Radiobiological effects of cancer stem cell-targeting therapy in a head and neck cancer model
0
Citation
0
Reference
10
Related Paper
Keywords:
Radioresistance
Differentiation Therapy
Side population
The presence of cancer stem cells (CSCs) has major implications in the choice of cancer treatment strategy and is responsible for tumor relapse. CSCs have been isolated and characterized in several types of cancer; however, studies concerning the CSCs from nasopharyngeal carcinoma (NPC) are limited. Thus, the present study was designed to isolate and characterize the cancer stem-like side population (SP) cells from NPC samples. The fluorescence-activated cell sorting (FACS)-based Hoechst 33342 dye exclusion technique identified that 3.9% of cells from NPC samples were cancer stem-like SP cells. Upon treatment with verapamil (ABC transporter inhibitor), the percentage of SP cells was significantly reduced to 0.7%, which confirms that the ABC transporter protein exhibits a significant role in drug exclusion. Fluorescence microscopy analysis revealed that the FACS purified SP cells showed increased expression of ABCG2 (ATP transporter protein), Oct-4 and CD44 (stem cell surface protein). Furthermore, these SP cells exhibited increased mRNA expression of ABCG2 and anti-apoptotic factor Bmi-1, which contribute to multi-drug resistance and increased cell survival rate. Notably, the Wnt/β-catenin signaling pathways are altered in SP cells. In addition, using reverse transcription‑quantitative polymerase chain reaction analysis it was observed that the cells exhibited increased expression of DKK1 and AXIN2. In conclusion, data from the present study clearly demonstrated that the presence of cancer stem-like SP cells from NPC may be responsible for chemotherapeutic drug resistance, tumor recurrence and invasion.
Side population
Abcg2
Cell Sorting
Stem cell marker
Cite
Citations (15)
CSCs (cancer stem cells) are a small subset of cells within a tumour that possesses the characteristics of stem cells and are considered to be responsible for resistance to chemoradiation. Identification of CSCs through stem cell characteristics might have relevant clinical implications. In this study, SP (side population) cells were sorted from a human ovarian cancer cell line by FACS to determine whether cancer stem cell-like SP cells were present. A very small fraction of SP cells (2.6%) was detected in A2780 cells. SP cells possessed the following characteristics: highly proliferative activity, marked ability for self-renewal in soft agar and culture medium, high expression of ABCG2, drug resistance to vinblastine in vitro, and strong tumourigenic potential in Balb/c nude mice. It is concluded that there exists in the A2780 cell line a small number of SP cells with high expression of ABCG2. The cells have the characteristics of cancer stem-like cells, and identification and cloning of such human SP cells can help in improving therapeutic approaches to ovarian cancer in patients.
Side population
Abcg2
Stem cell marker
Cite
Citations (53)
Abstract Recently, several human cancers including leukemia and breast and brain tumors were found to contain stem-like cancer cells called cancer stem cells (CSC). Most of these CSCs were identified using markers that identify putative normal stem cells. In some cases, stem-like cancer cells were identified using the flow cytometry-based side population technique. In this study, we first show that ∼30% of cultured human cancer cells and xenograft tumors examined (∼30 in total) possess a detectable side population. Purified side population cells from two cell lines (U373 glioma and MCF7 breast cancer) and a xenograft prostate tumor (LAPC-9) are more tumorigenic than the corresponding non–side population cells. These side population cells also possess some intrinsic stem cell properties as they generate non–side population cells in vivo, can be further transplanted, and preferentially express some “stemness” genes, including Notch-1 and β-catenin. Because the side population phenotype is mainly mediated by ABCG2, an ATP-binding cassette half-transporter associated with multidrug resistance, we subsequently studied ABCG2+ and ABCG2− cancer cells with respect to their tumorigenicity in vivo. Although side population cells show increased ABCG2 mRNA expression relative to the non–side population cells and all cancer cells and xenograft tumors examined express ABCG2 in a small fraction (0.5-3%) of the cells, highly purified ABCG2+ cancer cells, surprisingly, have very similar tumorigenicity to the ABCG2− cancer cells. Mechanistic studies indicate that ABCG2 expression is associated with proliferation and ABCG2+ cancer cells can generate ABCG2− cells. However, ABCG2− cancer cells can also generate ABCG2+ cells. Furthermore, the ABCG2− cancer cells form more and larger clones in the long-term clonal analyses and the ABCG2− population preferentially expresses several “stemness” genes. Taken together, our results suggest that (a) the side population is enriched with tumorigenic stem-like cancer cells, (b) ABCG2 expression identifies mainly fast-cycling tumor progenitors, and (c) the ABCG2− population contains primitive stem-like cancer cells.
Side population
Abcg2
Cite
Citations (907)
Radioresistance
Cite
Citations (2)
Lung cancer is among the most lethal malignancies with a high metastasis and recurrence rate. Recent studies indicate that tumors contain a subset of stem-like cancer cells that possess certain stem cell properties. Herein, we used Hoechst 33342 dye efflux assay and flow cytometry to isolate and characterize the side population (SP) cells from human lung cancer cell line NCI-H460 (H460). We show that the H460 SP cells harbor stem-like cells as they can readily form anchorage-independent floating spheres, possess great proliferative potential, and exhibit enhanced tumorigenicity. Importantly, the H460 SP cells were able to self-renew both in vitro and in vivo. Finally, we show that the H460 SP cells preferentially express ABCG2 as well as SMO, a critical mediator of the Hedgehog (HH) signaling, which seems to play an important role in H460 lung cancer cells as its blockage using Cyclopamine greatly inhibits cell-cycle progression. Collectively, our results lend further support to the existence of lung cancer stem cells and also implicate HH signaling in regulating large-cell lung cancer (stem) cells.
Side population
Cyclopamine
Stem cell marker
Cite
Citations (80)
The cancer stem cell (CSC) theory concludes that a subpopulation of cancer cells, the cancer stem cells, can self-renew and are responsible for tumor growth. Previous studies have identified cells able to efflux Hoechst 33342 dye as the side population (SP). SP cells and CSCs share many characteristics, suggesting the SP isolated from malignant tumors contains CSCs.Experimental Study.The SP was isolated from a head and neck cancer cell line and analyzed for CSC-like characteristics.The SP demonstrated the ability to reproduce both SP and non-side population (NSP) cells from as few as one cell. The SP had lower expression of active β-catenin and more resistance to 5-fluorouracil; the SP also demonstrated greater expression of Bmi-1 (4.3-fold) and ABCG2 (1.4-fold). SP cells were able to produce tumors in an animal model, whereas NSP were not. SPs were identified in two primary human tumors.This work adds to the evidence that the SP in head and neck cancer represents cells with CSC properties and provides a method by which CSCs can be isolated and studied.
Side population
Abcg2
Cite
Citations (71)
Several studies have demonstrated that the isolated side population (SP) cells from solid tumors exhibit cancer stem cell‑like properties, and are responsible for drug resistance during chemotherapy and tumor recurrence. In the current study, cancer stem cell‑like SP cells were isolated in the MDU‑22 breast cancer cell line using the Hoechst‑33342 dye exclusion technique. It was observed that SP cells accounted for 3.8% of cells in the MDU‑22 cell line, which was reduced to 0.6% in the presence of verapamil, an inhibitor of the ABC transporter. The sorted SP cells showed an elevated expression of stem cell markers, including ABCG2, OCT‑4 and EpCAM. Furthermore, it was demonstrated that the isolated SP cells undergo rapid proliferation and have a high survival rate. These results indicate that the coexpression of adenosine triphosphatase binding cassette transporters and stem cell surface markers in SP cells may contribute to chemoresistance, tumor recurrence, metastasis and invasion. Therefore, the isolation and characterization of SP cells may provide novel insights for the development of alternative therapeutic agents to target cancer stem cells.
Side population
Abcg2
Stem cell marker
Cite
Citations (41)
Radioresistance remains a major obstacle for the radiotherapy treatment of cancer. Previous studies have demonstrated that the radioresistance of cancer is due to the existence of intrinsic cancer stem cells (CSCs), which represent a small, but radioresistant cell subpopulation that exist in heterogeneous tumors. By contrast, non-stem cancer cells are considered to be radiosensitive and thus, easy to kill. However, recent studies have revealed that under conditions of radiation-induced stress, theoretically radiosensitive non-stem cancer cells may undergo dedifferentiation subsequently obtaining the phenotypes and functions of CSCs, including high resistance to radiotherapy, which indicates that radiation may directly result in the generation of novel CSCs from non-stem cancer cells. These findings suggest that in addition to intrinsic CSCs, non-stem cancer cells may also contribute to the relapse and metastasis of cancer following transformation into CSCs. This review aims to investigate the radiation-induced generation of CSCs, its association with epithelial-mesenchymal transition and its significance with regard to the radioresistance of cancer.
Radioresistance
Cite
Citations (89)
The cancer stem cell hypothesis implicates that tumor cell population is heterogeneous with relatively well-differentiated cells and poorly-differentiated cells. Only the small population of tumourigenic poorly-differentiated CSCs can escape the normal limits of self-renewal and has the ability to proliferate and maintain the malignant growth of the tumor.
One characteristic of stem cell is that the ability to exclude DNA dyes, such as Hoechst 33342 via the over-expression of ATP-binding cassette transporters (ABC transporters) on the cell membrane. It makes the detecting of the stem cell possible. After the Hoechst 33342 staining, stem cells extrude this dye and show a typical profile of low fluorescence in Hoechst red versus Hoechst blue bivariate dot plots. These low Hoechst 33342 stained cells are named as side population (SP) cells. This characteristic has enabled purification and characterization of CSCs when carried out alone or in combination with stem cell surface markers.
The CSC hypothesis could have a fundamental influence on cancer therapy. CSCs have shown significant substantial resistance to conventional chemotherapy in contrast to the differentiated cancer cells. It is essential to design a complete therapy strategy first to reduce or minimize proliferating cell mass and then to differentiate or eliminate CSCs, so that the relapses of metastatic cancers could be prevented.
This work aimed at investigating if Hedgehog pathway inhibitor GDC-0449 is effective in the lung cancer cell lines HCC (adeno-carcinoma) and H1339 (small cell lung carcinoma) and also the cisplatin resistant lung cancer cells, and if possible effects of GDC-0449 are mediated via SPs. Furthermore, the effect of GDC-0449 on the calcium homeostasis was also investigated.
GDC-0449 showed dose-dependent inhibitory effects on cell growth in both HCC and H1339 cells. The combination of GDC-0449 and cisplatin gave an additional inhibitory effect. GDC- 0449 could also inhibit the cell growth in cisplatin resistant HCC and H1339 cells.
SP cells as cancer stem-cell-like cells could be found in HCC and H1339 cells. Only the SP cells showed the repopulation ability but not the non-SP cells. GDC-0449 could inhibit the SP cell fraction in both HCC and H1339 cells. So the inhibitory effect of GDC-0449 on cell growth may be mediated via SP.
GDC-0449 affected the expression of the Hh pathway components in both HCC and H1339 cells. In HCC cells, GDC-0449 inhibited the activity of the Hh pathway and the down- regulation of Shh, Patched and Gli-1 could be shown. In H1339 cells, GDC-0449 could also inhibit the pathway activity and decrease the expression of Gli-1 in an autocrine pattern due to the over-expression of Shh. The inhibition of Hh pathway increased the expression of Bmi-1 to compensate the loss of Hh pathway function. The Hh pathway activity could be detected only in SP cells from HCC and H1339 cells.
The application of GDC-0449 on HCC and H1339 naive and cisplatin resistant cells increased [Ca2+]c by decreasing [Ca2+]ER. GDC-0449 induced Ca2+ release from ER into cytoplasm in HCC and H1339 naive and cisplatin resistant cells. The Ca2+ overload could lead to apoptosis, which was related to the cell growth inhibitory effect of GDC-0449 in lung cancer cells. The expression of SERCA and IP3R was not detectably influenced by GDC-0449. The effect of GDC-0449 on lung cancer cell Ca2+ -regulating machinery was not via the alternation of the expression of ER Ca2+ regulating channels.
Side population
Cite
Citations (0)
Side population
Abcg2
Tumor initiation
Stem cell marker
Cite
Citations (20)