Induction of invasion in an organotypic oral cancer model by CoCl2, a hypoxia mimetic

Proton Compared to X-Irradiation Induces Different Protein Profiles in Oral Cancer Cells and Their Derived Extracellular Vesicles

Extracellular vesicles (EVs) are membrane-bound particles released from cells, and their cargo can alter the function of recipient cells. EVs from X-irradiated cells have been shown to play a likely role in non-targeted effects. However, EVs derived from proton irradiated cells have not yet been studied. We aimed to investigate the proteome of EVs and their cell of origin after proton or X-irradiation. The EVs were derived from a human oral squamous cell carcinoma (OSCC) cell line exposed to 0, 4, or 8 Gy from either protons or X-rays. The EVs and irradiated OSCC cells underwent liquid chromatography-mass spectrometry for protein identification. Interestingly, we found different protein profiles both in the EVs and in the OSCC cells after proton irradiation compared to X-irradiation. In the EVs, we found that protons cause a downregulation of proteins involved in cell growth and DNA damage response compared to X-rays. In the OSCC cells, proton and X-irradiation induced dissimilar cell death pathways and distinct DNA damage repair systems. These results are of potential importance for understanding how non-targeted effects in normal tissue can be limited and for future implementation of proton therapy in the clinic.

The metastatic capacity of high-grade serous ovarian cancer cells changes along disease progression: inhibition by mifepristone

BACKGROUND

Simplistic two-dimensional (2D) in vitro assays have long been the standard for studying the metastatic abilities of cancer cells. However, tri-dimensional (3D) organotypic models provide a more complex environment, closer to that seen in patients, and thereby provide a more accurate representation of their true capabilities. Our laboratory has previously shown that the antiprogestin and antiglucocorticoid mifepristone can reduce the growth, adhesion, migration, and invasion of various aggressive cancer cells assessed using 2D assays. In this study, we characterize the metastatic capabilities of high-grade serous ovarian cancer cells generated along disease progression, in both 2D and 3D assays, and the ability of cytostatic doses of mifepristone to inhibit them.

METHODS

High-grade serous ovarian cancer cells collected from two separate patients at different stages of their disease were used throughout the study. The 2D wound healing and Boyden chamber assays were used to study migration, while a layer of extracellular matrix was added to the Boyden chamber to study invasion. A 3D organotypic model, composed of fibroblasts embedded in collagen I and topped with a monolayer of mesothelial cells was used to further study cancer cell adhesion and mesothelial displacement. All assays were studied in cells, which were originally harvested from two patients at different stages of disease progression, in the absence or presence of cytostatic doses of mifepristone.

RESULTS

2D in vitro assays demonstrated that the migration and invasive rates of the cells isolated from both patients decreased along disease progression. Conversely, in both patients, cells representing late-stage disease demonstrated a higher adhesion capacity to the 3D organotypic model than those representing an early-stage disease. This adhesive behavior is associated with the in vivo tumor capacity of the cells. Regardless of these differences in adhesive, migratory, and invasive behavior among the experimental protocols used, cytostatic doses of mifepristone were able to inhibit the adhesion, migration, and invasion rates of all cells studied, regardless of their basal capabilities over simplistic or organotypic metastatic in vitro model systems. Finally, we demonstrate that when cells acquire the capacity to grow spontaneously as spheroids, they do attach to a 3D organotypic model system when pre-incubated with conditioned media. Of relevance, mifepristone was able to cause dissociation of these multicellular structures.

CONCLUSION

Differences in cellular behaviours were observed between 2 and 3D assays when studying the metastatic capabilities of high-grade serous ovarian cancer cells representing disease progression. Mifepristone inhibited these metastatic capabilities in all assays studied.

The Art of Inducing Hypoxia

Many cells in the human body strongly react on decreased oxygen concentrations, generally defined as hypoxia. Therefore, inducing hypoxia in vitro is essential for research. Classically, hypoxia is induced using a hypoxia chamber, but alternative methods exist that do not require special equipment. Here, we compared three different methods to induce hypoxia without a hypoxia chamber: the chemical stabilization of HIF-1α by CoCl2, the decrease in pericellular oxygen concentrations by increased media height, and the consumption of oxygen by an enzymatic system. Hypoxia induction was further analyzed within three different cell culture systems: 2D (adherent) osteoprogenitor cells, monocytic (suspension) cells, and in a 3D in vitro fracture hematoma model. The different methods were analyzed within the scope of fracture healing regarding inflammation and differentiation. We could show that all three induction methods were feasible for hypoxia induction within adherent cells. Increased media heights did not stimulate a hypoxic response within suspension cells and in the 3D system. Chemical stabilization of HIF-1α showed limitations when looking at the expression of cytokines in osteoprogenitors and monocytes. Enzymatic reduction of oxygen proofed to be most effective within all three systems inducing inflammation and differentiation.

Hydrogen Sulfide Protects against Chemical Hypoxia-Induced Injury via Attenuation of ROS-Mediated Ca2+ Overload and Mitochondrial Dysfunction in Human Bronchial Epithelial Cells

Oxidative stress induced by hypoxia/ischemia resulted in the excessive reactive oxygen species (ROS) and the relative inadequate antioxidants. As the initial barrier to environmental pollutants and allergic stimuli, airway epithelial cell is vulnerable to oxidative stress. In recent years, the antioxidant effect of hydrogen sulfide (H₂S) has attracted much attention. Therefore, in this study, we explored the impact of H₂S on CoCl₂-induced cell injury in 16HBE14o- cells. The effect of CoCl₂ on the cell viability was detected by Cell Counting Kit (CCK-8) and the level of ROS in 16HBE14o- cells in response to varying doses (100–1000 μmol/L) of CoCl₂ (a common chemical mimic of hypoxia) was measured by using fluorescent probe DCFH-DA. It was shown that, in 16HBE14o- cells, CoCl₂ acutely increased the ROS content in a dose-dependent manner, and the increased ROS was inhibited by the NaHS (as a donor of H₂S). Moreover, the calcium ion fluorescence probe Fura-2/AM and fluorescence dye Rh123 were used to investigate the intracellular calcium concentration ([Ca²⁺]_i) and mitochondria membrane potential (MMP) in 16HBE14o- cells, respectively. In addition, we examined apoptosis of 16HBE14o- cells with Hoechst 33342. The results showed that the CoCl₂ effectively elevated the Ca²⁺ influx, declined the MMP, and aggravated apoptosis, which were abrogated by NaHS. These results demonstrate that H₂S could attenuate CoCl₂-induced hypoxia injury via reducing ROS to perform an agonistic role for the Ca²⁺ influx and MMP dissipation.

The protective effects of propofol against CoCl2-induced HT22 cell hypoxia injury via PP2A/CAMKIIα/nNOS pathway

Background

Perioperative cerebral ischemia/hypoxia could induce hippocampal injury and has been reported to induce cognitive impairment. In this study, we used cobalt chloride (CoCl₂) to build a hypoxia model in mouse hippocampal cell lines. Propofol, a widely used intravenous anesthetic agent, has been demonstrated to have neuroprotective effect. Here, we explored whether and how propofol attenuated CoCl₂-induced mouse hippocampal HT22 cell injury.

Methods

Mouse hippocampal HT22 cells were pretreated with propofol, and then stimulated with CoCl₂. Cell viability was measured by cell counting kit 8 (CCK8). The effect of propofol on CoCl₂-modulated expressions of B-cell lymphoma 2 (Bcl-2), BAX, cleaved caspase 3, phosphatase A2 (PP2A), and the phosphorylation of Ca²⁺/Calmodulin (CaM)-dependent protein kinase II (pCAMKIIα), neuron nitric oxide synthase at Ser¹⁴¹² (pnNOS-Ser¹⁴¹²), neuron nitric oxide synthase at Ser⁸⁴⁷ (pnNOS-Ser⁸⁴⁷) were detected by Western blot analysis.

Results

Compared with control, CoCl₂ treatment could significantly decrease cell viability, which could be reversed by propofol. Further, we found CoCl₂ treatment could up-regulate the expression of PP2A, BAX, cleaved caspase three and cause the phosphorylation of nNOS-Ser¹⁴¹², but it down-regulated the expression of Bcl-2 and the phosphorylation of CAMKIIα and nNOS-Ser⁸⁴⁷. More importantly, these CoCl₂-mediated effects were attentuated by propofol. In addition, we demonstrated that propofol could exert similar effect to that of the PP2A inhibitor (okadaic acid). Further, the PP2A activator (FTY720) and the CAMKIIα inhibitor (KN93) could reverse the neuroprotective effect of propofol.

Conclusion

Our data indicated that propofol could attenuate CoCl₂-induced HT22 cells hypoxia injury via PP2A/CAMKIIα/nNOS pathway.

Silencing HIF-1α aggravates growth inhibition and necrosis of proximal renal tubular epithelial cell under hypoxia

The kidney is particularly susceptible to ischemia/hypoxia insult while dysfunction of proximal tubular epithelial cells (PTEC) is a primary pathologic hallmark in acute kidney injury. Hypoxia-inducible factor-1 (HIF-1) is a key regulator responsible for cellular hypoxic responses. Therefore, we investigated the effects of HIF-1 suppression, using small interference RNA (siRNA), upon the cell fate of PTEC under hypoxia, and explored the underlying possible molecular mechanism. Hypoxia was induced with hypoxia mimetic cobalt chloride. Our data showed that, in HIF-1α siRNA group, the HK-2 cells growth inhibition and necrosis became worse than those in hypoxia group. However, for apoptosis, no significant difference was observed between them. Consistent with the downregulation of HIF-1α in HIF-1α siRNA group, both mRNA and protein expression of glucose transporter-1 (Glut-1) and vascular endothelial growth factor (VEGF) also reduced more significantly than those in hypoxia group. In conclusion, silencing HIF-1α gene could aggravate growth inhibition and necrosis of PTEC under hypoxia. We provide evidence, from the opposite direction, that HIF-1 activation under hypoxia may facilitate adaptation and survival of proximal renal tubular cells, and the beneficial effects may be related to its downstream genes, such as Glut-1 and VEGF.

Nuclear translocation and activation of YAP by hypoxia contributes to the chemoresistance of SN38 in hepatocellular carcinoma cells

Although hypoxia is a prominent feature contributing to the therapeutic resistance of hepatocellular carcinoma cells (HCC) against chemotherapeutic agents, including the Topoisomerase I inhibitor SN38, the underlying mechanism is not fully understood and its understanding remains a major clinical challenge. In the present study, we found that hypoxia-induced nuclear translocation and accumulation of YAP acted as a survival input to promote resistance to SN38 in HCC. The induction of YAP by hypoxia was not mediated by HIF-1α because manipulating the abundance of HIF-1α with CoCl2, exogenous expression, and RNA interference had no effect on the phosphorylation or total levels of YAP. The mevalonate-HMG-CoA reductase (HMGCR) pathway may modulate the YAP activation under hypoxia. Combined YAP inhibition using either siRNA or the HMGCR inhibitor statins together with SN38 treatment produced improved anti-cancer effects in HCC cells. The increased anti-cancer effect of the combined treatment with statins and irinotecan (the prodrug of SN-38) was further validated in a human HepG2 xenograft model of HCC in nude mice. Taken together, our findings identify YAP as a novel mediator of hypoxic-resistance to SN38. These results suggest that the administration of SN28 together with the suppression of YAP using statins is a promising strategy for enhancing the treatment response in HCC patients, particularly in advanced stage HCC cases presenting hypoxic resistance.

Caveolin-1 accumulation in the tongue cancer tumor microenvironment is significantly associated with poor prognosis: an in-vivo and in-vitro study

Background

Caveolin-1 (CAV1) may be upregulated by hypoxia and acts in a tumor-dependent manner. We investigated CAV1 in tongue squamous cell carcinoma (TSCC) and its association with clinical outcomes, and studied in vitro possible ways for CAV1 accumulation in the tumor microenvironment (TME).

Methods

TSCC cases (N = 64) were immunohistochemically stained for CAV1. Scores were separately assessed in the tumor and TME and plotted for association with recurrence and survival (univariate analysis with log-rank test). In vitro studies were performed on a 3D myoma organotypic model, a mimicker of TME. Prior to monoculturing HSC-3 tongue cancer cells, the model underwent modifications in oxygenation level (1%O₂ hypoxia to upregulate CAV1) and/or in the amount of natural soluble factors [deleted by 14-day rinsing (rinsed myoma, RM), to allow only HSC-3-derived factors to act]. Controls included normoxia (21%O₂) and naturally occurring soluble factors (intact myoma, IM). HSC-3 cells were also co-cultured with CaDEC12 cells (fibroblasts exposed to human tongue cancer). CAV1 expression and cellular distribution were examined in different cellular components in hypoxic and rinsed myoma assays. Twist served as a marker for the process of epithelial-mesenchymal transition (EMT). Exosomes isolated from HSC-3 media were investigated for containing CAV1.

Results

Expression of CAV1 in TSCC had a higher score in TME than in the tumor cells and a negative impact on recurrence (p = 0.01) and survival (p = 0.003). Monocultures of HSC-3 revealed expression of CAV1 mainly in the TME-like myoma assay, similar to TSCC. CAV1+, alpha-smooth muscle actin (αSMA) + and Twist + CAF-like cells were observed surrounding the invading HSC-3, possibly reflecting EMT. RM findings were similar to IM, inferring action of HSC-3 derived factors, and no differences were seen when hypoxia was induced. HSC-3-CaDEC12 co-cultures revealed CAV1+, αSMA+ and cytokeratin-negative CAF-like cells, raising the possibility of CaDEC12 cells gaining a CAF phenotype. HSC-3-derived exosomes were loaded with CAV1.

Conclusions

Accumulation of CAV1-TME in TSCC had a negative prognostic value. In vitro studies showed the presence of CAV1 in cancer cells undergoing EMT and in fibroblasts undergoing trans-differentiation to CAFs. CAV1 delivery to the TME involved cancer cell-derived exosomes.

Hypoxia-induced cell stemness leads to drug resistance and poor prognosis in lung adenocarcinoma

BACKGROUND

Since cancer stem cells exhibit embryonic-like self-renewal characteristics and malignant behavior, including drug resistance and metastasis, they may be the origin of tumorigenesis and cancer recurrence. Cancer cell stemness is also highly relevant to cancer in hypoxic environments.

METHODS

In our study, we used cobalt dichloride (CoCl2) to create a hypoxic environment for lung adenocarcinoma A549 cells and the cisplatine-resistant cell line A549/DDP. The cancer stem-like CD166 positive population and the cells' stemness were detected by flowcytometry and quantitative real-time PCR after separation using magnetic antibodies. Drug resistance to cisplatine, docetaxel and pemetrexed was also measured. Finally, a tissue array was used to analyze the relationship between hypoxia-induced stemness and overall survival after radical surgery.

RESULTS

Data showed that chemical-induced hypoxia changed cell stemness by enhancing stem cell transcription factors and markers of chemotherapeutic drug resistance. The CD166-positive cancer stem cell-like population showed greater drug resistance than the CD166-negative cells. Tissue array studies also suggested a poorer prognosis for patients whose tissue expressed higher CD166 levels.

CONCLUSION

Our findings indicate that chemical hypoxia may augment cancer cell stemness and drug resistance in CD166-positive stem cells. Therefore, targeting the stem-like cell population, especially CD166-positive cells, may represent a novel therapeutic strategy to treat lung cancer.

Role of LPAR3, PKC and EGFR in LPA-induced cell migration in oral squamous carcinoma cells

Background

Oral squamous cell carcinoma is an aggressive neoplasm with serious morbidity and mortality, which typically spreads through local invasive growth. Lysophosphatidic acid (LPA) is involved in a number of biological processes, and may have a role in cancer cell migration and invasiveness. LPA is present in most tissues and can activate cells through six different LPA receptors (LPAR1-6). Although LPA is predominantly promigratory, some of the receptors may have antimigratory effects in certain cells. The signalling mechanisms of LPA are not fully understood, and in oral carcinoma cells the specific receptors and pathways involved in LPA-stimulated migration are unknown.

Methods

The oral carcinoma cell lines E10, SCC-9, and D2 were investigated. Cell migration was studied in a scratch wound assay, and invasion was demonstrated in organotypic three dimensional co-cultures. Protein and mRNA expression of LPA receptors was studied with Western blotting and qRT-PCR. Activation of signalling proteins was examined with Western blotting and isoelectric focusing, and signalling mechanisms were further explored using pharmacological agents and siRNA directed at specific receptors and pathways.

Results

LPA stimulated cell migration in the two oral carcinoma cell lines E10 and SCC-9, but was slightly inhibitory in D2. The receptor expression profile and the effects of specific pharmacological antagonist and agonists indicated that LPA-stimulated cell migration was mediated through LPAR3 in E10 and SCC-9. Furthermore, in both these cell lines, the stimulation by LPA was dependent on PKC activity. However, while LPA induced transactivation of EGFR and the stimulated migration was blocked by EGFR inhibitors in E10 cells, LPA did not induce EGFR transactivation in SCC-9 cells. In D2 cells, LPA induced EGFR transactivation, but this was associated with slowing of a very high inherent migration rate in these cells.

Conclusion

The results demonstrate LPA-stimulated migration in oral carcinoma cells through LPAR3, mediated further by PKC, which acts either in concert with or independently of EGFR transactivation.

Transforming growth factor β1 signal is crucial for dedifferentiation of cancer cells to cancer stem cells in osteosarcoma

Human osteosarcoma harbors a small subpopulation of cancer stem cells (CSCs) that is believed to be associated with tumor metastasis, radioresistance/chemoresistance, local invasion, and poor clinical outcome. In this study, we found that transforming growth factor β1 (TGF-β1) signaling and a hypoxic environment dramatically induced self-renewal capacity in non-stem osteosarcoma cells, which in turn promoted chemoresistance, tumorigenicity, neovasculogenesis, and metastatic potential. Furthermore, blocking the TGF-β1 signaling pathway resulted in the inhibition of the dedifferentiation and clonogenicity of osteosarcoma cells, and the reduction of CSC self-renewal capacity and hypoxia-mediated dedifferentiation. These findings demonstrate that stem cells and non-stem cells exist in a dynamic equilibrium within the osteosarcoma cell population, and that CSCs may develop de novo from differentiated cancer cells. Hierarchical models of mammalian CSCs, therefore, should be considered to serve as bidirectional interconversion between the stem and non-stem cell components of the tumor.

The hypoxic tumor microenvironment regulates invasion of aggressive oral carcinoma cells

Invasion is an important hallmark of cancer involving interactions between the tumor microenvironment and the cancer cells. Hypoxia, low oxygen level, is related to increased invasion and metastasis in many cancers. The aim was to elucidate the effect of hypoxia on invasion of oral squamous cell carcinoma cells (OSCCs), and the applicability of a novel 3-dimentional myoma organotypic invasion model in hypoxia experiments. OSCC cell lines (primary oral carcinoma derived cells UT-SCC-43A, recurrent oral carcinoma cells UT-SCC-43B and aggressive tongue carcinoma cells HSC-3) were studied for their migration and invasion capabilities under normoxia, hypoxia, and in the presence a hypoxia-mimicker cobalt chloride. As expected, the recurrent UT-SCC-43B cells were significantly more aggressive than the primary tumor derived cells. In contrast to tongue carcinoma HSC-3 cells, they only mildly responded to hypoxia in the migration or invasion assays, indicating a cell line specific response of hypoxia on the invasive potential. The modification of the organotypic human tissue-derived matrix via the removal of various yet unidentified soluble factors by rinsing the tissue resulting in stripped matrix substantially changed the invasion pattern of HSC-3 cells and the outcomes of hypoxic treatments. Only in the stripped tissue hypoxia significantly increased invasion, whereas in native intact tissue the induced invasion was not observed. This demonstrates the importance of the soluble factors to the invasion pattern and to the hypoxia response. A metastasis and poor prognosis marker, hypoxia-regulated lysyl oxidase (LOX), was present in the myoma tissue, but could be removed by rinsing. The inhibition of LOX resulted in a decrease in invasion area, but only very mildly in invasion depth. Thus, it may have a role in the modulation of the invasion pattern. Another hypoxia-related poor prognosis marker carbonic anhydrase 9 (CAIX) was induced in HSC-3 cells both by the hypoxic exposure and interestingly in invading HSC-3 cells inside the tissue even in normoxic conditions. In conclusion, this suggests that the intact myoma organotypic model offers optimally hypoxic surroundings, thus being an excellent human tumor microenvironment mimicker.

Evidence for premature aging due to oxidative stress in iPSCs from Cockayne syndrome

Cockayne syndrome (CS) is a human premature aging disorder associated with neurological and developmental abnormalities, caused by mutations mainly in the CS group B gene (ERCC6). At the molecular level, CS is characterized by a deficiency in the transcription-couple DNA repair pathway. To understand the role of this molecular pathway in a pluripotent cell and the impact of CSB mutation during human cellular development, we generated induced pluripotent stem cells (iPSCs) from CSB skin fibroblasts (CSB-iPSC). Here, we showed that the lack of functional CSB does not represent a barrier to genetic reprogramming. However, iPSCs derived from CSB patient's fibroblasts exhibited elevated cell death rate and higher reactive oxygen species (ROS) production. Moreover, these cellular phenotypes were accompanied by an up-regulation of TXNIP and TP53 transcriptional expression. Our findings suggest that CSB modulates cell viability in pluripotent stem cells, regulating the expression of TP53 and TXNIP and ROS production.

Up-regulation of hypoxia-inducible factor-1 alpha by cobalt chloride prevents hearing loss in noise-exposed mice

Since hypoxia-inducible factor-1α (HIF-1α) is the key transcription factor that enables cells to survive in hypoxia, we have investigated whether an upregulation of HIF-1α prevents the noise-induced hearing loss in BALB/c hybrid mice, which were intraperitoneally injected with CoCl(2) (a HIF-1α inducer) and exposed to white band noise with 120 dB peak equivalent sound pressure level for 3h once daily for 3 days. In the CoCl(2) treatment group, HIF-1α was found to be up-regulated in the cochlear tissues and the hearing loss was largely prevented. Histologically, the loss of sensory hair cells was also significantly lower in the CoCl(2) treatment group than the Control group. However, YC-1 (a HIF-1α inhibitor) attenuated the preventive effect of CoCl(2) on the noise-induced hearing loss. These results suggest that HIF-1α plays a crucial role in the prevention against noise trauma in the inner ear.