Establishment of a human squamous cell carcinoma cell line of the upper aero-digestive tract

Recurrent UBE3C-LRP5 translocations in head and neck cancer with therapeutic implications

Head and neck cancer is a major cause of morbidity and mortality worldwide. The identification of genetic alterations in head and neck cancer may improve diagnosis and treatment outcomes. In this study, we report the identification and functional characterization of UBE3C-LRP5 translocation in head and neck cancer. Our whole transcriptome sequencing and RT-PCR analysis of 151 head and neck cancer tumor samples identified the LRP5-UBE3C and UBE3C-LRP5 fusion transcripts in 5.3% of patients of Indian origin (n = 151), and UBE3C-LRP5 fusion transcripts in 1.2% of TCGA-HNSC patients (n = 502). Further, whole genome sequencing identified the breakpoint of UBE3C-LRP5 translocation. We demonstrate that UBE3C-LRP5 fusion is activating in vitro and in vivo, and promotes the proliferation, migration, and invasion of head and neck cancer cells. In contrast, depletion of UBE3C-LRP5 fusion suppresses the clonogenic, migratory, and invasive potential of the cells. The UBE3C-LRP5 fusion activates the Wnt/β-catenin signaling by promoting nuclear accumulation of β-catenin, leading to upregulation of Wnt/β-catenin target genes, MYC, CCND1, TCF4, and LEF1. Consistently, treatment with the FDA-approved drug, pyrvinium pamoate, significantly reduced the transforming ability of cells expressing the fusion protein and improved survival in mice bearing tumors of fusion-overexpressing cells. Interestingly, fusion-expressing cells upon knockdown of CTNNB1, or LEF1 show reduced proliferation, clonogenic abilities, and reduced sensitivity to pyrvinium pamoate. Overall, our study suggests that the UBE3C-LRP5 fusion is a promising therapeutic target for head and neck cancer and that pyrvinium pamoate may be a potential drug candidate for treating head and neck cancer harboring this translocation.

Modifying gap junction communication in cancer therapy

AIM

Drug delivery is crucial for therapeutic efficacy and gap junction communication channels (GJIC) facilitate movement within the tumour. Pro-drug activation, a modality of cancer therapy leads to Ganciclovir triphosphate (GCV-TP) incorporation into newly synthesized DNA resulting in cell death. The objective was to enhance, with Histone deacetylase inhibitors (HDACi) and All Trans Retinoic Acid (ATRA), GJIC, crucial for drug delivery, and with combination, abrogate the observed detrimental effect of Dexamethasone (DXM).

METHODS

Cell lines (NT8E, and HeLa) were pre-treated with Valproic Acid (VPA) (1 mM), 4 Phenyl Butyrate (4PB) (2 mM), ATRA (10 μM) and Dexamethasone (1 μM). Protein quantitated with the Bicinchoninic (BCA) assay for cell lysates, membrane and soluble fractions was assessed with Western blotting for Connexins (43, 26 and 32) and E-Cadherin. A qRT-PCR was done for CX 43-GJA1, CX 26-GJB2, CX 32-GJB1 and E-Cadherin, and normalized with Glyceraldehyde Phosphate dehydrogenase (GAPDH). Further, localization of Connexins (CX) and E-Cadherin, GJIC competence, pre-clinical in-vitro studies and the mechanism of cell death were evaluated.

RESULTS

There was no toxicity or change in growth patterns observed with the drugs. In both the cell lines CX 43 localized to the membrane whereas CX 32 and CX 26 were present but not membrane bound. E-Cadherin was present on the membrane in NT8E and completely absent in HeLa cells. Effects of HDACi, DXM and ATRA were seen on the expression of Connexins and E-Cadherin in both the cell lines. NT8E and HeLa cell lines showed enhanced GJIC with 4PB [30 %], VPA [36 %] and ATRA [54 %] with a 60 % increase in cytotoxicity and an abrogation of Dexamethasone inhibition on combination with VPA or ATRA.

CONCLUSION

An enhancement of GJIC function by HDACi and ATRA increased cytotoxicity and could be effective in the presence of Dexamethasone, when combined with ATRA or VPA.

An Assay to Assess Gap Junction Communication in Cell Lines

This protocol was developed to assess communication in tumor cells and to provide a dependable and standardized assay for the in vitro determination of gap junction function. The method is noninvasive; in this method, the cell population under study is divided such that 1 fraction is loaded with a lipophilic cell plasma membrane permeable dye, calcein acetoxymethyl ester, that is hydrolyzed upon cellular uptake by cytoplasmic esterases to yield calcein, a fluorescent and membrane-impermeable molecule. The other fraction is loaded with 1,1'-dioctadecyl-3,3,3',3' tetramethylindodicarbocyanine perchlorate (DiD)/1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate [Dil; DilC₁₈(3)], which is a lipophilic membrane dye that diffuses laterally to stain the entire cell membrane, is impermeable, and attains an orange-red fluorescence upon incorporation into membranes. The 2 fractions are mixed and incubated under coculture conditions. Calcein with MW 890 kD is transferred to the DiD/DiI-stained cells through gap junctions. The assessment of this uptake is made with confocal imaging and quantitated using flow cytometry. Cell lines representing cancer of the breast as well as a nontransformed cell line developed from the buccal mucosa were analyzed for gap junction competency. Confocal imaging with acquisition at specific time points during the in vitro treatment and flow cytometry gave a qualitative and quantitative analysis of the passage of molecules through the gap junctions. Here, the method has been combined to obtain images as well as quantitation and is a simple and effective approach in assessing the functional competency of gap junction in epithelial cells.

Enhancement of radiosensitivity of oral carcinoma cells by iodinated chlorin p6 copper complex in combination with synchrotron X-ray radiation

The combination of synchrotron X-ray radiation and metal-based radiosensitizer is a novel form of photon activation therapy which offers the advantage of treating malignant tumors with greater efficacy and higher precision than conventional radiation therapy. In this study the anticancer cytotoxic efficacy of a new chlorophyll derivative, iodinated chlorin p₆ copper complex (ICp₆-Cu), combined with synchrotron X-ray radiation (8-10 keV) in two human oral cancer cell lines is explored. Pre-treatment of cells with 20 µM and 30 µM ICp₆-Cu for 3 h was found to enhance the X-ray-induced cytotoxicity with sensitization enhancement ratios of 1.8 and 2.8, respectively. ICp₆-Cu localized in cytoplasm, mainly in lysosomes and endoplasmic reticulum, and did not cause any cytotoxicity alone. The radiosensitization effect of ICp₆-Cu accompanied a significant increase in the level of reactive oxygen species, damage to lysosomes, inhibition of repair of radiation-induced DNA double-strand breaks, increase in cell death and no significant effect on cell cycle progression. These results demonstrate that ICp₆-Cu is a potential agent for synchrotron photon activation therapy of cancer.

Hydrophobically modified polyethylenimine-based ternary complexes for targeting brain tumor: stability, in vitro and in vivo studies

Hydrophobic modification of low molecular weight polyethylenimine (PEI 2 kDa) by cholic acid (ChA) was done to obtain PEI2-ChA. The nanoplexes of PEI2-ChA with gWIZ-GFP demonstrated increase transfection efficiency (∼27%) in NT8e cell lines. The cell-cycle analysis of NT8e cells (p53 mutant) treated with transferrin containing nanoplexes showed increased apoptosis of cells. In vitro protein expression revealed expression of exogenous p53 protein. In vivo imaging of mice showed localized signal for GFP protein in brain region. The tumors of mice treated with transferrin containing nanoplexes of PEI2-ChA were ∼5 times smaller in size than the tumor of untreated animals.

Dual drug loaded nanoliposomal chemotherapy: A promising strategy for treatment of head and neck squamous cell carcinoma

The rising incidence of head and neck cancer and the drawbacks of currently used therapeutic strategies such as salvage surgery followed by adjuvant chemo- or radiotherapy have encouraged pursuits for better therapeutic approaches. This work describes the development and characterization of a PEGylated liposomal nanocarrier encapsulated with trans-resveratrol (Res), a plant stilbenoid, and doxorubicin hydrochloride (Dox), a standard chemotherapeutic agent for treatment of oral squamous cell carcinoma. The two drugs were loaded in liposomes prepared from egg phosphatidylcholine and DSPE-PEG with maximum encapsulation efficiencies of about 80% for each drug achieved at Res to Dox ratio of 2:1. The liposomal suspension was found to be stable with a zeta potential of -30.53 mV and size of approximately 250 nm. Thermal properties and release kinetics of the dual drug loaded liposomes were determined. The nanoformulation was evaluated for its in vitro anticancer efficacy on an oral squamous cell carcinoma cell line (NT8e). The cell uptake mechanism of the liposomal formulation was determined using pharmacological inhibitors for different endocytosis pathways. The combination effect of the two drugs was evaluated in free form and was found to have synergistic effects. The formulation was found to have a higher IC50 value than that of free doxorubicin hydrochloride but was found to have a superior effect on the signaling proteins involved in apoptosis and cell cycle.

Integrated genomics approach to identify biologically relevant alterations in fewer samples

BACKGROUND

Several statistical tools have been developed to identify genes mutated at rates significantly higher than background, indicative of positive selection, involving large sample cohort studies. However, studies involving smaller sample sizes are inherently restrictive due to their limited statistical power to identify low frequency genetic variations.

RESULTS

We performed an integrated characterization of copy number, mutation and expression analyses of four head and neck cancer cell lines - NT8e, OT9, AW13516 and AW8507 - by applying a filtering strategy to prioritize for genes affected by two or more alterations within or across the cell lines. Besides identifying TP53, PTEN, HRAS and MET as major altered HNSCC hallmark genes, this analysis uncovered 34 novel candidate genes altered. Of these, we find a heterozygous truncating mutation in Nuclear receptor binding protein, NRBP1 pseudokinase gene, identical to as reported in other cancers, is oncogenic when ectopically expressed in NIH-3 T3 cells. Knockdown of NRBP1 in an oral carcinoma cell line bearing NRBP1 mutation inhibit transformation and survival of the cells.

CONCLUSIONS

In overall, we present the first comprehensive genomic characterization of four head and neck cancer cell lines established from Indian patients. We also demonstrate the ability of integrated analysis to uncover biologically important genetic variation in studies involving fewer or rare clinical specimens.

NGS-based approach to determine the presence of HPV and their sites of integration in human cancer genome

BACKGROUND

Human papilloma virus (HPV) accounts for the most common cause of all virus-associated human cancers. Here, we describe the first graphic user interface (GUI)-based automated tool 'HPVDetector', for non-computational biologists, exclusively for detection and annotation of the HPV genome based on next-generation sequencing data sets.

METHODS

We developed a custom-made reference genome that comprises of human chromosomes along with annotated genome of 143 HPV types as pseudochromosomes. The tool runs on a dual mode as defined by the user: a 'quick mode' to identify presence of HPV types and an 'integration mode' to determine genomic location for the site of integration. The input data can be a paired-end whole-exome, whole-genome or whole-transcriptome data set. The HPVDetector is available in public domain for download: http://www.actrec.gov.in/pi-webpages/AmitDutt/HPVdetector/HPVDetector.html.

RESULTS

On the basis of our evaluation of 116 whole-exome, 23 whole-transcriptome and 2 whole-genome data, we were able to identify presence of HPV in 20 exomes and 4 transcriptomes of cervical and head and neck cancer tumour samples. Using the inbuilt annotation module of HPVDetector, we found predominant integration of viral gene E7, a known oncogene, at known 17q21, 3q27, 7q35, Xq28 and novel sites of integration in the human genome. Furthermore, co-infection with high-risk HPVs such as 16 and 31 were found to be mutually exclusive compared with low-risk HPV71.

CONCLUSIONS

HPVDetector is a simple yet precise and robust tool for detecting HPV from tumour samples using variety of next-generation sequencing platforms including whole genome, whole exome and transcriptome. Two different modes (quick detection and integration mode) along with a GUI widen the usability of HPVDetector for biologists and clinicians with minimal computational knowledge.

Novel resveratrol and 5-fluorouracil coencapsulated in PEGylated nanoliposomes improve chemotherapeutic efficacy of combination against head and neck squamous cell carcinoma

Increasing consumption of tobacco and alcohol has led to a steady increase in the incidence of head and neck cancers in Asia. The drawbacks associated with the existing chemotherapeutic and surgical interventions have necessitated the development of a safer alternative for therapy of head and neck cancers. In this study we have explored the synergistic therapeutic potential of a phytochemical and chemotherapeutic agent using PEGylated liposomes as a delivery vehicle. Resveratrol and 5-fluorouracil were successfully coencapsulated in a single PEGylated nanoliposome. The thermal analysis and the nuclear magnetic resonance results revealed that resveratrol localized near the glycerol backbone of the liposomal membrane while 5-fluorouracil localized closer to the phosphate moiety, which influenced the release kinetics of both drugs. The nanoformulation was tested in vitro on a head and neck cancer cell line NT8e and was found to exhibit a GI₅₀ similar to that of free 5-fluorouracil. Further, gene expression studies showed that the combination of resveratrol and 5-fluorouracil exhibited different effects on different genes that may influence the net antagonistic effect. The coencapsulation of resveratrol and 5-fluorouracil in a liposomal nanocarrier improved the cytotoxicity in comparison with the free drug combination when tested in vitro.

Conjugation of chlorin p(6) to histamine enhances its cellular uptake and phototoxicity in oral cancer cells

PURPOSE

Our previous studies in hamster cheek pouch model have shown that chlorin p (6) (Cp (6)), a chlorophyll derivative is a suitable photosensitizer for photodynamic treatment (PDT) of small tumors (<5 mm). However, for bigger tumors, the accumulation of Cp (6) was inadequate, which compromised the effectiveness of PDT. The purpose of present study was to investigate the possibility of improving the cellular uptake of Cp (6) by conjugating it to histamine, a biogenic amine that is known to modulate tumor growth and development via cell surface receptors.

METHODS

The conjugate of Cp (6) and histamine (Cp (6)-his) was prepared by carbodiimide coupling reaction. Cellular uptake, intracellular localization and cytotoxicity of both Cp (6) and its conjugate were investigated in two human oral cancer cell lines (4451 and NT8e). The percentage of necrotic and apoptotic cells after PDT were also estimated using Hoechst 33342-propidium iodide staining.

RESULTS

In both the cell line, the cellular uptake of Cp (6)-his was found to be ~10 times higher when compared to Cp (6). Histamine led to a slight increase in intracellular uptake of Cp (6)-his, whereas ranitidine, a histamine H2 receptor antagonist, and incubation at lower temperature (~15°C) led to its inhibition, suggesting that uptake of Cp (6)-his is receptor mediated. Results on western blot confirmed the presence of H2 receptor in both the cell line. Observations on intracellular localization revealed that unlike Cp (6), which localized on multiple sites, Cp (6)-his showed localization on the cell membrane and around the perinuclear region. Moreover, the phototoxicity induced by Cp (6)-his was ~4 times higher when compared to Cp (6) in both the cell lines. There was, however, no significant difference in the mode of cell death.

CONCLUSION

Results suggest that conjugating Cp (6) with histamine can help improve the effectiveness of PDT in oral cancer cells by enhancing its intracellular delivery.

Down-regulation of survivin by oxaliplatin diminishes radioresistance of head and neck squamous carcinoma cells

BACKGROUND

Oxaliplatin is integrated in treatment strategies against a variety of cancers including radiation protocols. Herein, as a new strategy we tested feasibility and rationale of oxaliplatin in combination with radiation to control proliferation of head and neck squamous cell carcinoma (HNSCC) cells and discussed survivin-related signaling and apoptosis induction.

METHODS

Cytotoxicity and apoptosis induced by radiation and/or oxaliplatin were examined in relation to survivin status using two HNSCC cell lines viz., Cal27 and NT8e, and one normal 293-cell line. Survivin gene knockdown by siRNA was also tested in relevance to oxaliplatin-mediated radiosensitization effects.

RESULTS

Survivin plays a critical role in mediating radiation-resistance in part through suppression of apoptosis via a caspase-dependent mechanism. Oxaliplatin treatment significantly decreased expression of survivin in cancer cells within 24-72 h. Apoptotic cells and caspase-3 activity were increased parallely with decrease in cell viability, if irradiated during this sensitive period. The cytotoxicity of oxaliplatin and radiation combination was greater than additive. Survivin gene knockdown experiments have demonstrated the role of survivin in radiosensitization of cancer cells mediated by oxaliplatin.

CONCLUSIONS

Higher expression of survivin is a critical factor for radioresistance in HNSCC cell lines. Pre-treatment of cancer cells with oxaliplatin significantly increased the radiosensitivity through induction of apoptosis by potently inhibiting survivin.

HDAC inhibitor valproic acid enhances tumor cell kill in adenovirus-HSVtk mediated suicide gene therapy in HNSCC xenograft mouse model

Safety, efficacy and enhanced transgene expression are the primary concerns while using any vector for gene therapy. One of the widely used vectors in clinical trials is adenovirus which provides a safe way to deliver the therapeutic gene. However, adenovirus has poor transduction efficiency in vivo since most tumor cells express low coxsackie and adenovirus receptors. Similarly transgene expression remains low, possibly because of the chromatization of adenoviral genome upon infection in eukaryotic cells, an effect mediated by histone deacetylases (HDACs). Using a recombinant adenovirus (Ad-HSVtk) carrying the herpes simplex thymidine kinase (HSVtk) and GFP genes we demonstrate that HDAC inhibitor valproic acid can bring about an increase in CAR expression on host cells and thereby enhanced Ad-HSVtk infectivity. It also resulted in an increase in transgene (HSVtk and GFP) expression. This, in turn, resulted in increased cell kill of HNSCC cells, following ganciclovir treatment in vitro as well as in vivo in a xenograft nude mouse model.

Cyclin D1 downregulation is important for permanent cell cycle exit and initiation of differentiation induced by anchorage-deprivation in human keratinocytes

To understand the relationship between permanent cell cycle exit and differentiation the immortalized keratinocyte cell line, SIK and the squamous cell carcinoma, SCC9 were compared during differentiation induced by anchorage-deprivation. The SIK cells when placed in suspension culture promptly lost almost all ability to reinitiate growth by 2 days concomitantly expressing the differentiation specific proteins, transglutaminase (TGK) and involucrin. These cells rapidly underwent G1 cell cycle arrest with complete disappearance of phosphorylated RB. In contrast SCC9 cells neither showed TGK expression nor increase in involucrin. They decreased their colony-forming ability much more slowly, which coordinated well with a gradual decrease in phosphorylated RB, demonstrating the significant resistance to loss of colony-forming ability and cell cycle exit. In accordance, cyclin D1, a positive regulator of cyclin-dependent kinase (CDK) 4/6 which phosphorylates RB decreased drastically in anchorage deprived SIK but not in SCC9 cells. Endogenous cyclin D1 knockdown in SCC9 cells by siRNA enhanced loss of the colony-forming ability during anchorage-deprivation. Conversely enforced expression of cyclin D1 in SIK cells and in another immortalized keratinocyte cell line, HaCaT, partly prevented loss of their colony-forming abilities. Cyclin D1 overexpression antagonized Keratin 10 expression in suspended HaCaT cells. The result demonstrates the importance of cyclin D1 down regulation for proper initiation of keratinocyte differentiation.