Neocarzinostatin induces an effective p53-dependent response in human papillomavirus-positive cervical cancer cells

Activation of p53-regulated pro-survival signals and hypoxia-independent mitochondrial targeting of TIGAR by human papillomavirus E6 oncoproteins

The high-risk subtype human papillomaviruses (hrHPVs) infect and oncogenically transform basal epidermal stem cells associated with the development of squamous-cell epithelial cancers. The viral E6 oncoprotein destabilizes the p53 tumor suppressor, inhibits p53 K120-acetylation by the Tat-interacting protein of 60 kDa (TIP60, or Kat5), and prevents p53-dependent apoptosis. Intriguingly, the p53 gene is infrequently mutated in HPV + cervical cancer clinical isolates which suggests a possible paradoxical role for this gatekeeper in viral carcinogenesis. Here, we demonstrate that E6 activates the TP53-induced glycolysis and apoptosis regulator (TIGAR) and protects cells against oncogene-induced oxidative genotoxicity. The E6 oncoprotein induces a Warburg-like stress response and activates PI3K/PI5P4K/AKT-signaling that phosphorylates the TIGAR on serine residues and induces its hypoxia-independent mitochondrial targeting in hrHPV-transformed cells. Primary HPV + cervical cancer tissues contain high levels of TIGAR, p53, and c-Myc and our xenograft studies have further shown that lentiviral-siRNA-knockdown of TIGAR expression inhibits hrHPV-induced tumorigenesis in vivo. These findings suggest the modulation of p53 pro-survival signals and the antioxidant functions of TIGAR could have key ancillary roles during HPV carcinogenesis.

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.

Artemisinin Represses Telomerase Subunits and Induces Apoptosis in HPV-39 Infected Human Cervical Cancer Cells

Artemisinin, a plant-derived antimalarial drug with relatively low toxicity on normal cells in humans, has selective anticancer activities in various types of cancers, both in vitro and in vivo. In the present study, we have investigated the anticancer effects of artemisinin in human cervical cancer cells, with special emphasis on its role in inducing apoptosis and repressing cell proliferation by inhibiting the telomerase subunits, ERα which is essential for maintenance of the cervix, and downstream components like VEGF, which is known to activate angiogenesis. Effects of artemisinin on apoptosis of ME-180 cells were measured by flow cytometry, DAPI, and annexin V staining. Expression of genes and proteins related to cell proliferation and apoptosis was quantified both at the transcriptional and translational levels by semi-quantitative RT-PCR and western blot analysis, respectively. Our findings demonstrated that artemisinin significantly downregulated the expression of ERα and its downstream component, VEGF. Antiproliferative activity was also supported by decreased telomerase activity and reduced expression of hTR and hTERT subunits. Additionally, artemisinin reduced the expression of the HPV-39 viral E6 and E7 components. Artemisinin-induced apoptosis was confirmed by FACS, nuclear chromatin condensation, annexin V staining. Increased expression of p53 with concomitant decrease in expression of the p53 inhibitor Mdm2 further supported that artemisinin-induced apoptosis was p53-dependent. The results clearly indicate that artemisinin induces antiproliferative and proapoptotic effects in HPV-39-infected ME-180 cells, and warrants further trial as an effective anticancer drug.

Tanshinone IIA inhibits viral oncogene expression leading to apoptosis and inhibition of cervical cancer

Human papilloma virus (HPV) is the well-established etiological factor of cervical cancer. E6 and E7 oncoproteins expressed by HPV are known to inactivate tumor suppressor proteins p53 and pRb, respectively. Tanshinone IIA (Tan IIA) is a diterpenoid naphthoquinone found in the traditional Chinese medicine Danshen (Salvia sp.). Tan IIA has been shown to possess anti-tumor activity against several cancer types. In this study we show that Tan IIA potently inhibited proliferation of the human cervical cancer CaSki, SiHa, HeLa and C33a cells. Mechanistically in HPV positive CaSki cells, Tan IIA was found to (i) downregulate expression of HPV E6 and E7 genes and modulate associated proteins E6AP and E2F1, (ii) cause S phase cell cycle arrest, (iii) induce accumulation of p53 and alter expression of p53-dependent targets, (iv) modulate pRb and related proteins, and (v) cause p53-mediated apoptosis by moderating Bcl2, Bax, caspase-3, and PARP cleavage expressions. In vivo, Tan IIA resulted in over 66% reduction in tumor volume of cervical cancer xenograft in athymic nude mice. Tan IIA treated tumor tissues had lower expression of proliferation marker PCNA and changes in apoptosis targets were in agreement with in vitro studies, further confirming reduced proliferation and involvement of multiple targets behind anti-cancer effects. This is the first demonstration of Tan IIA to possess significant anti-viral activity by repressing HPV oncogenes leading to inhibition of cervical cancer. Together, our data suggest that Tan IIA can be exploited as a potent therapeutic agent for the prevention and treatment of cervical and other HPV-related cancers.

Genus beta human papillomavirus E6 proteins vary in their effects on the transactivation of p53 target genes

The genus beta human papillomaviruses (beta HPVs) cause cutaneous lesions and are thought to be involved in the initiation of some nonmelanoma skin cancers (NMSCs), particularly in patients with the genetic disorder epidermodysplasia verruciformis (EV). We have previously reported that at least two of the genus beta HPV E6 proteins bind to and/or increase the steady-state levels of p53 in squamous epithelial cells. This is in contrast to a well-characterized ability of the E6 proteins of cancer-associated HPVs of genus alpha HPV, which inactivate p53 by targeting its ubiquitin-mediated proteolysis. In this study, we have investigated the ability of genus beta E6 proteins from eight different HPV types to block the transactivation of p53 target genes following DNA damage. We find that the E6 proteins from diverse beta HPV species and types vary in their capacity to block the induction of MDM2, p21, and proapoptotic genes after genotoxic stress. We conclude that some genus beta HPV E6 proteins inhibit at least some p53 target genes, although perhaps not by the same mechanism or to the same degree as the high-risk genus alpha HPV E6 proteins.

IMPORTANCE

This study addresses the ability of various human papillomavirus E6 proteins to block the activation of p53-responsive cellular genes following DNA damage in human keratinocytes, the normal host cell for HPVs. The E6 proteins encoded by the high-risk, cancer-associated HPV types of genus alpha HPV have a well-established activity to target p53 degradation and thereby inhibit the response to DNA damage. In this study, we have investigated the ability of genus beta HPV E6 proteins from eight different HPV types to block the ability of p53 to transactivate downstream genes following DNA damage. We find that some, but not all, genus beta HPV E6 proteins can block the transactivation of some p53 target genes. This differential response to DNA damage furthers the understanding of cutaneous HPV biology and may help to explain the potential connection between some beta HPVs and cancer.

In situ molecular identification of the influenza A (H1N1) 2009 Neuraminidase in patients with severe and fatal infections during a pandemic in Mexico City

Background

In April 2009, public health surveillance detected an increased number of influenza-like illnesses in Mexico City’s hospitals. The etiological agent was subsequently determined to be a spread of a worldwide novel influenza A (H1N1) triple reassortant. The purpose of the present study was to demonstrate that molecular detection of pandemic influenza A (H1N1) 2009 strains is possible in archival material such as paraffin-embedded lung samples.

Methods

In order to detect A (H1N1) virus sequences in archived biological samples, eight paraffin-embedded lung samples from patients who died of pneumonia and respiratory failure were tested for influenza A (H1N1) Neuraminidase (NA) RNA using in situ RT-PCR.

Results

We detected NA transcripts in 100% of the previously diagnosed A (H1N1)-positive samples as a cytoplasmic signal. No expression was detected by in situ RT-PCR in two Influenza-like Illness A (H1N1)-negative patients using standard protocols nor in a non-related cervical cell line. In situ relative transcription levels correlated with those obtained when in vitro RT-PCR assays were performed. Partial sequences of the NA gene from A (H1N1)-positive patients were obtained by the in situ RT-PCR-sequencing method. Sequence analysis showed 98% similarity with influenza viruses reported previously in other places.

Conclusions

We have successfully amplified specific influenza A (H1N1) NA sequences using stored clinical material; results suggest that this strategy could be useful when clinical RNA samples are quantity limited, or when poor quality is obtained. Here, we provide a very sensitive method that specifically detects the neuraminidase viral RNA in lung samples from patients who died from pneumonia caused by Influenza A (H1N1) outbreak in Mexico City.

DNA double strand breaks but not interstrand crosslinks prevent progress through meiosis in fully grown mouse oocytes

There is some interest in how mammalian oocytes respond to different types of DNA damage because of the increasing expectation of fertility preservation in women undergoing chemotherapy. Double strand breaks (DSBs) induced by ionizing radiation and agents such as neocarzinostatin (NCS), and interstrand crosslinks (ICLs) induced by alkylating agents such as mitomycin C (MMC), are toxic DNA lesions that need to be repaired for cell survival. Here we examined the effects of NCS and MMC treatment on oocytes collected from antral follicles in mice, because potentially such oocytes are readily collected from ovaries and do not need to be in vitro grown to achieve meiotic competency. We found that oocytes were sensitive to NCS, such that this ionizing radiation mimetic blocked meiosis I and caused fragmented DNA. In contrast, MMC had no impact on the completion of either meiosis I or II, even at extremely high doses. However, oocytes treated with MMC did show γ-H2AX foci and following their in vitro maturation and parthenogenetic activation the development of the subsequent embryos was severely compromised. Addition of MMC to 1-cell embryos caused a similarly poor level of development, demonstrating oocytes have eventual sensitivity to this ICL-inducing agent but this does not occur during their meiotic division. In oocytes, the association of Fanconi Anemia protein, FANCD2, with sites of ICL lesions was not apparent until entry into the embryonic cell cycle. In conclusion, meiotic maturation of oocytes is sensitive to DSBs but not ICLs. The ability of oocytes to tolerate severe ICL damage and yet complete meiosis, means that this type of DNA lesion goes unrepaired in oocytes but impacts on subsequent embryo quality.

SAFROLE OXIDE INDUCES APOPTOSIS IN A549 HUMAN LUNG CANCER CELLS

3,4-(Methylenedioxy)-1-(2',3'-epoxypropyl)-benzene (safrole oxide) was synthesized in the authors' laboratory. To investigate the effects of safrole oxide on the growth and apoptosis of A549 human lung cancer cells, the authors treated the cells with safrole oxide, 112.36 to 449.44 micromol/L, for 24 to 48 hours. The results showed that the drug led A549 cells to apoptosis and blocked cell cycle completely at G1 phase and partly at G(2)-M phase. To further study the correlated mechanism, the authors examined P53 and H-Ras protein expressions by using immunofluorescence assay. They found that the expression of P53 was dramatically up-regulated but the expression of H-Ras was hardly affected by safrole oxide, 224.72 micromol/L, within 24 hours. Taken together, these results revealed that safrole oxide could induce apoptosis of A549 cells and suggested that safrole oxide might perform its function by blocking cells completely at G1 phase and partly at G(2)-M phase, and also by up-regulating the expression of P53 protein. These findings would raise exciting possibilities for cancer therapy in future.

CD3zeta expression and T cell proliferation are inhibited by TGF-beta1 and IL-10 in cervical cancer patients

INTRODUCTION

Cervical cancer development from a squamous intraepithelial lesion is thought to be favored by an impaired T cell immunity. We evaluated parameters of T cell alterations such as proliferation, cytokine, and CD3zeta expression in peripheral blood and tumor-infiltrating T lymphocytes from women with squamous intraepithelial lesions (SIL) or cervical cancer (CC).

RESULTS AND DISCUSSION

T cell proliferation and cytokine messenger RNA (mRNA) expression were similar in women with SIL and healthy donors, whereas low T cell proliferation and lower mRNA expression of IL-2, IL-10 and IFN-gamma were observed in women with CC. Moreover, infiltrating cells showed marginal responses. We also found that CD3zeta mRNA expression, whose protein is required for T cell activation, correlated with a decreased proliferation in advanced stages of the disease.

CONCLUSION

Experiments with T cells from healthy donors in the presence TGF-beta1 or IL-10 suggest that these cytokines have a relevant role in T cell responses during CC progression.

Novel morpholin-3-one derivatives induced apoptosis and elevated the level of P53 and Fas in A549 lung cancer cells

Previously, we found that nine kinds of new morpholin-3-one derivatives could inhibit the growth of A549 lung cancer cells in a dose-dependent manner, but how they performed their function remained unknown. In this paper, we studied the effects of the three more effective morpholin-3-one derivatives {4-(4-chlorophenyl)-6-((4-nitrophenoxy) methyl) morpholin-3-one (1); 6-(4-chlorophenoxy)-4-(4-methoxyphenyl) morpholin-3-one (2); and 6-((4-nitrophenoxy) methyl)-4-phenylmorpholin-3-one (3)} on the cell cycle distribution, apoptosis, and the level of P53 and Fas that are two kinds of important proteins in the regulation of A549 cell growth and apoptosis. According to the results of cell viability, we selected 40 microg/ml of morpholin-3-one derivatives as the most appropriate concentration for the following study. The results showed that the morpholin-3-one derivatives partly blocked the cells at G1 phase, induced apoptosis, and elevated the level of P53 and Fas proteins significantly. The effect of the morpholin-3-one derivates was associated with translocation of P53 and clustering of Fas. Our data suggested that the morpholin-3-one derivates might be promising tools for elucidating the molecular mechanism of lung cancer cell apoptosis and they will be very potential candidates for developing anti-cancer drugs.

Studies on anti-tumour activities of pseudolaric acid-B (PLAB) and its mechanism of action

Pseudolaric acid-B (PLAB), a diterpene acid, was isolated from the root and trunk barks of Pseudolarix kaempferi. It showed antifungal and anti-fertility effects as well as cytotoxic activities in previous studies. The present study investigates cytotoxic activity on cultured human cancer cells, inhibition on the growth of transplantable tumours in mice and the mechanism of these actions. The experimental results showed that PLAB had potent cytotoxic effects on cancer cells derived from different tissues. MTT assay showed that its IC50 towards these tumour cells was 0.17 to 5.20 micromol/L, and towards one normal human kidney proximal tubular epithelial cell (HKC) was 5.77 micromol/L. Furthermore, the results of cell growth curve and colony formation of cancer cells matched the above results. The results in vivo demonstrated that PLAB significantly inhibited the growth of transplantable tumours, such as Lewis lung cancer and hepatocarcinoma 22 (H22) in mice. The inhibitory rate to H22 was 14.4% and 40.1%, and to Lewis lung cancer reached 39.1% and 47.0%, when PLAB was given by intraperitoneal injection (i.p.) at a dose of 30 mg/kg/day and 60 mg/kg/day for 10 days, respectively. It is suggested that PLAB also showed obvious anticancer activity in vivo. Inducing apoptosis by PLAB in HeLa cells was assessed by various morphological and biochemical characteristics, including cell shrinkage, chromatin condensation, membrane blebbing, formation of apoptotic bodies, and internucleosomal DNA fragmentation. A typical 'sub-G1 peak' was also checked through flow cytometry. These results were accompanied by up-regulating P53, down-regulating Bcl-2 and activating Caspase-3, which was revealed by Western blotting. PLAB also caused cell cycle arrest to G2/M phase in a dose-dependent manner. The experiments suggest that PLAB is a new potent anti-tumour agent.

Bcl-2-mediated potentiation of neocarzinostatin-induced apoptosis: requirement for caspase-3, sulfhydryl groups, and cleavable Bcl-2

Overexpression of antiapoptotic Bcl-2 family members is thought to contribute to chemotherapeutic resistance of neural crest tumors. Paradoxical potentiation by Bcl-2 of apoptosis induced by the antineoplastic prodrug, neocarzinostatin (NCS), has been observed in PC12 pheochromocytoma cells. Prior studies have indicated that the cleavage of Bcl-2 to its proapoptotic counterpart mediated by caspase-3 is responsible for this potentiation of apoptosis. This has led to the hypothesis that induction of caspase-3 expression in bcl-2-transfected, caspase-3-deficient MCF-7 cells, will result in Bcl-2 cleavage and Bcl-2-dependent potentiation of NCS-induced apoptosis. These studies have further led to the hypothesis that both cleavable Bcl-2 and sulfhydryl groups are required for the activity of caspase-3 in this regard. As hypothesized, co-transfection of bcl-2-transfected MCF-7 cells with a caspase-3 expression construct results in cleavage of Bcl-2 and potentiation of dose-dependent, NCS-mediated cell death. Furthermore, PC12 cells transfected with an expression construct for cleavage-resistant Bcl-2 demonstrated attenuated potentiation of apoptosis relative to their counterparts transfected with wild-type bcl-2. Finally, irreversible oxidative titration of sulfhydryl groups resulted in concentration-dependent attenuation of apoptosis in PC12 cells, along with prevention of caspase-3 activation and Bcl-2 cleavage. These results definitively demonstrate the requirement for caspase-3, cleavable Bcl-2, and available sulfhydryl groups (separate from those required for NCS activation) in potentiation of NCS-induced apoptosis by Bcl-2.