant colorectal cancer stem-like cells to RGD-peptide FraC produced by the strawberry anemone: A promising water-soluble peptide-based inhibitor of metastasis-driver gene CXCR4, stem cell regulatory genes and self-renewal

Colorectal cancer (CRC) is a stem cell-based disease. PIK3CA/KRAS-mutant CRC stem cells (CRCSCs) display high self-renewal, metastatic properties, high activity of PI3K and KRAS signaling pathways with chemoresistant phenotypes. Recently, RGD peptide (containing Arg-Gly-Asp motif)-based therapy of solid tumor cells has attracted much attention. However, little is known whether this method can target self-renewal capacity, key effectors of PI3K and KRAS signaling pathways such as metastasis-driver gene CXCR4 and stem cell regulatory genes with caspase-3 reactivation in CRCSCs overexpressing RGD-dependent integrins. The sea anemone Actinia fragacea produces a water-soluble RGD-peptide fragacea toxin C (FraC) suggesting the possible activity of FraC against PIK3CA/KRAS-mutant CRCSCs. Recombinant FraC was expressed via pET-28a(+)-FraC in E. coli and purified through affinity chromatography followed by performing SDS-PAGE and hemolytic activity assay. Next, PIK3CA/KRAS-mutant HCT-116 cells that serve as an attractive model for CRCSCs were treated with FraC. Thereafter, cell numbers, viability, proliferation, LDH activity, cytotoxicity index, CXCR4 and pluripotency network genes expression, self-renewal capacity, caspase-3 activity with apoptosis were evaluated. Caspase-1, -2, -3,…, -9 sequences were analyzed for RGD-binding motifs. FraC sequence and structure were also evaluated by bioinformatics software. FraC altered cellular morphology to round shapes and disrupted cell connections. 48 h post-treatment with 0.056- to 7.2 μM FraC resulted in 12 %-99 % and 8 %-97.6 % decreases in cell numbers and viabilities respectively and increased LDH activity by 0.2 %-66.7 % in a dose-dependent manner. The results of the cytotoxicity index showed that FraC induces significant toxicity on HCT-116 cells compared to PBMCs and Huvec cells. FraC dramatically decreased the expression of CXCR4 and pluripotency network genes Bmi-1, Sox-2, Oct-4 and Nanog followed by remarkable decreases in self-renewal capacity ranged from 91- to 0 colonies per well for 0.056- to 3.6 μM FraC after 2 weeks. Caspase-3 was found to contain an RGD-binding motif and its activity increased with increasing FraC concentrations followed by apoptosis induction. Potential RGD-binding motifs for FraC were also found in caspase-1, -7, -8 and -9. Unique advantages of FraC peptide, such as low molecular weight, water solubility, high sensitivity of CRC stem-like cells with more selective toxicity to this compound, targeting tumor cell membrane and self-renewal capacity along with the modulation of CXCR4 and stem cell regulatory genes as upstream and downstream effectors of undruggable PI3K and KRAS signaling pathways may open up avenues for FraC peptide-based therapy of PIK3CA/KRAS-mutant CRCSCs with lower toxicity on healthy cells.

miR-296-5p suppresses stem cell potency of hepatocellular carcinoma cells via regulating Brg1/Sall4 axis

Epithelial-mesenchymal transition (EMT), a pivotal event during cancer progression such as relapse and metastasis, is positively correlated with the stemness potency of tumor cells. Our previous study showed that miR-296-5p attenuated EMT program of hepatocellular carcinoma cells (HCC) through NRG1/ERBB2/ERBB3 signaling. In the present study, we uncovered that miR-296-5p was able to inhibit the stemness potency of HCC by decreasing the number and size of tumorspheres, downregulating the expression of CSC biomarkers and hampering the ability of tumorigenesis in NOD/SCID mice. Brahma-related gene-1 (Brg1), as the target protein of miR-296-5p detected by bioinformatics methods, activates a series of downstream cascades through directly binding to Sall4 promoter and enhancing Sall4 transcription. Importantly, the higher expressions of Brg1 and Sall4 in tumor tissues of HCC patients suggest poorer prognoses after surgical extraction. In conclusion, miR-296-5p exerts an inhibitory effect on stemness potency of HCC cells via Brg1/Sall4 axis.

Modulating Pluripotency Network Genes with Omega-3 DHA is followed by Caspase- 3 Activation and Apoptosis in DNA Mismatch Repair-Deficient/KRAS-Mutant Colorectal Cancer Stem-Like Cells

BACKGROUND

Targeting DNA mismatch repair-deficient/KRAS-mutant Colorectal Cancer Stem Cells (CRCSCs) with chemical compounds remains challenging. Modulating stemness factors Bmi-1, Sox-2, Oct-4 and Nanog in CRCSCs which are direct downstream targets of carcinogenesis pathways may lead to the reactivation of caspase-3 and apoptosis in these cells. Omega-3 DHA modulates different signaling pathways involved in carcinogenesis. However, little is known, whether in vitro concentrations of DHA equal to human plasma levels are able to modulate pluripotency genes expression, caspase-3 reactivation and apoptosis in DNA mismatch repair-deficient/KRAS-mutant CRC stem-like cells.

METHODS

DNA mismatch repair-deficient/KRAS-mutant CRC stem-like cells (LS174T cells) were treated with DHA, after which, cell number and proliferation-rate, Bmi-1, Sox-2, Nanog and Oct-4 expression, caspase-3 activation and apoptosis were evaluated with different cellular and molecular techniques.

RESULTS

DHA changed the morphology of cells to apoptotic forms and disrupted cell connections. After 48h treatment with 50- to 200μM DHA, cell numbers and proliferation-rates were measured to be 86%-35% and 93.6%-45.7% respectively. Treatment with 200 μM DHA dramatically decreased the expression of Bmi-1, Sox- 2, Oct-4 and Nanog by 69%, 70%, 97.5% and 53% respectively. Concurrently, DHA induced caspase-3 activation by 1.8-4.7-fold increases compared to untreated cells. An increase in the number of apoptotic cells ranging from 9.3%-38.4% was also observed with increasing DHA concentrations.

CONCLUSIONS

DHA decreases the high expression level of pluripotency network genes suggesting Bmi-1, Sox-2, Oct-4 and Nanog as promising molecular targets of DHA. DHA reactivates caspase-3 and apoptosis in DNA mismatch repair-deficient/KRAS-mutant CRC stem-like cells, representing the high potential of this safe compound for therapeutic application in CRC.

Salinomycin exerts anti-colorectal cancer activity by targeting the β-catenin/T-cell factor complex

BACKGROUND AND PURPOSE

Salinomycin is a well-known inhibitor of human cancer stem cells (CSCs). However, the molecular mechanism(s) by which salinomycin targets colorectal CSCs is poorly understood. Here, we have investigated underlying antitumour mechanisms of salinomycin in colorectal cancer cells and three tumour models.

EXPERIMENTAL APPROACH

The inhibitory effect of salinomycin on the Wnt/β-catenin pathway was analysed with the SuperTopFlash reporter system. The mRNA expression of Wnt target genes was evaluated with real-time PCR. Effects of salinomycin on β-catenin/TCF4E interaction were examined using co-immunoprecipitation and an in vitro GST pull-down assay. Cell proliferation was determined by BrdU incorporation and soft agar colony formation assay. The stemness of the cells was assessed by sphere formation assay. Antitumour effects of salinomycin on colorectal cancers was evaluated with colorectal CSC xenografts, APCmin/+ transgenic mice, and patient-derived colorectal tumour xenografts.

KEY RESULTS

Salinomycin blocked β-catenin/TCF4E complex formation in colorectal cancer cells and in an in vitro GST pull-down assay, thus decreasing expression of Wnt target genes. Salinomycin also suppressed the transcriptional activity mediated by β-catenin/LEF1 or β-catenin/TCF4E complex and exhibited an inhibitory effect on the sphere formation, proliferation, and anchorage-independent growth of colorectal cancer cells. In colorectal tumour xenografts and APCmin/+ transgenic mice, administration of salinomycin significantly reduced tumour growth and the expression of CSC-related Wnt target genes including LGR5.

CONCLUSIONS AND IMPLICATIONS

Our study suggested that salinomycin could suppress the growth of colorectal cancer by disrupting the β-catenin/TCF complex and thus may be a promising agent for colorectal cancer treatment.

The pluripotency network in colorectal cancer pathogenesis and prognosis: an update

Stemness characteristics are defining properties of cancer initiating cells and are associated with the ability to metastasize and survive in hostile environments. Establishment of the stem cell network depends on the action of a set of core transcription factors that work in concert with other ancillary proteins that are also important during embryonic development. New data consolidate the role of core pluripotency transcription factors OCT4, SOX2 and NANOG as adverse prognostic factors in colorectal cancer. mRNA-binding proteins LIN28 and Musashi, that are associated with stemness, and epigenetic modifiers such as de-acetylase SIRT1 may also have prognostic value in colorectal cancer. This paper provides an update of the stem cell factors in the pathogenesis and prognosis of colorectal cancer.

Expression and function of immune ligand-receptor pairs in NK cells and cancer stem cells: therapeutic implications

BACKGROUND

The interplay between the immune system and cancer cells has come to the forefront of cancer therapeutics, with novel immune blockade inhibitors being approved for the treatment of an increasing list of cancers. However, the majority of cancer patients still display or develop resistance to these promising drugs. It is possible that cancer stem cells (CSCs) are contributing to this therapeutic resistance. Although CSCs usually represent a small percentage of the total number of cancer cells, they are endowed with the ability of self-renewal and to produce differentiated progeny. Additionally, they have shown the capacity to establish tumors after transplantation to animals, even in small numbers. CSCs have also been found to be resistant to various anti-cancer therapies, including chemotherapy, radiation therapy and, more recently, immunotherapy. This is true despite the sensitivity of CSCs to lysis in vitro by natural killer (NK) cells, the main effector cells of the innate immune system. In this paper the expression of ligands specific for NK cells on CSCs, the intracellular network responsible for the expression of the NK cytotoxicity receptors, and the status of activation of NK cells in the tumor micro-environment are reviewed. The aim of this review is to highlight potential strategies for overcoming CSC immune resistance, thereby enhancing the efficacy of current and future anti-cancer therapies.

THERAPEUTIC IMPLICATIONS

NK cell activation in the tumor micro-environment through drugs neutralizing inhibitory immune receptors, and combined with other drugs harnessing the potential of the adaptive immune system, could be the most effective approach for attacking both stem cell and non-stem cell cancer populations.

Characterization of Cancer Stem Cells in Colon Adenocarcinoma Metastasis to the Liver

Background

Fifty percent of colorectal cancer (CRC) patients develop liver metastasis. This study identified and characterized cancer stem cells (CSCs) within colon adenocarcinoma metastasis to the liver (CAML).

Methods

3,3-Diaminobenzidine immunohistochemical (IHC) staining was performed on nine CAML samples for embryonic stem cell (ESC) markers OCT4, SOX2, NANOG, c-Myc, and KLF4. Immunofluorescence (IF) IHC staining was performed to investigate coexpression of two markers. NanoString mRNA expression analysis and colorimetric in situ hybridization (CISH) were performed on four snap-frozen CAML tissue samples for transcript expression of these ESC markers. Cells stained positively and negatively for each marker by IHC and CISH staining were counted and analyzed.

Results

3,3-Diaminobenzidine IHC staining, and NanoString and CISH mRNA analyses demonstrated the expression of OCT4, SOX2, NANOG, c-Myc, and KLF4 within in all nine CAML samples, except for SOX2 which was below detectable levels on NanoString mRNA analysis. IF IHC staining showed the presence of a SOX2⁺/NANOG⁺/KLF4⁺/c-Myc⁺/OCT⁻ CSC subpopulation within the tumor nests, and a SOX2⁺/NANOG⁺/KLF4⁺/c-Myc⁺/OCT4⁻ CSC subpopulation and a SOX2⁺/NANOG⁺/KLF4⁺/c-Myc⁺/OCT4⁺ CSC subpopulation within the peritumoral stroma.

Conclusion

The novel finding of three CSC subpopulations within CAML provides insights into the biology of CRC.

Proteasome expression and activity in cancer and cancer stem cells

Proteasome is a multi-protein organelle that participates in cellular proteostasis by destroying damaged or short-lived proteins in an organized manner guided by the ubiquitination signal. By being in a central place in the cellular protein complement homeostasis, proteasome is involved in virtually all cell processes including decisions on cell survival or death, cell cycle, and differentiation. These processes are important also in cancer, and thus, the proteasome is an important regulator of carcinogenesis. Cancers include a variety of cells which, according to the cancer stem cell theory, descend from a small percentage of cancer stem cells, alternatively termed tumor-initiating cells. These cells constitute the subsets that have the ability to propagate the whole variety of cancer and repopulate tumors after cytostatic therapies. Proteasome plays a role in cellular processes in cancer stem cells, but it has been found to have a decreased function in them compared to the rest of cancer cells. This article will discuss the transcriptional regulation of proteasome sub-unit proteins in cancer and in particular cancer stem cells and the relationship of the proteasome with the pluripotency that is the defining characteristic of stem cells. Therapeutic opportunities that present from the understanding of the proteasome role will also be discussed.

Comparison of gene expression of SOX2 and OCT4 in normal tissue, polyps, and colon adenocarcinoma using immunohistochemical staining

BACKGROUND

Cancer stem cells have been isolated and characterized in all common cancers. SOX2 and OCT4 are important genes to enhance the self-renewal ability as activate stem cells and inhibit the genes that start differentiation and thus maintain the self-renewal ability of stem cells. Also, the aim of this study is "Comparison of gene expression of SOX2 and OCT4 in normal tissue, polyps, and colon adenocarcinoma using immunohistochemical staining."

MATERIALS AND METHODS

This cross-sectional study conducted on 20 patients so that for each patient, a sample of healthy tissue, dysplastic polyp tissue, and colon adenocarcinoma were provided as microscopic sections and staining on each tissue was performed through immunohistochemistry method by markers OCT4 and SOX2. The collected data were interred into SPSS version 18.0, (SPSS Inc., Chicago, IL, USA) software and the level of significance were considered as <0.05.

RESULTS

The study sample consisted of 20 patients including 11 men (55%) and 9 women (45%) with a mean age of 55.6 ± 9.88 years. There was no association between Oct4 and colorectal cancer (CRC) patients (P > 0.05), but there was a significant correlation between Sox2 expression and CRC (P < 0.05). Patients in many aspects such as race, type of polyp, presence of lymph node, grade and intensity of Sox2 in different types of patients' tissues (P < 0.05).

CONCLUSION

Regarding our findings, the expression of Sox2 would be a liable marker for evaluating of cancer progression and could be a treatment target of CRC cells.