Lack of P-Glycoprotein Expression by Low-Dose Fractionated Radiation Results from Loss of Nuclear Factor-κB and NF-Y Activation in Oral Carcinoma Cells

Chemopotentiating effects of low-dose fractionated radiation on cisplatin and paclitaxel in cervix cancer cell lines and normal fibroblasts from patients with cervix cancer

The aim of the present study was to compare the effects (assessed by clonogenic survival and γH2AX foci assays) of low-dose fractionated radiation LDFR (4 × 0.125 Gy, 4 × 0.25 Gy and 4 × 0.5 Gy) versus single radiation doses (0.5 Gy, 1 Gy and 2 Gy) on cisplatin and paclitaxel in HRS-negative cervix cancer cell lines SiHa and CaSki to see if the effects of LDFR can emerge in cells that not present low-dose hyper-radiosensitivity (HRS) phenomenon. Additionally, we report the effects in normal fibroblasts (HRS-negative and HRS-positive) from two patients with cervix cancer to see if the chemopotentiating effects of LDFR also apply to normal cells. LDFR (4 × 0.125 Gy, 4 × 0.25 Gy and 4 × 0.5 Gy) as well as single doses (0.5 Gy, 1 Gy and 2 Gy) enhanced cytotoxicity of cisplatin and paclitaxel in all the cell lines. Cisplatin-potentiating effects were maximum with LDFR 4 × 0.5 Gy, and were two-fold greater than those with a single dose of 2 Gy in SiHa, CaSki and HFIB2 cells. Paclitaxel-enhancing effects were also maximum with LDFR 4 × 0.5 Gy, however only in HRS-positive HFIB2 fibroblasts were significantly greater than those with a single dose of 2 Gy. The results demonstrate that LDFR may enhance the effects of cisplatin and paclitaxel in SiHa and CaSki cells, although they lack HRS phenomenon, and show that the magnitude of the potentiating effects of LDFR depends on cytostatic type and the size of low doses. In normal fibroblasts the chemopotentiating effects of LDFR seem to depend on HRS status. In conclusion, the unique enhancing effects of LDFR on cisplatin in cervical cancer cell lines, even when HRS negative, suggest that all patients with cervical cancer may benefit from the addition of LDFR to adjuvant cisplatin-based chemotherapy.

NF-YA promotes the cell proliferation and tumorigenic properties by transcriptional activation of SOX2 in cervical cancer

NF‐YA is considered as a crucial regulator for the maintenance of cancer stem cell (CSC) and involved in various types of malignant tumours. However, the exact function and molecular mechanisms of NF‐YA in the progression of cervical cancer remains poorly understood. Here, the expression of NF‐YA detected by immunohistochemistry was gradually increased from normal cervical tissues, to the high‐grade squamous intraepithelial lesions, and then to cervical cancer tissues. NF‐YA promoted the cell proliferation and tumorigenic properties of cervical cancer cells as well as tumorsphere formation and chemoresistance in vitro. The luciferase reporter assay combined with mutagenesis analyses and Western blotting showed that NF‐YA trans‐activated the expression of SOX2 in cervical cancer. Furthermore, quantitative chromatin immunoprecipitation (qChIP) and electrophoretic mobility shift assay (EMSA) confirmed that NF‐YA protein directly bound to the CCAAT box region located upstream of the SOX2 promoter. Together, our data demonstrated that NF‐YA was highly expressed in cervical cancer and promoted the cell proliferation, tumorigenicity and CSC characteristic by trans‐activating the expression of SOX2.

Comparison of High Doses of Total Body Irradiation in Myeloablative Conditioning before Hematopoietic Cell Transplantation

Malignancy relapse is the most common cause of treatment failure among recipients of hematopoietic cell transplantation (HCT). Conditioning dose intensity can reduce disease relapse but is offset by toxicities. Improvements in radiotherapy techniques and supportive care may translate to better outcomes with higher irradiation doses in the modern era. This study compares outcomes of recipients of increasing doses of high-dose total body irradiation (TBI) divided into intermediate high dose (IH; 13-13.75 Gy) and high dose (HD; 14 Gy) with standard dose (SD; 12 Gy) with cyclophosphamide. A total of 2721 patients ages 18 to 60 years with hematologic malignancies receiving HCT from 2001 to 2013 were included. Cumulative incidences of nonrelapse mortality (NRM) at 5 years were 28% (95% confidence interval [CI], 25% to 30%), 32% (95% CI, 29% to 36%), and 34% (95% CI, 28% to 39%) for SD, IH, and HD, respectively (P = .02). Patients receiving IH-TBI had a 25% higher risk of NRM compared with those receiving SD-TBI (12 Gy) (P = .007). Corresponding cumulative incidences of relapse were 36% (95% CI, 34% to 38%), 32% (95% CI, 29% to 36%), and 26% (95% CI, 21% to 31%; P = .001). Hazard ratios for mortality compared with SD were 1.06 (95% CI, .94 to 1.19; P = .36) for IH and .89 (95% CI, .76 to 1.05; P = .17) for HD. The study demonstrates that despite improvements in supportive care, myeloablative conditioning using higher doses of TBI (with cyclophosphamide) leads to worse NRM and offers no survival benefit over SD, despite reducing disease relapse.

The Role of Eukaryotic and Prokaryotic ABC Transporter Family in Failure of Chemotherapy

Over the years chemotherapy failure has been a vital research topic as researchers have been striving to discover reasons behind it. The extensive studies carried out on chemotherapeutic agents confirm that resistance to chemotherapy is a major reason for treatment failure. “Resistance to chemotherapy,” however, is a comprehensive phrase that refers to a variety of different mechanisms in which ATP-binding cassette (ABC) mediated efflux dominates. The ABC is one of the largest gene superfamily of transporters among both eukaryotes and prokaryotes; it represents a variety of genes that code for proteins, which perform countless functions, including drug efflux – a natural process that protects cells from foreign chemicals. Up to date, chemotherapy failure due to ABC drug efflux is an active research topic that continuously provides further evidence on multiple drug resistance (MDR), aiding scientists in tackling and overcoming this issue. This review focuses on drug resistance by ABC efflux transporters in human, viral, parasitic, fungal and bacterial cells and highlights the importance of the MDR permeability glycoprotein being the mutual ABC transporter among all studied organisms. Current developments and future directions to overcome this problem are also discussed.

Chemosensitization of HepG2 cells by suppression of NF-κB/p65 gene transcription with specific-siRNA

AIM

To investigate small interfering RNA (siRNA)-mediated inhibition of nuclear factor-kappa B (NF-κB) activation and multidrug-resistant (MDR) phenotype formation in human HepG2 cells.

METHODS

Total RNA was extracted from human HepG2 or LO2 cells. NF-κB/p65 mRNA was amplified by nested reverse transcription polymerase chain reaction and confirmed by sequencing. NF-κB/p65 was analyzed by immunohistochemistry. Specific-siRNA was transfected to HepG2 cells to knock down NF-κB/p65 expression. The effects on cell proliferation, survival, and apoptosis were assessed, and the level of NF-κB/p65 or P-glycoprotein (P-gp) was quantitatively analyzed by enzyme-linked immunosorbent assay.

RESULTS

HepG2 cells express NF-κB/p65 and express relatively less phosphorylated p65 (P-p65) and little P-gp. After treatment of HepG2 cells with different doses of doxorubicin, the expression of NF-κB/p65, P-p65, and especially P-gp were dose-dependently upregulated. After HepG2 cells were transfected with NF-κB/p65 siRNA (100 nmol/L), the expression of NF-κB/p65, P-p65, and P-gp were downregulated significantly and dose-dependently. The viability of HepG2 cells was decreased to 23% in the combination NF-κB/p65 siRNA (100 nmol/L) and doxorubicin (0.5 μmol/L) group and 47% in the doxorubicin (0.5 μmol/L) group (t = 7.043, P < 0.001).

CONCLUSION

Knockdown of NF-κB/p65 with siRNA is an effective strategy for inhibiting HepG2 cell growth by downregulating P-gp expression associated chemosensitization and apoptosis induction.

Chemosensitization of HepG2 cells by suppression of NF-κB/p65 gene transcription with specific-siRNA

AIM

To investigate small interfering RNA (siRNA)-mediated inhibition of nuclear factor-kappa B (NF-κB) activation and multidrug-resistant (MDR) phenotype formation in human HepG2 cells.

METHODS

Total RNA was extracted from human HepG2 or LO2 cells. NF-κB/p65 mRNA was amplified by nested reverse transcription polymerase chain reaction and confirmed by sequencing. NF-κB/p65 was analyzed by immunohistochemistry. Specific-siRNA was transfected to HepG2 cells to knock down NF-κB/p65 expression. The effects on cell proliferation, survival, and apoptosis were assessed, and the level of NF-κB/p65 or P-glycoprotein (P-gp) was quantitatively analyzed by enzyme-linked immunosorbent assay.

RESULTS

HepG2 cells express NF-κB/p65 and express relatively less phosphorylated p65 (P-p65) and little P-gp. After treatment of HepG2 cells with different doses of doxorubicin, the expression of NF-κB/p65, P-p65, and especially P-gp were dose-dependently upregulated. After HepG2 cells were transfected with NF-κB/p65 siRNA (100 nmol/L), the expression of NF-κB/p65, P-p65, and P-gp were downregulated significantly and dose-dependently. The viability of HepG2 cells was decreased to 23% in the combination NF-κB/p65 siRNA (100 nmol/L) and doxorubicin (0.5 μmol/L) group and 47% in the doxorubicin (0.5 μmol/L) group (t = 7.043, P < 0.001).

CONCLUSION

Knockdown of NF-κB/p65 with siRNA is an effective strategy for inhibiting HepG2 cell growth by downregulating P-gp expression associated chemosensitization and apoptosis induction.

The effect of radiation exposure on multidrug resistance: in vitro and in vivo studies using non-small lung cancer cells

Background

Technetium-99m methoxyisobutylisonitrile (Tc MIBI) is a substrate with the same uptake kinetics as doxorubicin. Multidrug resistance (MDR) is a mechanism that impedes chemotherapy of non-small cell lung cancer (NSCLC). We examined the effect of radiation exposure on MDR in NSCLC and the synergy between an MDR modulator, GG918, and radiation, using ^99mTc MIBI in vitro and doxorubicin in vivo.

Methods

In vitro NSCLC cells (H1299) were exposed to radiation (3-, 6-, and 9-Gy-irradiated groups) alongside a not-irradiated (0 Gy) group. Technetium-99 metastable methoxyisobutylisonitrile (^99mTc MIBI) was administered to cell suspensions at 48 h after irradiation. Cell radioactivity was measured, and C_in/C_out ratios were calculated and compared. NSCLC cells were also subcutaneously transplanted into the left thigh of nude mice, which were subsequently raised for 2 weeks. Two groups of mice were used: mice exposed to irradiation (9-Gy-irradiated) and those that were not (not-irradiated). Doxorubicin was administered through the caudal vein at 48 h after the irradiation. Using an in vivo imaging system, intratumoural photon counts were measured. To determine the synergy between the MDR modulator and 3- or 6-Gy irradiation, the final GG918 concentration was determined: 0.1 μM (N-H, 3-H, and 6-H groups), 0.001 μM (N-L, 3-L, and 6-L groups), and 0 μM (N-0, 3-0, and 6-0 groups). C_in/C_out ratios were calculated and compared among the groups.

Results

C_in/C_out after 6- or 9-Gy irradiation was significantly higher than that of the not-irradiated group (0 Gy). In vivo, fluorescence photon counts were significantly higher in the tumours of 9-Gy-irradiated mice, up to 270 min after administration of doxorubicin, as compared to the not-irradiated mice. The C_in/C_out ratio in the N-H, 3-H, and 6-H groups was significantly higher than that in the N-0, 3-0, and 6-0 groups. There was no significant difference between C_in/C_out in the N-L group and that of the N-0 group. However, the C_in/C_out ratio in the 3-L and 6-L groups was significantly higher than that in the 3-0 and 6-0 groups.

Conclusions

Irradiation decreased MDR in NSCLC cells. In combination with a low-dose MDR modulator, GG918, MDR transport function was synergistically reduced 48 h post-irradiation.

Modulation of P-glycoprotein efflux pump: induction and activation as a therapeutic strategy

P-glycoprotein (P-gp) is an ATP-dependent efflux pump encoded by the MDR1 gene in humans, known to mediate multidrug resistance of neoplastic cells to cancer therapy. For several decades, P-gp inhibition has drawn many significant research efforts in an attempt to overcome this phenomenon. However, P-gp is also constitutively expressed in normal human epithelial tissues and, due to its broad substrate specificity, to its cellular polarized expression in many excretory and barrier tissues, and to its great efflux capacity, it can play a crucial role in limiting the absorption and distribution of harmful xenobiotics, by decreasing their intracellular accumulation. Such a defense mechanism can be of particular relevance at the intestinal level, by significantly reducing the intestinal absorption of the xenobiotic and, consequently, avoiding its access to the target organs. In this review, the current knowledge on this important efflux pump is summarized, and a new focus is brought on the therapeutic interest of inducing and/or activating P-gp for limiting the toxicity caused by its substrates. Several in vivo and in vitro studies validating the use of such a therapeutic strategy are discussed. An extensive literature search for reported P-gp inducers/activators and for the experimental models used in their characterization was conducted. Those studies demonstrate that effective antidotal pathways can be achieved by efficiently promoting the P-gp-mediated efflux of deleterious xenobiotics, resulting in a significant reduction in their intracellular levels and, consequently, in a significant reduction of their toxicity.

Exploiting sensitization windows of opportunity in hyper and hypo-fractionated radiation therapy

In contrast to the conventional radiotherapy/chemoradiotherapy paradigms used in the treatment of majority of cancer types, this review will describe two areas of radiobiology, hyperfractionated and hypofractionated radiation therapy, for cancer treatment focusing on application of novel concepts underlying these treatment modalities. The initial part of the review discusses the phenomenon of hyper-radiation sensitivity (HRS) at lower doses (0.1 to 0.6 Gy), describing the underlying mechanisms and how this could enhance the effects of chemotherapy, particularly, in hyperfractionated settings. The second part examines the radiobiological/physiological mechanisms underlying the effects of high-dose hypofractionated radiation therapy that can be exploited for tumor cure. These include abscopal/bystander effects, activation of immune system, endothelial cell death and effect of hypoxia with re-oxygenation. These biological properties along with targeted dose delivery and distribution to reduce normal tissue toxicity may make high-dose hypofractionation more effective than conventional radiation therapy for treatment of advanced cancers. The novel radiation physics based methods that take into consideration the tumor volume to be irradiated and normal tissue avoidance/tolerance can further improve treatment outcome and post-treatment quality of life. In conclusion, there is enough evidence to further explore novel avenues to exploit biological mechanisms from hyper-fractionation by enhancing the efficacy of chemotherapy and hypo-fractionated radiation therapy that could enhance tumor control and use imaging and technological advances to reduce toxicity.

Thioredoxin-mediated redox regulation of resistance to endocrine therapy in breast cancer

Resistance to endocrine therapy in breast carcinogenesis due to the redox regulation of the signal transduction system by reactive oxygen species (ROS) is the subject of this review article. Both antiestrogens and aromatase inhibitors are thought to prevent cancer through modulating the estrogen receptor function, but other mechanisms cannot be ruled out as these compounds also block metabolism and redox cycling of estrogen and are free radical scavengers. Endocrine therapeutic agents, such as, tamoxifen and other antiestrogens, and the aromatase inhibitor, exemestane, are capable of producing ROS. Aggressive breast cancer cells have high oxidative stress and chronic treatment with exemestane, fulvestrant or tamoxifen may add additional ROS stress. Breast cancer cells receiving long-term antiestrogen treatment appear to adapt to this increased persistent level of ROS. This, in turn, may lead to the disruption of reversible redox signaling that involves redox-sensitive phosphatases, protein kinases, such as, ERK and AKT, and transcription factors, such as, AP-1, NRF-1 and NF-κB. Thioredoxin modulates the expression of estrogen responsive genes through modulating the production of H2O2 in breast cancer cells. Overexpressing thioredoxine reductase 2 and reducing oxidized thioredoxin restores tamoxifen sensitivity to previously resistant breast cancer cells. In summary, it appears that resistance to endocrine therapy may be mediated, in part, by ROS-mediated dysregulation of both estrogen-dependent and estrogen-independent redox-sensitive signaling pathways. Further studies are needed to define the mechanism of action of thioredoxin modifiers, and their effect on the redox regulation that contributes to restoring the antiestrogen-mediated signal transduction system and growth inhibitory action.

Increased glutathione and mitogen-activated protein kinase phosphorylation are involved in the induction of doxorubicin resistance in hepatocellular carcinoma cells

AIM

  The human hepatocellular carcinoma (HCC) cell line HepG2 can easily acquire resistance to doxorubicin. However, the mechanism of action is unclear.

METHODS

  In the present study, we used confocal microscopy, flow cytometry and other methods to reveal the mechanisms by which HepG2 cells acquire doxorubicin resistance.

RESULTS

  Our results showed that R-HepG2 cells, a doxorubicin-resistant sub-line of HepG2, exhibited decreased intracellular accumulation of doxorubicin and increased expression of P-glycoprotein (P-gp) and multidrug resistance-associated protein 1 when compared with HepG2 cells. R-HepG2 cells also harbored higher levels of glutathione and increased expression of glutathione peroxidase. Furthermore, we demonstrated that the phosphorylation of mitogen-activated protein kinases (p38 and c-jun-N-terminal kinases), IkBα and CREB were increased in R-HepG2 cells. Specific p38 inhibitor SB203580 decreased P-gp expression. The multi-kinase inhibitor sorafenib tosylate also significantly suppressed the phosphorylation of these proteins and inhibited the expression of P-gp.

CONCLUSION

  These findings reveal that the drug resistance could be acquired through mitogen-activated protein kinase-dependent upregulation of P-gp. This mechanism protects R-HepG2 cells from the anticancer action of doxorubicin.

Effect of fractionated irradiation on the expression of multidrug resistance genes in the CNE1 human nasopharyngeal carcinoma cell line

Nasopharyngeal carcinoma (NPC) often develops drug resistance following radiotherapy. The molecular basis of radiotherapy-related multidrug resistance (MDR) remains unclear. In the present study, we investigated the effect of fractionated irradiation on the expression of the MDR-1 gene and the MDR-associated protein P-glycoprotein (P-gp) in CNE1 human NPC cells. CNE1 cells were treated with fractionated X-rays. Drug resistance was determined by MTT assay. The expression levels of MDR-1 and P-gp were analyzed by RT-PCR and western blot analysis, respectively. Differential expression was analyzed by gene chips. The results revealed that low levels of mRNA expression of MDR1 were present in non-irradiated CNE1 cells. Compared with the control, the expression of MDR1 mRNA was gradually increased following fractionated irradiation. On day 21, the expression of MDR1 mRNA was increased 1.59- and 2.19-fold, compared with the control, by treatment with 10 and 20 Gy, respectively. We observed decreased MDR1 expression following treatment with 10 and 20 Gy irradiation on days 28 and 35, compared with day 21. On days 21, 28 and 35, expression was increased 1.37-, 1.40- and 1.15-fold by treatment with 20 Gy compared with 10 Gy. Expression of MDR1 was significantly upregulated by treatment with 50 Gy irradiation compared with the control on days 78 and 106. P-gp expression was consistent with that of MDR1 mRNA expression. The sensitivity of CNE1 cells to cisplatin was reduced following irradiation compared with the control. A total of 26 genes were significantly upregulated and 8 genes were significantly downregulated compared with the control. Results of the present study have shown that MDR1 and P-gp are upregulated in CNE1 cells following irradiation. Multiple genes were involved in the mechanism of radiation-induced drug resistance.

Impact of ABCB1 C3435T polymorphism on lymph node regression in multimodality treatment of locally advanced esophageal cancer

AIMS

Neoadjuvant treatment strategies have been developed to improve the survival of patients with locally advanced esophageal cancer. Since patients with major histopathological response are the ones who mainly benefit from this therapy, we are looking for causes of nonresponse. The multidrug resistance protein ABCB1 belongs to the ATP-binding cassette superfamily of membrane transporters. By exporting positively charged drugs it plays a role in the acquisition of resistance in anticancer therapy. We examined the ABCB1 gene polymorphism C3435T to predict response and prognosis to neoadjuvant radiochemotherapy (cisplatin, 5-fluorouracil and 36 Gy) in locally advanced esophageal cancer patients.

MATERIALS & METHODS

A total of 262 patients (216 male; 46 female; median age: 62 years) with locally advanced esophageal cancer (squamous cell cancer: n = 116, adenocarcinoma: n = 146) were included in this study. All patients received a neoadjuvant radiochemotherapy (36.0 Gy, 5-fluorouracil, cisplatin) followed by surgery. Histomorphologic regression was classified according to the Cologne Regression Grade with major response being classifed as having less than 10% vital tumor cells (n = 107) and minor response when 10% or more vital tumor cells (n = 155) were detected in the surgical specimen. Genomic DNA was extracted from paraffin-embedded tissues of all study patients. Allelic genotyping was performed for ABCB1 rs1045642 by real-time PCR using two allele-specific TaqMan(®) probes in competition. Allelic genotyping was correlated with therapy response and prognosis.

RESULTS

Allelic discrimination revealed a TT genotype in 27%, a CC in 19% and a CT genotype in 54% of the study patients. This SNP was not predictive for response of the primary tumor to neoadjuvant radiochemotherapy. The ABCB1 genotype CC was associated with lymph node formation (p = 0.012) and distant metastases (p = 0.019). Patients with a TT genotype exhibited a significantly less positive lymph node status (ypN1 35%) after chemoradiation compared with patients with a CC (ypN1 = 60%) or CT (ypN1 = 46%) genotype. Moreover, patients bearing the TT genotype exhibited no distant metastasis, while five patients with a CC and two patients with CT genotype had distant metastases. In Kaplan-Meier curves, adenocarcinoma patients with a CC genotype showed a worse survival rate than patients with TT or CT (p = 0.048).

CONCLUSION

Our data supports the impact of ABCB1 on effectiveness of esophageal cancer treatment. SNPs of ABCB1 could be helpful in predicting lymph node regression in the multimodality treatment of locally advanced esophageal cancer.

A unique P-glycoprotein interacting agent displays anticancer activity against hepatocellular carcinoma through inhibition of GRP78 and mTOR pathways

P-glycoprotein (P-gp) overexpression has been demonstrated in many malignancies being a predominant mechanism by which cancer cells develop multidrug resistance. Several categories of P-gp inhibitors have been demonstrated to potentiate anticancer effect induced by cancer chemotherapeutic drugs through competitive inhibition of P-gp pumping activity. Few studies show the agent that selectively acts on P-gp and, by itself, causes cell apoptosis while remain P-gp-deficient cells unaffected. KNG-I-322, a desmosdumotin B derivative, displayed a direct interaction with P-gp and demonstrated selective anti-proliferative and apoptotic activities in P-gp overexpressed Hep3B/VIN other than P-gp-deficient Hep3B cells. KNG-I-322 induced an inhibitory effect on the phosphorylation of mTOR(Ser2448), p70S6K(Thr389) and 4E-BP(Thr37/46) in Hep3B/VIN but not Hep3B cells. The inhibition was fully blocked by the knockdown of P-gp using siRNA techniques. Notably, the P-gp inhibitor, verapamil, also directly interacted with P-gp but significantly diminished KNG-I-322-induced anti-proliferative activity. After the mechanism study, the data showed that KNG-I-322 induced a dramatic down-regulation of GRP78 expression, which was significantly inhibited by verapamil and completely diminished by the knockdown of P-gp. The protein profile analysis of detergent resistant membranes showed that upon the stimulation by KNG-I-322, the level of P-gp expression in non-raft fractions was dramatically increased and, concomitantly, the GRP78 expression was significantly decreased. Taken together, the data suggest that KNG-I-322 induces anticancer activity in Hep3B/VIN cells through a direct interaction with P-gp, leading to the inhibition of mTOR pathways and the induction of GRP78 down-regulation. The data support that KNG-I-322 is a selective anticancer agent against P-gp-overexpressed other than P-gp-deficient cancer cells.

Distinct epigenetic profiling in head and neck squamous cell carcinoma stem cells

OBJECTIVE

To identify unique epigenetic signature in cancer stem cells (CSCs) in head and neck squamous cell carcinoma (HNSCC).

STUDY DESIGN

Molecular and microarray studies.

SETTING

Tertiary referral center.

SUBJECTS AND METHODS

Head and neck CSCs were isolated in HNSCC cells by CD44 staining and flow cytometry sorting. CSCs with highest CD44 expression (CD44(hi)) and non-stem cells (non-SCs) with lowest CD44 expression (CD44(low)) were then characterized for stemness gene expression and their responses to chemotherapeutic agents, followed by high-throughput epigenetic profiling using the Illumina BeadChip Array, targeting 28,544 CpG sites covering more than 14,956 genes.

RESULTS

CD44(hi) CSCs expressed higher levels of stem cell markers and were more resistant to chemotherapeutic agents as compared to CD44(low) non-SCs. By DNA methylation microarray analysis, 17 hypomethylated and 9 hypermethylated genes were identified in CD44(hi) CSCs as compared to non-SCs in most HNSCC cell lines. Cluster analysis using these 26 genes showed that CD44(hi) CSCs were epigenetically distinct from the CD44(low) non-SCs in all 5 HNSCC cell lines.

CONCLUSION

A unique epigenetic profile consisting of 17 hypomethylated and 9 hypermethylated genes was seen in HNSCC CSCs. These genes may be critically required in maintaining the stemness or pluripotency of CSCs and may represent novel molecular targets for anticancer therapies aimed at eradicating CSCs in HNSCC.

Estrogen-induced reactive oxygen species-mediated signalings contribute to breast cancer

Elevated lifetime estrogen exposure is a major risk factor for breast cancer. Recent advances in the understanding of breast carcinogenesis clearly indicate that induction of estrogen receptor (ER) mediated signaling is not sufficient for the development of breast cancer. The underlying mechanisms of breast susceptibility to estrogen's carcinogenic effect remain elusive. Physiologically achievable concentrations of estrogen or estrogen metabolites have been shown to generate reactive oxygen species (ROS). Recent data implicated that these ROS induced DNA synthesis, increased phosphorylation of kinases, and activated transcription factors, e.g., AP-1, NRF1, E2F, NF-kB and CREB of non-genomic pathways which are responsive to both oxidants and estrogen. Estrogen-induced ROS by increasing genomic instability and by transducing signal through influencing redox sensitive transcription factors play important role (s) in cell transformation, cell cycle, migration and invasion of the breast cancer. The present review discusses emerging data in support of the role of estrogen induced ROS-mediated signaling pathways which may contribute in the development of breast cancer. It is envisioned that estrogen induced ROS mediated signaling is a key complementary mechanism that drives the carcinogenesis process. ROS mediated signaling however occurs in the context of other estrogen induced processes such as ER-mediated signaling and estrogen reactive metabolite-associated genotoxicity. Importantly, estrogen-induced ROS can function as independent reversible modifiers of phosphatases and activate kinases to trigger the transcription factors of downstream target genes which participate in cancer progression.

The stem cell code in oral epithelial tumorigenesis: 'the cancer stem cell shift hypothesis'

Tumors of the oral cavity provide an ideal model to study various stages of epithelial tumor progression. A group of cancer cells termed cancer stem cells (CSCs) eludes therapy, persists and initiates recurrence augmenting malignant spread of the disease. Hitherto, accurate identification and separation of such minimal residual cells have proven futile due to lack of identifiable traits to single out these cells from the heterogeneous tumor bulk. In this review we have compiled comprehensive evidence from comparative phenotypic and genotypic studies on normal oral mucosa as well as tumors of different grades to elucidate that differential expression patterns of putative stem cells markers may identify 'minimal residual disease' in oral squamous cell carcinoma. We propose the "cancer stem cell shift hypothesis" to explain the exact identity and switch-over, tumor-promoting mechanisms adapted by putative CSCs with correlation to tumor staging.