Antiviral activity of Cidofovir on a naturally human papillomavirus-16 infected squamous cell carcinoma of the head and neck (SCCHN) cell line improves radiation sensitivity

Targeted Therapy as a Potential De-Escalation Strategy in Locally Advanced HPV-Associated Oropharyngeal Cancer: A Literature Review

The treatment landscape of locally advanced HPV-oropharyngeal squamous cell carcinoma (OPSCC) is undergoing transformation. This is because the high cures rates observed in OPSCC are paired with severe treatment-related, long-term toxicities. These significant adverse effects have led some to conclude that the current standard of care is over-treating patients, and that de-intensifying the regimens may achieve comparable survival outcomes with lower toxicities. Consequently, several de-escalation approaches involving locally advanced OPSCC are underway. These include the reduction of dosage and volume of intensive cytotoxic regimens, as well as elimination of invasive surgical procedures. Such de-intensifying treatments have the potential to achieve efficacy and concurrently alleviate morbidity. Targeted therapies, given their overall safer toxicity profiles, also make excellent candidates for de-escalation, either alone or alongside standard treatments. However, their role in these endeavors is currently limited, because few targeted therapies are currently in clinical use for head and neck cancers. Unfortunately, cetuximab, the only FDA-approved targeted therapy, has shown inferior outcomes when paired with radiation as compared to cisplatin, the standard radio-sensitizer, in recent de-escalation trials. These findings indicate the need for a better understanding of OPSCC biology in the design of rational therapeutic strategies and the development of novel, OPSCC-targeted therapies that are safe and can improve the therapeutic index of standard therapies. In this review, we summarize ongoing research on mechanism-based inhibitors in OPSCC, beginning with the salient molecular features that modulate tumorigenic processes and response, then exploring pharmacological inhibition and pre-clinical validation studies of candidate targeted agents, and finally, summarizing the progression of those candidates in the clinic.

Phase I trial evaluating the antiviral agent Cidofovir in combination with chemoradiation in cervical cancer patients

Purpose

This phase I trial aimed to assess the safety and determine the recommended Phase II dose (RP2D) of Cidofovir combined with chemoradiotherapy in patients with stage IB2-IVA cervical cancer.

Experimental design

Incremental doses (1, 2.5, 5 and 6.5 mg/kg) of IV Cidofovir were administered weekly for two weeks, and then every 2 weeks from the start of chemoradiotherapy to the initiation of utero-vaginal brachytherapy. Biological expression of HPV was analyzed during treatment and tumor response was assessed according to RECIST v1.0 criteria.

Results

A total of 15 patients were treated with Cidofovir. Dose-limiting toxicities occurred in 2/6 patients at the 6.5 mg/kg dose level (G3 proteinuria, and G3 acute pyelonephritis with G3 febrile neutropenia). No toxicity occurred at the 5 mg/kg dose level, but only 3 patients received this dose due to trial interruption because of low accrual. The most frequent G3-4 adverse effects observed during the trial were: abdominal pain (n=3), infection (n=2), leuckoneutropenia (n=2), and others (n=6). No toxic death or major renal side effect occurred. The best response was that 8/9 evaluable patients achieved a complete response (89%). In the intention to treat population, the 2-year overall and progression-free survival rates were 93% and 76%, respectively. Biological monitoring of HPV-related markers (decreased p16 expression, and increased p53 and pRb levels) was possible on sequential tumor biopsy samples. The genomic alterations identified were PIK3CA (n=5; one also had a KRAS mutation), and HRAS (n=1) mutations.

Conclusion

Cidofovir at a dose of 5mg/kg combined with chemoradiotherapy appeared tolerable and yielded tumor regressions. Due to early trial interruption, the RP2D was not confirmed.

The broad-spectrum anti-DNA virus agent cidofovir inhibits lung metastasis of virus-independent, FGF2-driven tumors

The FDA-approved anti-DNA virus agent cidofovir (CDV) is being evaluated in phase II/III clinical trials for the treatment of human papillomavirus (HPV)-associated tumors. However, previous observations had shown that CDV also inhibits the growth of vascular tumors induced by fibroblast growth factor-2 (FGF2)-transformed FGF2-T-MAE cells. Here, we demonstrate that CDV inhibits metastasis induced by FGF2-driven, virus-independent tumor cells. Pre-treatment of luciferase-expressing FGF2-T-MAE cells with CDV reduced single cell survival and anchorage-independent growth in vitro and lung metastasis formation upon intravenous inoculation into SCID mice. This occurred in the absence of any effect on homing of FGF2-T-MAE cells to the lungs and on the growth of subconfluent cell cultures or subcutaneous tumors in mice. Accordingly, CDV protected against lung metastasis when given systemically after tumor cell injection. Lung metastases in CDV-treated mice showed reduced Ki67 expression and increased nuclear accumulation of p53, indicating that CDV inhibits metastasis by affecting single cell survival properties. The anti-metastatic potential of CDV was confirmed on B16-F10 melanoma cells, both in zebrafish embryos and mice. These findings suggest that CDV may have therapeutic potential as an anti-metastatic agent and warrants further study to select those tumor types that are most likely to benefit from CDV therapy.

De-escalation of radiation dose for human papillomavirus-positive oropharyngeal head and neck squamous cell carcinoma: A case report and preclinical and clinical literature review

Traditionally, head and neck squamous cell carcinoma (HNSCC) has been considered to be a relatively homogeneous disease. However, recent data have demonstrated that human papillomavirus (HPV)-positive and HPV-negative disease are two different clinical entities associated with different outcomes. Preclinical and clinical studies have reported a divergence in treatment strategies as well as prognostic outcomes for HNSCCs that are HPV-positive versus HPV-negative. The present study describes the case of a 52-year-old man who presented with stage IVB cT2N3M0 right tonsillar HPV-positive squamous cell carcinoma. Induction chemotherapy with docetaxel, cisplatin and 5-fluorouracil (TPF), followed by chemoradiation therapy with carboplatin and 70 Gray (Gy) radiation in daily fractions was recommended. The patient completed the TPF and carboplatin treatment; however, he was unable to tolerate the radiation course, receiving a final dose of 46 Gy. A 60-day follow-up right neck salvage dissection was subsequently performed. Despite having received a partial radiation treatment of 46 Gy, the patient had no pathological evidence of disease at 60 days post radiation treatment. Repeat positron emission tomography-computed tomography at 32 months after the right neck dissection revealed no evidence of disease. The present study also discusses the current preclinical in vitro and in vivo targets for HPV-positive HNSCC and the obstacles presented in advancing clinical treatment modalities. Previous preclinical models investigating radiation sensitivity have yielded mixed results. Thus, it is important to understand and establish representative preclinical models for studying HPV and HNSCC to improve clinical research and therapeutic development. This review may guide future understanding of the role of HPV in HNSCC.

Increased radiosensitivity of HPV-positive head and neck cancers: Molecular basis and therapeutic perspectives

Human papillomavirus driven head and neck squamous cell carcinoma (HNSCC), particularly oropharyngeal squamous cell carcinoma (OPSCC), are characterized by a significant survival advantage over their HPV-negative counterparts. Although the reasons behind this are still not fully elucidated, it is widely accepted that these tumors have a higher response to ionizing radiation that might explain their favorable outcomes. Potential underlying intrinsic mechanisms include impaired DNA repair abilities, differences in activated repopulation-signaling pathways and cell cycle control mechanisms. The role of the microenvironment is increasingly highlighted, particularly tumor oxygenation and the immune response. Recent studies have shown a distinct pattern of intratumoral immune cell infiltrates, according to HPV status, and have suggested that an increased cytotoxic T-cell based antitumor immune response is involved in improved prognosis of patients with HPV-positive OPSCC. These significant milestones, in the understanding of HPV-induced HNSCC, pave the way to new therapeutic opportunities. This article reviews the current evidence on the biological basis of increased radiosensitivity in HPV-positive HNSCC and discusses potential therapeutic implications.

Emerging drugs for the treatment of cervical cancer

INTRODUCTION

Worldwide, most cervical cancer (CC) patients require the use of drug therapy either adjuvant, concurrent with radiation or palliative.

AREAS COVERED

This review briefly discusses the current achievements in treating CC with an emphasis in emerging agents.

EXPERT OPINION

Concurrent cisplatin with radiation and lately, gemcitabine-cisplatin chemoradiation has resulted in small but significant improvements in the treatment of locally advanced and high-risk early-stage patients. So far, only antiangiogenic therapy with bevacizumab added to cisplatin chemoradiation has demonstrated safety and encouraging results in a Phase II study. In advanced disease, cisplatin doublets yield median survival rates not exceeding 14 months. The first Phase III study of bevacizumab, added to standard chemotherapy cisplatin- or non-cisplatin-containing doublet, has shown significant increase in both overall survival and progression-free survival. Further studies are needed before bevacizumab plus chemotherapy can be considered the standard of care for advanced disease. The characterization of the mutational landscape of CC and developments of novel targeted therapies may result in more effective and individualized treatments for CC. The potential efficacy of knocking down the key alterations in CC, E6 and E7 human papilloma virus oncoproteins must not be overlooked.

New molecular targets against cervical cancer

Cervical cancer is the third most commonly diagnosed cancer worldwide and the fourth leading cause of cancer death in women. Major advances but still insufficient achievements in the treatment of locally advanced and high-risk early stage patients have occurred in the last decade with the incorporation of concurrent cisplatin with radiation and, lately, gemcitabine added to cisplatin chemoradiation. Despite a number of clinical studies incorporating molecular-targeted therapy as radiosensitizers being in progress, so far, only antiangiogenic therapy with bevacizumab added to cisplatin chemoradiation has demonstrated safety and shown encouraging results in a Phase II study. In advanced disease, cisplatin doublets do not have a great impact on the natural history of the disease with median survival rates not exceeding 13 months. The first Phase III study of bevacizumab, added to cisplatin or a non-cisplatin-containing doublet, showed significant increase in both overall survival and progression-free survival. Further studies are needed before bevacizumab plus chemotherapy can be considered the standard of care for advanced disease. Characterization of the mutational landscape of cervical cancer has already been initiated, indicating that, for now, few of these targetable alterations match with available agents. Progress in both the mutational landscape knowledge and developments of novel targeted therapies may result in more effective and individualized treatments for cervical cancer. The potential efficacy of knocking down the key alterations in cervical cancer – E6 and E7 human papillomavirus oncoproteins – must not be overlooked.

The combination of the antiviral agent cidofovir and anti-EGFR antibody cetuximab exerts an antiproliferative effect on HPV-positive cervical cancer cell lines' in-vitro and in-vivo xenografts

Cervical carcinoma remains a leading cause of female mortality worldwide and over 90% of these tumors contain the human papillomavirus (HPV) genome. Cross-talk between the epidermal growth factor receptor and HPV has been reported and is implicated in tumor progression. The combination of the antiviral compound cidofovir (Cd) with the monoclonal antibody antiepidermal growth factor receptor cetuximab (Cx) was evaluated. HPV-positive (HeLa and Me180) and HPV-negative (C33A, H460 and A549) human cancer cell lines were incubated with Cd (1-10 μg/ml) and/or Cx (10 or 50 μg/ml). The antitumor effect of the combination was assessed in vitro using a clonogenic survival assay, cell cycle analysis, and phospho-H2AX level. Tumor growth delay was assayed in vivo using xenograft models. A pan-genomic analysis was carried out to identify the genes expressed differentially in untreated HeLa HPV-positive cells versus cells treated by the Cd-Cx combination. The Cd-Cx combination inhibited proliferation in all the cell lines tested. The association of Cd and Cx exerted a synergistic activity on HPV-positive but not on HPV-negative cell lines. The combination delayed tumor growth of HPV-positive tumors in vivo; however, no efficacy was reported on HPV-negative C33A xenografts nor on cell lines treated by single-drug therapy. The combination induced an S-phase arrest associated with an enhanced level of the double-strand break in Me180 and HeLa cell lines. Gene profiling assays showed a significant differential modulation of genes in HeLa cell lines treated with the combination involving the EGR-1 transcription factor. The current data support a synergistic antiproliferative action of the Cd-Cx combination on HPV-related cervical tumors.

Cidofovir: a novel antitumor agent for glioblastoma

PURPOSE

Cidofovir (CDV) is an U.S. Food and Drug Administration (FDA)-approved nucleoside antiviral agent used to treat severe human cytomegalovirus (HCMV) infection. Until now, no clear therapeutic effects of CDV have been reported outside of the setting of viral infection, including a potential role for CDV as an antineoplastic agent for the treatment of brain tumors.

EXPERIMENTAL DESIGN

We investigated the cytotoxicity of CDV against the glioblastoma cells, U87MG and primary SF7796, both in vitro and in vivo, using an intracranial xenograft model. Standard techniques for cell culturing, immunohistochemistry, Western blotting, and real-time PCR were employed. The survival of athymic mice (n = 8-10 per group) bearing glioblastoma tumors, treated with CDV alone or in combination with radiation, was analyzed by the Kaplan-Meier method and evaluated with a two-sided log-rank test.

RESULTS

CDV possesses potent antineoplastic activity against HCMV-infected glioblastoma cells. This activity is associated with the inhibition of HCMV gene expression and with activation of cellular apoptosis. Surprisingly, we also determined that CDV induces glioblastoma cell death in the absence of HCMV infection. CDV is incorporated into tumor cell DNA, which promotes double-stranded DNA breaks and induces apoptosis. In the setting of ionizing radiotherapy, the standard of care for glioblastoma in humans, CDV augments radiation-induced DNA damage and, further, promotes tumor cell death. Combination therapy with CDV and radiotherapy significantly extended the survival of mice bearing intracranial glioblastoma tumors.

CONCLUSION

We have identified a novel antiglioma property of the FDA-approved drug CDV, which heightens the cytotoxic effect of radiotherapy, the standard of care therapy for glioblastoma.

Cidofovir selectivity is based on the different response of normal and cancer cells to DNA damage

Background

Cidofovir (CDV) proved efficacious in treatment of human papillomaviruses (HPVs) hyperplasias. Antiproliferative effects of CDV have been associated with apoptosis induction, S-phase accumulation, and increased levels of tumor suppressor proteins. However, the molecular mechanisms for the selectivity and antitumor activity of CDV against HPV-transformed cells remain unexplained.

Methods

We evaluated CDV drug metabolism and incorporation into cellular DNA, in addition to whole genome gene expression profiling by means of microarrays in two HPV⁺ cervical carcinoma cells, HPV^- immortalized keratinocytes, and normal keratinocytes.

Results

Determination of the metabolism and drug incorporation of CDV into genomic DNA demonstrated a higher rate of drug incorporation in HPV⁺ tumor cells and immortalized keratinocytes compared to normal keratinocytes. Gene expression profiling clearly showed distinct and specific drug effects in the cell types investigated. Although an effect on inflammatory response was seen in all cell types, different pathways were identified in normal keratinocytes compared to immortalized keratinocytes and HPV⁺ tumor cells. Notably, Rho GTPase pathways, LXR/RXR pathways, and acute phase response signaling were exclusively activated in immortalized cells. CDV exposed normal keratinocytes displayed activated cell cycle regulation upon DNA damage signaling to allow DNA repair via homologous recombination, resulting in genomic stability and survival. Although CDV induced cell cycle arrest in HPV^- immortalized cells, DNA repair was not activated in these cells. In contrast, HPV⁺ cells lacked cell cycle regulation, leading to genomic instability and eventually apoptosis.

Conclusions

Taken together, our data provide novel insights into the mechanism of action of CDV and its selectivity for HPV-transformed cells. The proposed mechanism suggests that this selectivity is based on the inability of HPV⁺ cells to respond to DNA damage, rather than on a direct anti-HPV effect. Since cell cycle control is deregulated by the viral oncoproteins E6 and E7 in HPV⁺ cells, these cells are more susceptible to DNA damage than normal keratinocytes. Our findings underline the therapeutic potential of CDV for HPV-associated malignancies as well as other neoplasias.

Primary chemotherapy and radiation as a treatment strategy for HPV-positive oropharyngeal cancer

The incidence of human papillomavirus-positive oropharyngeal cancer (HPV/OPSCC) is rapidly increasing, which will represent a major public health burden for decades to come. Although HPV/OPSCC is generally associated with a better prognosis than HPV-negative OPSCC, the survival rate of individuals with higher-risk clinical and pathologic features remains unchanged. Emerging evidence suggests that HPV/OPSCC is pathologically and molecularly distinct from HPV-negative OPSCC. This review focuses on summarizing treatment strategies for HPV/OPSCC by reviewing the peer-reviewed literature and noting ongoing and planned clinical trials in this disease. We also discuss the potential of designing targeted therapy based on the recent genomic findings of HPV/OPSCC.

Molecular markers for cancer prognosis and treatment: have we struck gold?

The last decade has witnessed an emerging role for molecular or biochemical markers indicating a specific cellular mechanism or tissue function, often called 'biomarkers'. Biomarkers such as altered DNA, proteins and inflammatory cytokines are critical in cancer research and strategizing treatment in the clinic. In this review we look at the application of biological indicators to cancer research and highlight their roles in cancer detection and treatment. With technological advances in gene expression, genomic and proteomic analysis, biomarker discovery is expanding fast. We focus on some of the predominantly used markers in different types of malignancies, their advantages, and their limitations. Finally we conclude by looking at the future of biomarkers, their utility in the tumorigenic studies, and the progress towards personalized treatment strategies.

Next-generation treatment strategies for human papillomavirus-related head and neck squamous cell carcinoma: where do we go?

Oncogenic human papillomavirus (HPV) is currently recognised as a major risk factor for the development of head and neck squamous cell carcinomas (HNSCC). HPV is mostly detected in tumours arising from the oropharynx and more specifically from the tonsil. HPV-related tumours display clinical and molecular characteristics that are distinct from HPV-unrelated tumours, which are generally induced by alcohol and tobacco abuse. Detection of biologically active HPV in HNSCC has prognostic relevance, which warrants the separate classification of HPV-induced tumours and is a prerequisite for further optimisation of treatment protocols for this distinct group. Current guidelines for the treatment of oropharyngeal squamous cell carcinoma (OPSCC) have not incorporated specific treatment modalities for HPV-related tumours. The development of such treatment options is still in a preclinical phase or in early clinical trials. Recent data on treatment response of OPSCC have been obtained by retrospectively analysing HPV-status and indicate that patients with HPV-related tumours show a favourable prognosis, independent of the type of treatment. These patients may benefit from de-intensified treatment, which should be assessed in prospective clinical trials. The development and future use of new antiviral and immunomodulatory therapeutics may be instrumental in this approach to improve survival rates and decrease disease-and-treatment-related morbidity. In this review we will focus on present therapeutic HPV-targeting strategies and discuss future directions for de-intensified treatment of HPV-positive HNSCC.

Yet another ten stories on antiviral drug discovery (part D): paradigms, paradoxes, and paraductions

This review article presents the fourth part (part D) in the series of stories on antiviral drug discovery. The stories told in part D focus on: (i) the cyclotriazadisulfonamide compounds; (ii) the {5-[(4-bromophenylmethyl]-2-phenyl-5H-imidazo[4,5-c]pyridine} compounds; (iii) (1H,3H-thiazolo[3,4-a]benzimidazole) derivatives; (iv) T-705 (6-fluoro-3-hydroxy-2-pyrazinecarboxamide) and (v) its structurally closely related analogue pyrazine 2-carboxamide (pyrazinamide); (vi) new strategies for the treatment of hemorrhagic fever virus infections, including, as the most imminent, (vii) dengue fever, (viii) the veterinary use of acyclic nucleoside phosphonates; (ix) the potential (off-label) use of cidofovir in the treatment of papillomatosis, particularly RRP (recurrent respiratory papillomatosis); and (x) finally, the prophylactic use of tenofovir to prevent HIV infections.

Potential risk factors associated with the use of cidofovir to treat benign human papillomavirus-related disease

BACKGROUND

Cidofovir is currently being used off-licence to treat different viral infections, such as benign low-risk human papillomavirus (HPV)-related recurrent respiratory papillomatosis (RRP). There are concerns over the safety of this practice as rat studies demonstrated a high malignant transformation rate. As yet, there are no clinical reports of cidofovir-induced malignant changes in humans.

METHODS

Telomerase immortalised human keratinocytes (hTert) stably expressing E6 proteins from either low-risk HPV6b or high-risk HPV16 and vector control cells were treated with either low-dose (5 microg/ml) or higher dose (30 microg/ml) cidofovir for 2 days and the effects evaluated by clonogenic survival assays. Based on these results, gene expression microarray analysis was performed on cidofovir-treated low-risk E6 and vector cells before, during and after drug treatment, and the results verified by real-time PCR.

RESULTS

Both low-risk and high-risk E6-expressing cells show significantly improved long-term survival compared with vector control cells when exposed to 5 microg/ml cidofovir for 2 days, (hTert T6E6 P=0.0007, hTert T16E6 P=0.00023 and hTert vector control P=0.62). Microarray and real-time PCR analyses of low-dose cidofovir-treated low-risk E6-expressing cells revealed changes in gene expression that are known to be associated with malignant progression, which were not observed in drug-treated vector control cells.

CONCLUSIONS

This is the first report that cidofovir can both increase cell survival and induce alterations in gene expression that are known to be associated with malignant transformation in cells transduced only with the E6 gene from low-risk HPV. It is our belief that these data provide cause for concern over the off-license use of this drug to treat RRP.

Cidofovir induces an increase in levels of low-risk and high-risk HPV E6

BACKGROUND

Cidofovir is a nucleoside analogue that is used off-license to treat recurrent respiratory papillomatosis (RRP) caused by HPV6/11. However, the effect of this drug upon low-risk HPV 6/11 gene expression is unknown.

METHODS

The expression of E6 was evaluated by RT-PCR in HPV-ve C33A cervical carcinoma cells stably transfected with both low- and high-risk HPV E6 cDNA's and in SiHa (HPV16+ve) cervical carcinoma cells after treatment with 2 doses and durations of exposure to cidofovir.

RESULTS

Compared to the vector only transcript, E6 RNA levels showed an 8-fold increase in low-risk and 20-fold increase in high-risk E6-expressing cells. High-risk E6 protein levels were also detected by Western blot in cidofovir-treated C33A Type16 E6-transfected cells.

CONCLUSION

These data may indicate a potential rationale for increased risk of genetic instability and thus transformation due to drug-induced increase in the level of E6.

Novel anti-metastatic action of cidofovir mediated by inhibition of E6/E7, CXCR4 and Rho/ROCK signaling in HPV tumor cells

Cervical cancer is frequently associated with HPV infection. The expression of E6 and E7 HPV oncoproteins is a key factor in its carcinogenicity and might also influence its virulence, including metastatic conversion. The cellular mechanisms involved in metastatic spread remain elusive, but pro-adhesive receptors and their ligands, such as SDF-1α and CXCR4 are implicated. In the present study, we assessed the possible relationship between SDF-1α/CXCR4 signaling, E6/E7 status and the metastatic process. We found that SDF-1α stimulated the invasion of E6/E7-positive cancer cell lines (HeLa and TC-1) in Matrigel though CXCR4 and subsequent Rho/ROCK activation. In pulmonary metastatic foci generated by TC-1 cells IV injection a high proportion of cells expressed membrane-associated CXCR4. In both cases models (in vitro and in vivo) cell adhesion and invasion was abrogated by CXCR4 immunological blockade supporting a contribution of SDF-1α/CXCR4 to the metastatic process. E6 and E7 silencing using stable knock-down and the approved anti-viral agent, Cidofovir decreased CXCR4 gene expression as well as both, constitutive and SDF-1α-induced cell invasion. In addition, Cidofovir inhibited lung metastasis (both adhesion and invasion) supporting contribution of E6 and E7 oncoproteins to the metastatic process. Finally, potential signals activated downstream SDF-1α/CXCR4 and involved in lung homing of E6/E7-expressing tumor cells were investigated. The contribution of the Rho/ROCK pathway was suggested by the inhibitory effect triggered by Cidofovir and further confirmed using Y-27632 (a small molecule ROCK inhibitor). These data suggest a novel and highly translatable therapeutic approach to cervix cancer, by inhibition of adhesion and invasion of circulating HPV-positive tumor cells, using Cidofovir and/or ROCK inhibition.

Scientific and clinical aspects of the use of cidofovir in recurrent respiratory papillomatosis

OBJECTIVE

Cidofovir is the most contemporary adjuvant treatment for recurrent respiratory papillomatosis (RRP) and its use is increasing. Cidofovir is potentially harmful. Otolaryngologists should understand the science of cidofovir and review the current published data on the effects of this therapy.

METHOD

Pubmed was searched using the terms cidofovir and papillomatosis. Comparisons were made between published articles.

RESULTS

Thirteen articles were identified between 1998 and 2006, representing the treatment of 142 patients. Cidofovir did result in a significant improvement of papillomatous lesions in the majority (60%) of patients despite the use of different regimes of cidofovir administration. There was no unifying protocol in use. A partial response was demonstrated in 29% of patients. 7.5% had no response however, an additional 3.5% patients were lost to follow-up. No malignant change was reported.

CONCLUSION

Cidofovir does appear to be effective in improving the outcome of patients with RRP. There are no reports of malignant transformation despite concerns raised by toxicology studies.

Cell-permeable artificial zinc-finger proteins as potent antiviral drugs for human papillomaviruses

Human papillomavirus (HPV) is one of the important pharmaceutical targets because infection of the high-risk types causes invasive cervical cancer. However, effective antiviral drugs for HPV have not been developed so far. In the present study, we constructed cell-permeable artificial zinc-finger proteins (AZPs) by fusing an AZP previously generated for inhibition of HPV-18 DNA replication with a cell-penetrating peptide (CPP) as candidates for new antiviral drugs against HPV. We confirmed that these CPP-AZP fusions reduced the replication rate in transient replication assays when added to the culture medium. In particular, 250 nM CPP-AZP (designated AZP-R9) containing a 9-mer of arginine as the CPP reduced HPV-18 DNA replication to 3% of that of a control, and the 50% effective concentration (EC50) was <31 nM. Furthermore, a cytotoxicity assay revealed that the 50% inhibitory concentration (IC50) of AZP-R9 was >10 microM. Therefore, the selectivity index, defined as IC50/EC50, was >300, which is better than that of the antiviral cidofovir for HPVs. Thus, our results demonstrate that cell-permeable AZPs could serve as potent protein-based antiviral drugs.

Effects of cidofovir on a novel cell-based test system for recurrent respiratory papillomatosis

BACKGROUND

Cidofovir has been reported to have activity against human papillomavirus (HPV) type 16, but no laboratory studies have been performed on HPV type 6, the main cause of recurrent respiratory papillomatosis (RRP).

METHODS

HPV6b E6 cDNA-based C33A (non-HPV cervical carcinoma) cell line was produced. Two different doses of cidofovir were applied to parent C33A, C33AT6E6, and C33AT16E6 (HPV 16). Growth and flow cytometry analysis were performed.

RESULTS

Polymerase chain reaction confirmed HPV6 E6 expression in C33AT6E6 cells. High-dose cidofovir was found to be toxic to all cell lines. Low-dose exposure was found to be toxic to C33AT16E6 cells at 3 days, whereas C33A and C33AT6E6 showed minimal toxicity at 6 days and earlier recovery following drug withdrawal.

CONCLUSIONS

Cidofovir showed nonspecific toxicity against all 3 cell lines tested. HPV16 E6 expressing cells were more sensitive than parent or HPV6 E6 expressing cells. Cidofovir has no selective advantage for the RRP-related HPV6 E6 expressing cell line.

Cidofovir administered with radiation displays an antiangiogenic effect mediated by E6 inhibition and subsequent TP53-dependent VEGF repression in HPV18+ cell lines

Therapeutic administration of the antiviral agent cidofovir with radiation markedly enhanced the antitumor effect of ionizing radiation in cells of two HPV18+ human cervical carcinoma cell lines. Although this potent radiosensitizing effect was associated with repression of the viral oncoproteins E6/ E7 and restoration of TP53 as shown previously, additional mechanisms may be involved. In the present study, we investigated the antiangiogenic effect of the combination of cidofovir and radiation in cells of two HPV18+ cervical cancer cell lines, HeLa and ME180, and assessed the molecular mechanisms associated with the antiangiogenic effect observed. Cells were exposed to cidofovir (10 microg/ml) and irradiated (1-9 Gy). The angiogenic response was studied in vitro by a matrigel invasion assay. Modulations of E6, TP53 and VEGF mRNA and protein levels were studied by real-time RT-PCR, Western blot analysis and ELISA, respectively. Then a double RNA interference approach was used to analyze the connection between E6/TP53 and VEGF. The combination of cidofovir and radiation had a potent antiangiogenic effect. It induced E6 inhibition, restoration of TP53, and reduction of the proangiogenic phenotype of HPV18+ cells associated with VEGF inhibition. A siRNA strategy showed an anti-VEGF action of the combination mediated directly by E6 inhibition and TP53 restoration, since E6 siRNA inhibited VEGF whereas co-transfection with E6 and TP53 siRNA abrogated the anti-VEGF effect. This study showed that the combination of cidofovir with ionizing radiation has an antiangiogenic effect associated with VEGF inhibition subsequent to E6 inhibition and TP53 restoration.

The influence of clinical and demographic risk factors on the establishment of head and neck squamous cell carcinoma cell lines

The purpose of this study was to generate stable cell cultures from head and neck squamous cell carcinomas (HNSCC), and retrospectively analyze the factors associated with successful cell line establishment. Fifty-two HNSCC cell lines were isolated from a series of 199 tumors collected between 1992 and 1997 at the University of Pittsburgh Medical Center. Cell lines were characterized at the molecular and cellular level to determine the features associated with cell line formation. Successful cell line formation was dependent on multiple factors, including gene amplification involving chromosomal band 11q13, local and/or regional involvement of lymph nodes, and alcohol usage. The establishment of HNSCC cell lines enriches the resources available for cancer research. Our findings indicate that generation of stable cell lines from HNSCC is biased towards tumors with a poor prognosis. Our 52 stable lines comprise one of the largest series of HNSCC cell lines in the literature, with complete demographic, histopathologic, clinical, and survival data.