Human papillomavirus 16 E6 increases the radiosensitivity of p53-mutated cervical cancer cells, associated with up-regulation of aurora A

Biology of the Radio- and Chemo-Responsiveness in HPV Malignancies

In multiple anatomic sites, patients with cancers associated with the Human Papillomavirus (HPV) experience better locoregional control and overall survival after radiotherapy and/or chemoradiotherapy than patients with HPV-negative cancers. These improved outcomes suggest that relatively unique biological features in HPV-positive cancers may increase sensitivity to DNA damaging agents as well as an impaired DNA damage response. This review will address potential biological mechanisms driving this increased sensitivity of HPV-positive cancer to radiation and/or chemotherapy. This review will discuss the clinical and preclinical observations that support the intrinsic radiosensitivity and/or chemosensitivity of HPV-positive cancers. Furthermore, this review will highlight the molecular mechanisms for increased radiation sensitivity using the classical "4 Rs" of radiobiology: repair, reassortment, repopulation, and reoxygenation. First, HPV-positive cancers have increased DNA damage due to increased oxidative stress and impaired DNA damage repair due to the altered activity TP53, p16, TIP60, and other repair proteins. Second, irradiated HPV-positive cancer cells display increased G2/M arrest leading to reassortment of cancer cells in more radiosensitive phases of the cell cycle. In addition, HPV-positive cancers have less radioresistant cancer stem cell subpopulations that may limit their repopulation during radiotherapy. Finally, HPV-positive cancers may also have less hypoxic tumor microenvironments that make these cancers more sensitive to radiation than HPV-negative cells. We will also discuss extrinsic immune and microenvironmental factors enriched in HPV-positive cancers that facilities responses to radiation. Therefore, these potential biological mechanisms may underpin the improved clinical outcomes often observed in these virally induced cancers.

Therapeutic potential of p53 reactivation in cervical cancer

Cervical cancer (CC) is one of most common malignancies affecting women worldwide. To date, surgical resection is the only effective radical remedy for CC at its early stages, while the prognosis of metastatic or recurrent CC is very poor. Dysfunction of the tumor suppressor p53 due to aberrant expression, post-translational modification, mutations, SNPs, and LOH as well as sequestration by viral antigens and MDM2/HDM2-mediated degradation is closely associated with the therapeutic insensitivity and relapse of many malignancies, including CC. Accumulating studies have demonstrated that restoration of p53 activity can induce cell cycle arrest and apoptosis, eliminate radio- and chemotherapy resistance, and inhibit tumor growth in CC cells. Therefore, activation of wild-type p53 as well as restoration of p53 function seems appealing as a therapeutic strategy. In this review, we focus on the potential roles of p53 reactivation in CC treatment and their underlying molecular mechanisms towards the development of novel therapies.

Nimotuzumab Combined With Irradiation Enhances the Inhibition to the HPV16 E6-Promoted Growth of Cervical Squamous Cell Carcinoma

Human papillomavirus (HPV) 16 E6 has been proved to increase the radiosensitivity and lead to the EGFR overexpression in cervical cancer cells. In this study, to investigate the inhibition of nimotuzumab-mediated EGFR blockade combined with radiotherapy, we established a C33A cervical squamous cell line overexpressed HPV16-E6 and a nude mouse model bearing these cell lines. The CCK-8 assay was used to detect the effects of various treatments on the proliferation of C33A cells. Flow cytometry was used to detect the rates of apoptosis and cell cycle arrest. Gene transcription and protein expression were detected by quantitative real-time polymerase chain reaction (qRT-PCR) and western blot, respectively. Immunohistochemical staining was used to evaluate protein expression in tumor tissue. We revealed that E6-overexpressing C33A cells grew faster and were more sensitive to radiotherapy than control cells in vitro and in vivo. The expression levels of EGFR, as well as those of downstream signaling molecules AKT and ERK 1/2, were significantly upregulated in C33A cells that overexpressed E6. We observed that nimotuzumab combined with radiotherapy could enhance the inhibition of C33A cell growth induced by E6, both in vitro and in vivo. We also observed enhanced effect after combination on G2/M cell cycle arrest and apoptosis in E6-overexpressing C33A cells. Furthermore, the combined therapy of nimotuzumab and radiation remarkably reduced the protein expression levels of EGFR, AKT, ERK 1/2 in vitro, and in vivo. In conclusion, HPV16 E6 expression is positively correlated with levels of EGFR, AKT, and ERK 1/2 protein expression. The combined treatment with nimotuzumab and radiotherapy to enhance radiosensitivity in E6-positive cervical squamous cell carcinoma was related to enhanced G2/M cell cycle arrest and caspase-related apoptosis.

Comparative RNA sequencing reveals that HPV16 E6 abrogates the effect of E6*I on ROS metabolism

High-risk Human Papillomavirus infections are responsible for anogenital and oropharyngeal cancers. Alternative splicing is an important mechanism controlling HPV16 gene expression. Modulation in the splice pattern leads to polycistronic HPV16 early transcripts encoding a full length E6 oncoprotein or truncated E6 proteins, commonly named E6*. Spliced E6*I transcripts are the most abundant RNAs produced in HPV-related cancers. To date, the biological function of the E6*I isoform remains controversial. In this study, we identified, by RNA sequencing, cellular targets deregulated by E6*I, among which genes related to ROS metabolism. Concomitantly, E6*I-overexpressing cells display high levels of ROS. However, co-overexpression of both E6 and E6*I has no effect on ROS production. In HPV16-infected cells expressing different E6/E6*I levels, we show that the newly identified targets CCL2 and RAC2 are increased by E6*I but decreased by E6 expression, suggesting that E6 abrogates the effect of E6*I. Taken together, these data support the idea that E6*I acts independently of E6 to increase ROS production and that E6 has the ability to counteract the effects of E6*I. This asks the question of how E6*I can be considered separately of E6 in the natural history of HPV16 infection.

Derlin1 functions as an oncogene in cervical cancer via AKT/mTOR signaling pathway

BACKGROUND

Cervical cancer (CC) ranks third in the morbidity and mortality of female cancer around the world. Derlin1 has been found to be overexpressed in several human cancers. However, it is still unclear about its roles in CC. The research aims to explore the relationship between Derlin1 and CC.

METHODS

We purchased a human CC tissues microarray, which contained CC tissues and corresponding para-cancerous tissues from 93 patients with primary cervical squamous cell carcinoma. Immunohistochemical staining was used to confirm the expression of Derlin1 in these tissues. And we detected the differential expression of Derlin1 in cervical cancer cell lines and normal cervical epithelial cells (H8). Further, the cervical cancer cell lines SiHa and C33A were used as an in vitro model, which was down-regulated the expression of Derlin1 using siRNA interference technology. The effects of Derlin1 down-regulating in CC cell lines on cell proliferation and migration were detected by CCK8 assay and transwell assay, respectively. The effect of Derlin1 down-regulating on apoptosis was analyzed by flow cytometry, and apoptosis-related proteins were detected using western blotting. In-depth mechanisms were studied using western blotting. In addition, the effects of Derlin1 up-regulating in normal cervical epithelial cells also were exposed.

RESULTS

Derlin1 was significantly elevated in CC tissues (81.7%, 76/93), and the expression of Derlin1 was positively correlated with the tumor size, pathological grade, and lymph node metastasis in CC patients. And Derlin1 was high expressed in cervical cancer cell lines compared to H8 cells. Knockdown of Derlin1 in cervical cancer cell lines inhibited cell proliferation and migration. Moreover, knockdown of Derlin1 induced apoptosis and affected the expression of apoptosis-related proteins, including Bcl-2, Bax, Bim, caspase3 and caspase9. Further experiments showed that AKT/mTOR signal pathway might be involve in this processes that knockdown of Derlin1 inhibited the expression of p-AKT and p-mTOR. Over-expression of Derlin1 in H8 cells promoted cell proliferation and migration via up-regulated the expression of p-AKT and p-mTOR.

CONCLUSION

Derlin1 is an oncogene in CC via AKT/mTOR pathway. It might be a potential therapeutic target for CC.

A new role for Drosophila Aurora-A in maintaining chromosome integrity

Aurora-A is a conserved mitotic kinase overexpressed in many types of cancer. Growing evidence shows that Aurora-A plays a crucial role in DNA damage response (DDR) although this aspect has been less characterized. We isolated a new aur-A mutation, named aur-A⁹⁴⁹, in Drosophila, and we showed that it causes chromosome aberrations (CABs). In addition, aur-A⁹⁴⁹ mutants were sensitive to X-ray treatment and showed impaired γ-H2Av foci dissolution kinetics. To identify the pathway in which Aur-A works, we conducted an epistasis analysis by evaluating CAB frequencies in double mutants carrying aur-A⁹⁴⁹ mutation combined to mutations in genes related to DNA damage response (DDR). We found that mutations in tefu (ATM) and in the histone variant H2Av were epistatic over aur-A⁹⁴⁹ indicating that Aur-A works in DDR and that it is required for γ-H2Av foci dissolution. More interestingly, we found that a mutation in lig4, a gene belonging to the non-homologous end joining (NHEJ) repair pathway, was epistatic over aur-A⁹⁴⁹. Based on studies in other systems, which show that phosphorylation is important to target Lig4 for degradation, we hypothesized that in aur-A⁹⁴⁹ mutant cells, there is a persistence of Lig4 that could be, in the end, responsible for CABs. Finally, we observed a synergistic interaction between Aur-A and the homologous recombination (HR) repair system component Rad 51 in the process that converts chromatid deletions into isochromatid deletions. Altogether, these data indicate that Aur-A depletion can elicit chromosome damage. This conclusion should be taken into consideration, since some anticancer therapies are aimed at reducing Aurora-A expression.

Value of Diffusion-Weighted Magnetic Resonance Imaging Combined with miR-18a Level in Predicting Radiosensitivity of Cervical Cancer

Background

Radioresistance during radiotherapy of cervical cancer often leads to treatment failure; therefore, there is an urgent need to develop effective predictive indicators of radiosensitivity for cervical cancer patients.

Material/Methods

Cervical cancer cells were collected from 40 patients who received surgical resections. The relationships between apparent diffusion coefficient (ADC) values of masses before surgery and different micro-RNAs (miRNA) levels (miR-18a, miR-132, and miR-145) of these cells were investigated. Cervical cancer cells were divided into 4 groups according to the ADC values of original tumor tissues and expression level of miR-18a. Then, these cells were exposed with irradiation both in vitro and in vivo.

Results

Advanced cervical cancer showed lower ADC values in magnetic resonance imaging. miR-18a, miR-132, and miR-145 all were increased in the cervical cancer tissues, while miR-18a showed a more marked negative correlation with ADC values. The results of in vitro and in vivo assays showed that higher expression of miR-18a in cervical cancer cells leads to more radiosensitivity, especially in cells from cancer tissues with lower ADC values.

Conclusions

The combination of ADC values with expression level of miR-18a may be a new and reliable predictor for radiosensitivity of cervical cancer, helping cervical cancer patients with low ADC values and high expressions of miR-18a to achieve better outcomes in radiotherapy.

Association between human papilloma virus/Epstein-Barr virus coinfection and oral carcinogenesis

BACKGROUND

The recent epidemic of head and neck squamous cell carcinomas associated with human papilloma virus (HPV) has not addressed its association with lymphoid tissue in the oropharynx or the potential role of Epstein-Barr virus (EBV)/HPV coinfection.

METHODS

The prevalence of HPV and EBV infection/coinfection and CD21 mRNA expression were determined in normal and cancerous tissues from the oropharynx using in situ hybridization (ISH), p16, and quantitative reverse transcriptase PCR (qRT-PCR). The effects of coinfection on tumorigenicity were evaluated using proliferation and invasion assays.

RESULTS

Normal oropharynx, tonsil, non-cancer base of tongue (BOT), and BOT from sleep apnea patients demonstrated EBV positivity ranging from 7% to 36% depending on the site and methods of detection used (qRT-PCR or ISH). Among non-malignant BOT samples, HPV positivity was noted only in 20%. The percent of tonsil and BOT cancers positive for HPV (up to 63% and 80%, respectively) or coinfected with HPV/EBV (up to 25% and 70%, respectively) were both significantly associated with cancer status. Notably, HPV/EBV coinfection was observed only in malignant tissue originating in lymphoid-rich oropharynx sites (tonsil, BOT). CD21 mRNA (the major EBV attachment receptor) was detected in tonsil and BOT epithelium, but not in soft-palate epithelium. Coinfected cell lines showed a significant increase in invasiveness (P < 0.01).

CONCLUSIONS

There is a high prevalence of HPV/EBV infection and coinfection in BOT and tonsil cancers, possibly reflecting their origins in lymphoid-rich tissue. In vitro, cells modeling coinfection have an increased invasive potential.

Aurora-A: a potential DNA repair modulator

It is well-known that overexpression of Aurora-A promotes tumorigenesis, but the role of Aurora-A in the development of cancer has not been fully investigated. Recent studies indicate that Aurora-A may confer cancer cell chemo- and radioresistance through dysregulation of cell cycle progression and DNA damage response. Direct evidences from literatures suggest that Aurora-A inhibits pRb, p53, p21(waf1/cip1), and p27(cip/kip) but enhances Plk1, CDC25, CDK1, and cyclin B1 to repeal cell cycle checkpoints and to promote cell cycle progression. Other studies indicate that Aurora-A suppresses BRCA1, BRCA2, RAD51, poly(ADP ribose) polymerase (PARP), and gamma-H2AX to dysregulate DNA damage response. Aurora-A may also interact with RAS and Myc to control DNA repair indirectly. In this review, we summarized the potential role of Aurora-A in DNA repair from the current literatures and concluded that Aurora-A may function as a DNA repair modulator to control cancer cell radio- and chemosensitivity, and that Aurora-A-associated DNA repair molecules may be considered for targeted cancer therapy.

Ectopic expression of miR-34a enhances radiosensitivity of non-small cell lung cancer cells, partly by suppressing the LyGDI signaling pathway

miR-34a is transcriptionally induced by the tumor suppressor gene p53, which is often downregulated in non-small cell lung cancer (NSCLC). To address whether the downstream signal of miR-34a is sufficient to induce apoptosis and to alter cellular radiosensitivity, a chemical synthetic miR-34a mimic was delivered into A549 and H1299 cells, with or without co-treatment of γ-irradiation. Results showed that ectopic expression of miR-34a induced dose-dependent cell growth inhibition and apoptosis in a p53-independent manner in both NSCLC cell lines. Interestingly, LyGDI was discovered as a new target gene of miR-34a, and downregulation of LyGDI promoted Rac1 activation and membrane translocation, resulting in cell apoptosis. Furthermore, restoration of miR-34a indirectly reduced cyclooxygenase-2 (COX-2) expression. Taken together, these results demonstrate that restoration of miR-34a expression enhances radiation-induced apoptosis, partly by suppressing the LyGDI signaling pathway, and miR-34a could possibly be used as a radiosensitizer for non-small cell lung cancer therapy.

A novel carbazole derivative, MHY407, sensitizes cancer cells to doxorubicin-, etoposide-, and radiation treatment via DNA damage

In this study, we synthesized a novel carbazole derivative, MHY407, as a sensitizer of cancer cells to increase DNA damage. We then evaluated the anticancer effects of MHY407 and identified the molecular mechanism for the sensitization of breast cancer cell lines. MHY407 significantly increased DNA damage as determined by DNA breakage, levels of damage-responsive proteins, and DNA foci. In addition, MHY407 increased p21 and decreased cyclin D1 protein levels. MHY407 also involved increased cell cycle arrest at the S phase. Furthermore, in doxorubicin and etoposide-treated breast cancer cells, co-treatment with MHY407 reduced cell viability and increased apoptosis. Co-treatment of MHY407 with doxorubicin or etoposide increased DNA damage-related proteins and foci formation, suggesting that increased DNA damage by MHY407 plays an important role in the sensitization. In addition, MHY407 also sensitized the cancer cells to DNA damaging radiation treatment. These results may contribute to the development of MHY407-based treatments for cancer patients receiving DNA-damage therapy.

Characteristics and survival of head and neck cancer by HPV status: a cancer registry-based study

Elucidation of the role of human papillomavirus (HPV) in the etiology and prognosis of squamous carcinomas of the head and neck (HNSCC) is essential to optimize prevention and treatment strategies for this disease. We analyzed 385 HNSCC tissue blocks identified through a population-based cancer registry in Metropolitan Detroit for HPV DNA using a broad-spectrum PCR technique (SPF10-LiPA25) to correlate with patient and tumor characteristics and overall survival. Overall, HPV DNA (any type) was detected in 29.4% of all HNSCC, but it was significantly more prevalent (50.6%) in oropharyngeal sites (N=81), where 90% of HPV were type 16, than in other sites. HPV prevalence (any type) in oropharyngeal sites was highest in patients with a negative smoking indicator, Caucasians and in regional tumor stage. Likewise, only in oropharyngeal sites did patients overall positive to HPV show significantly better survival compared with HPV-negative patients, notably among those who had been irradiated. The best and the worst survival from cancer in oropharyngeal sites were found, respectively, among HPV-positive patients with negative smoking indicator and among HPV-negative patients with positive smoking indicator. The results of this study revealed that the presence of HPV DNA was associated with patients' specific characteristics and better overall survival exclusively in oropharyngeal sites. To define the fraction of HNSCC preventable by HPV vaccination or amenable to less aggressive treatment, however, tobacco exposure and HPV markers other than DNA presence need to be taken into account.

Salinomycin, a p-glycoprotein inhibitor, sensitizes radiation-treated cancer cells by increasing DNA damage and inducing G2 arrest

Salinomycin (Sal) is potentially useful for the treatment of cancer. The present study examined a novel mechanism of Sal sensitization in cancer cells. Sal sensitized radiation-treated cancer cells by inducing G2 arrest and causing DNA damage. Sal treatment also reduced p21 levels in radiation-treated cells. Considering that Sal sensitizes doxorubicin (DOX)- or etoposide (ETO)-treated cancer cells by causing DNA damage and reducing p21 expression, the results from our study suggest that the mechanism underlying Sal sensitization is conserved in both chemo- and radiation-treated cells. We also tested the ability of Sal to inhibit p-glycoprotein (P-gp), which plays a role in the efflux of anti-cancer drugs to reduce cellular damage. In particular, we compared Sal to verapamil (Ver), a well-known P-gp inhibitor. Sal inhibits P-gp with a different substrate distinct from that of Ver. In addition, Sal sensitized Ver-resistant cells, indicating that this compound is more effective for sensitizing than Ver. Taken together, the results from our study may contribute to the development of Sal-based therapy for cancer patients treated with P-gp-inhibiting drugs or radiation therapy.

MiR-34a in age and tissue related radio-sensitivity and serum miR-34a as a novel indicator of radiation injury

MiR-34a, a direct target of p53, has shown to exert potent anti-proliferative effects. It has also been found that miR-34a can be induced by irradiation in vitro and in vivo. However, the relationship between miR-34a and radio-sensitivity, and its potential diagnostic significance in radiation biology, remain unclear. This study found that differing responses to ionizing radiation (IR) of young and adult mice were related to miR-34a. First, we found that miR-34a could be induced in many organs by radiation of both young and adult mice. However, the level of miR-34a induced by young mice was much higher when compared to adult mice. Next, we found that miR-34a played a critical role in radio-sensitivity variations of different tissues by enhancing cell apoptosis and decreasing cell viability. We also found that the induction of miR-34a by radiation was in a p53 dependent manner and that one possible downstream target of miR-34a that lead to different radio-sensitivity was the anti-apoptosis molecular Bcl-2. However, over-expression of miR-34a and knockdown of Bcl-2 could significantly enhance the radio-sensitivity of different cells while inhibition of miR-34a could protect cells from radiation injury. Finally, we concluded that miR-34a could be stable in serum after IR and serve as a novel indicator of radiation injury. Taken together, this data strongly suggests that miR-34a may be a novel indicator, mediator and target of radiation injury, radio-sensitivity and radioprotection.