HPV induced cervical carcinogenesis: molecular basis and vaccine development

TSPAN1: A Novel Protein Involved in Head and Neck Squamous Cell Carcinoma Chemoresistance

Simple Summary

Therapy resistance in head and neck squamous cell carcinoma (HNSCC) patients is the main obstacle to achieve more effective treatments that improve survival and quality of life of these patients. Therefore, it is of vital importance to unravel the molecular and cellular mechanisms by which tumor cells acquire resistance to chemotherapy. We conducted a comparative proteomic study involving cisplatin-resistant cells and cancer stem cells with the aim of identifying proteins potentially implicated in the acquisition of cisplatin resistance. Through this study, we identified for the first time tetraspanin-1 (TSPAN1) as an important protein involved in the development, progression and chemoresistance of HNSCC tumors.

Abstract

Sensitization of resistant cells and cancer stem cells (CSCs) represents a major challenge in cancer therapy. A proteomic study revealed tetraspanin-1 (TSPAN1) as a protein involved in acquisition of cisplatin (CDDP) resistance (Data are available via ProteomeXchange with identifier PXD020159). TSPAN1 was found to increase in CDDP-resistant cells, CSCs and biopsies from head and neck squamous cell carcinoma (HNSCC) patients. TSPAN1 depletion in parental and CDDP-resistant HNSCC cells reduced cell proliferation, induced apoptosis, decreased autophagy, sensitized to chemotherapeutic agents and inhibited several signaling cascades, with phospho-SRC inhibition being a major common target. Moreover, TSPAN1 depletion in vivo decreased the size and proliferation of parental and CDDP-resistant tumors and reduced metastatic spreading. Notably, CDDP-resistant tumors showed epithelial–mesenchymal transition (EMT) features that disappeared upon TSPAN1 inhibition, suggesting a link of TSPAN1 with EMT and metastasis. Immunohistochemical analysis of HNSCC specimens further revealed that TSPAN1 expression was correlated with phospho-SRC (pSRC), and inversely with E-cadherin, thus reinforcing TSPAN1 association with EMT. Overall, TSPAN1 emerges as a novel oncogenic protein and a promising target for HNSCC therapy.

Characterization of NOL7 gene point mutations, promoter methylation, and protein expression in cervical cancer

NOL7 is a putative tumor suppressor gene localized to 6p23, a region with frequent loss of heterozygosity in a number of cancers, including cervical cancer (CC). We have previously demonstrated that reintroduction of NOL7 into CC cells altered the angiogenic phenotype and suppressed tumor growth in vivo by 95%. Therefore, to understand its mechanism of inactivation in CC, we investigated the genetic and epigenetic regulation of NOL7. NOL7 mRNA and protein levels were assessed in 13 CC cell lines and 23 consecutive CC specimens by real-time quantitative polymerase chain reaction, western blotting, and immunohistochemistry. Methylation of the NOL7 promoter was analyzed by bisulfite sequencing and mutations were identified through direct sequencing. A CpG island with multiple CpG dinucleotides spanned the 5' untranslated region and first exon of NOL7. However, bisulfite sequencing failed to identify persistent sites of methylation. Mutational sequencing revealed that 40% of the CC specimens and 31% of the CC cell lines harbored somatic mutations that may affect the in vivo function of NOL7. Endogenous NOL7 mRNA and protein expression in CC cell lines were significantly decreased in 46% of the CC cell lines. Finally, immunohistochemistry demonstrated strong NOL7 nucleolar staining in normal tissues that decreased with histologic progression toward CC. NOL7 is inactivated in CC in accordance with the Knudson 2-hit hypothesis through loss of heterozygosity and mutation. Together with evidence of its in vivo tumor suppression, these data support the hypothesis that NOL7 is the legitimate tumor suppressor gene located on 6p23.

Identification and characterization of the human NOL7 gene promoter

NOL7 is a candidate tumor suppressor gene that localizes to 6p23, a chromosomal region frequently associated with loss of heterozygosity in a number of malignancies including cervical cancer (CC). Re-expression of NOL7 in CC cells suppresses in vivo tumor growth by 95% and alters the angiogenic phenotype by modulating the expression of VEGF and TSP1. Here, we describe the determination of two NOL7 transcriptional start sites (TSS), the cloning of its regulatory promoter region, and the identification of transcription factors that regulate its expression. Using 5' Rapid amplification of complementary DNA ends (RACE), two transcriptional start sites were identified. Deletion analysis determined that the essential elements required for the optimal promoter activity of NOL7 were 560 bp upstream of its translation start site. In silico analysis suggested that the promoter region contained potential binding sites for the SP1, c-Myc and RXRalpha transcription factors as well as an overall GC content of greater than 60%. Chromatin immunoprecipitation (ChIP) confirmed that SP1, c-Myc and RXRalpha bound to the NOL7 promoter region. Finally, we demonstrate that NOL7 expression was positively regulated by c-Myc and RXRalpha. These results demonstrate that the NOL7 promoter region possesses each of the key elements of a TATA-less promoter. In addition, the positive regulation of NOL7 by c-Myc and RXRalpha provides additional mechanistic insights into the potential role of NOL7 in CC and other malignancies.

Impact of a quadrivalent HPV6/11/16/18 vaccine in Mexican women: public health implications for the region

BACKGROUND AND AIMS

Recognition of human papillomavirus (HPV) as a necessary cause of cervical cancer (CC) led to new perspectives for its control and the demonstration of an effective primary prevention strategy through vaccination. We undertook this study to evaluate the safety, efficacy and immunogenicity of a quadrivalent HPV6/11/16/18 vaccine in Mexican women.

METHODS

A total of 679 Mexican women between 18 and 23 years old participated in two Phase III double-blind, randomized, placebo-controlled clinical trials of a quadrivalent HPV 6/11/16/18 vaccine. Women were enrolled who tested negative for pregnancy and reported having four or less sexual partners during their lifetime. Vaccine or placebo was administered at day 1, month 2 and month 6.

RESULTS

Among Mexican women who were naïve to the respective vaccine type at enrollment, the quadrivalent vaccine was highly efficacious, preventing 100% of HPV6/11/16/18-related cervical intraepithelial neoplasia grade 2/3, adenocarcinoma in situ, condyloma and vaginal intraepithelial neoplasia. Statistical significance was not reached for every endpoint due to the limited sample size. Vaccination was generally well tolerated and immunogenic.

DISCUSSION

To widely administer the vaccine, collaborative efforts should be coordinated among public, private and local community sectors. In light of the scarce knowledge of many health professionals with respect to the primary prevention of CC, it will be necessary to educate health providers on the advantages and specific recommendations of HPV vaccines and secondary prevention. Decision making should be based on scientific evidence, allowing health professionals to provide an organized social response that supports the universal right to health.

Role of senescence and mitotic catastrophe in cancer therapy

Senescence and mitotic catastrophe (MC) are two distinct crucial non-apoptotic mechanisms, often triggered in cancer cells and tissues in response to anti-cancer drugs. Chemotherapeuticals and myriad other factors induce cell eradication via these routes. While senescence drives the cells to a state of quiescence, MC drives the cells towards death during the course of mitosis. The senescent phenotype distinguishes tumor cells that survived drug exposure but lost the ability to form colonies from those that recover and proliferate after treatment. Although senescent cells do not proliferate, they are metabolically active and may secrete proteins with potential tumor-promoting activities. The other anti-proliferative response of tumor cells is MC that is a form of cell death that results from abnormal mitosis and leads to the formation of interphase cells with multiple micronuclei. Different classes of cytotoxic agents induce MC, but the pathways of abnormal mitosis differ depending on the nature of the inducer and the status of cell-cycle checkpoints. In this review, we compare the two pathways and mention that they are activated to curb the growth of tumors. Altogether, we have highlighted the possibilities of the use of senescence targeting drugs, mitotic kinases and anti-mitotic agents in fabricating novel strategies in cancer control.

Cataracts in transgenic mice caused by a human papillomavirus type 18 E7 oncogene driven by KRT1-14

Human papillomavirus type 18 (HPV18) is a common cause of cervical cancer. To create a mouse model for this common neoplastic disease, we used a human keratin 14 promoter to drive the HPV18 E7 oncogene to create transgenic mice. No mice up to a year of age developed cervical cancer. However, all transgenic mice and none of the controls developed progressive bilateral cortical cataracts. By 6 months of age, the cortex liquefied leaving the lens nucleus. Proliferation of lens epithelium formed multifocal nodules and free floating lens epithelial cells within the liquefied cortex. These cells were hyperplastic not neoplastic. Other HPV transgenic stocks develop cataracts suggesting this virus may have a broad cellular tropism.

Molecular cytogenetic characterization of human papillomavirus16-transformed foreskin keratinocyte cell line 16-MT

Anogenital cancers are closely associated with human papillomavirus (HPV), and HPV-infected individuals, particularly those with high-grade dysplasias, are at increased risk for cervical and anal cancers. Although genomic instability has been documented in HPV-infected keratinocytes, the full spectrum of genetic changes in HPV-associated lesions has not been fully defined. To address this, we examined an HPV16-transformed foreskin keratinocyte cell line, 16-MT, by GTG-banding, spectral karyotyping (SKY), and array comparative genomic hybridization (array CGH); these analyses revealed multiple numerical, complex, and cryptic chromosome rearrangements. Based on GTG-banding, the 16-MT karyotype was interpreted as 78-83,XXY,+add(1)(p36.3),+3,+4,+5,+5,+7,+8,+i(8)(q10)x2,+10,?der(12),der(13;14)(q10;q10),+15,+16,add(19)(q13.3),+21,+21,-22[cp20]. Multicolor analysis by SKY confirmed and further characterized the anomalies identified by GTG banding. The add(1) was identified as a der(1)(1qter-->1q25::1p36.1-->1qter), the add(19) as a dup(19), and the der(12) interpreted as a der(11) involving a duplication of chromosome 11 material and rearrangement with chromosome 19. In addition, previously unidentified der(9)t(9;22), der(3)t(3;19), and der(4)t(4;9) were noted. The 16-MT cell line showed losses and gains of DNA due to unbalanced translocations and complex rearrangements of regions containing known tumor suppressor genes. Chromosomal changes in these regions might explain the increased risk of cancer associated with HPV. Also, array CGH detected copy-number gains or amplifications of chromosomes 2, 8, 10, and 11 and deletions of chromosomes 3, 4, 11, and 15. These results provide the basis for the identification of candidate oncogenes responsible for cervical and anal cancer in amplified regions, and for putative tumor suppressor genes in commonly deleted regions like 11q22-23. Furthermore, these data represent the first full characterization of the HPV-positive cell line 16-MT.

Prophylactic human papillomavirus vaccines: the beginning of the end of cervical cancer

Persistent infection with one of the oncogenic human papillomavirus (HPV) types is a necessity for the development of cervical cancer. By HPV vaccination, cervical cancer could become a very rare disease. Two types of HPV vaccines can be distinguished: (i) therapeutic vaccines which induce cellular immunity targeted against epithelial cells infected with HPV and (ii) prophylactic vaccines inducing virus-neutralizing antibodies protecting against new but not against established infections. At present, several vaccines have been developed and tested in clinical trials. The vaccines are generally well tolerated and highly immunogenic. The current clinical data indicate that prophylactic vaccines are very effective against new persistent infections and the development of cervical intraepithelial lesions. The protection is type specific. However, the follow-up of the vaccination trials is still short. The effect of HPV vaccines on future cancer incidence will only be known after decades of follow-up. This article will address the status of recently terminated phase II and currently running phase III trials with prophylactic HPV vaccines.

Vaccination strategies for the treatment and prevention of cervical cancer

PURPOSE OF REVIEW

Immunotherapy of HPV-induced premalignant anogenital lesions and cervical cancer has made impressive progress. HPV as causative agent is targeted by prophylactic and therapeutic vaccination strategies. Preclinical and clinical studies have shown induction of natural and/or vaccine-induced immune responses. This review will summarize the status of vaccine development and clinical testing published since March 2003.

RECENT FINDINGS

For prophylactic vaccines there is first clinical evidence of effectivity (ie, 100% protection from HPV infection and dysplasia by virus-like particle (VLP) vaccine-induced neutralizing antibodies). Also, therapeutic vaccines have entered clinical evaluation. While prophylactic VLP vaccines are immunogenic per se, therapeutic vaccines will need further adjuvants to guide T cell differentiation, expansion, survival, and homing to tumor sites. To enhance clinical outcome of successful T cell induction in patients, the susceptibility of the tumor cells for lysis must be addressed in the future, since tumor immune evasion is a severe problem in cervical cancer.

SUMMARY

While successful prophylactic HPV vaccines have entered large clinical trials, therapeutic HPV vaccines, in spite of T cell induction, lack clinical responses due to the problem of tumor immune evasion. Adjuvants for systemic and local immune modulation will be mandatory for effective therapy.