TP53 codon 72 polymorphism and risk of conjunctival squamous cell carcinoma in Uganda

Histologic and Genomic Analysis of Conjunctival SCC in African and American Cohorts Reveal UV Light and HPV Signatures and High Tumor Mutation Burden

Purpose

Conjunctival squamous cell carcinoma (conjSCC) is more prevalent and aggressive in sub-Saharan African countries compared with the rest of the world. This study aims to compare the genomic, immunophenotypic, and histologic features between patients from the United States and Ethiopia, to identify etiopathogenic mechanisms and unveil potential treatment strategies.

Methods

We compared histologic features and mutational profiles using whole exome sequencing, high-risk human papillomavirus (HPV) status, PD-L1 expression, and tumor-infiltrating lymphocytes in conjSCC tumors of patients from Ethiopia (ETH; n = 25) and the United States (from MD Anderson [the MDA cohort]; n = 29). Genomic alterations were compared with SCCs from other anatomic sites using data from The Cancer Genome Atlas.

Results

Solar elastosis was seen in 78% of ETH and 10% of MDA samples. Thicker tumors had higher density of CD8+ and CD3+ cells. HPV status was similar between the cohorts (ETH = 21% and MDA = 28%). The mean tumor mutation burden (TMB) was significantly higher in conjSCC (3.01/Mb, log10) and cutaneous SCC compared other SCC subtypes. ETH samples had higher TMB compared to the MDA cohort (3.34 vs. 2.73). Mutations in genes associated with ultraviolet light (UV) signature were most frequently encountered (SBS7b = 74% and SBS7a = 72%), with higher prevalence in the ETH cohort, whereas SBS2 and SBS13 signatures were more common among MDA HPV+ conjSCCs.

Conclusions

Our findings suggest that UV exposure may play a major role in conjSCC, with a higher prevalence in the ETH cohort compared with the MDA cohort, where HPV also contributes.

Genetic predisposition to ocular surface disorders and opportunities for gene-based therapies

The ocular surface, comprised of the corneal and conjunctival epithelium, innervation system, immune components, and tear-film apparatus, plays a key role in ocular integrity as well as comfort and vision. Gene defects may result in congenital ocular or systemic disorders with prominent ocular surface involvement. Examples include epithelial corneal dystrophies, aniridia, ectrodactyly-ectodermal dysplasia-clefting (EEC) syndrome, xeroderma pigmentosum (XP), and hereditary sensory and autonomic neuropathy. In addition, genetic factors may interact with environmental risk factors in the development of several multifactorial ocular surface disorders (OSDs) such as autoimmune disorders, allergies, neoplasms, and dry eye disease. Advanced gene-based technologies have already been introduced in disease modelling and proof-of-concept gene therapies for monogenic OSDs. For instance, patient-derived induced pluripotent stem cells have been used for modelling aniridia-associated keratopathy (AAK), XP, and EEC syndrome. Moreover, CRISPR/Cas9 genome editing has been used for disease modelling and/or gene therapy for AAK and Meesmann's epithelial corneal dystrophy. A better understanding of the role of genetic factors in OSDs may be helpful in designing personalized disease models and treatment approaches. Gene-based approaches in monogenic OSDs and genetic predisposition to multifactorial OSDs such as immune-mediated disorders and neoplasms with known or possible genetic risk factors has been seldom reviewed. In this narrative review, we discuss the role of genetic factors in monogenic and multifactorial OSDs and potential opportunities for gene therapy.

Stratifin in ocular surface squamous neoplasia and its association with p53

PURPOSE

Sunlight-induced p53 mutations are known to contribute towards increased risk of ocular surface squamous neoplasia (OSSN). Stratifin (14-3-3σ)/HEM (human epithelial marker) is a p53-mediated inhibitor of cell cycle progression and has been shown to be a target of epigenetic deregulation in various carcinomas. In the present study, Stratifin expression, its promoter methylation status as well as expression of mutant p53 in early and advanced AJCC stages (8th edition) of OSSN, was evaluated.

METHODS

Sixty-four OSSN [20 conjunctival intraepithelial neoplasia (CIN) and 44 squamous cell carcinoma (SCC)] patients were registered for this study, and they were followed up for 36-58 months (mean 48 ± 3.6). Immunoexpression of Stratifin and mutant p53 protein, mRNA expression of Stratifin by reverse transcription polymerase chain reaction (PCR) and methylation status of Stratifin by methylation-specific PCR, was undertaken.

RESULTS

Hypermethylation of Stratifin promoter in 63% (40/64), loss of Stratifin expression in 75% (48/64) and downregulation of Stratifin mRNA in 61% (39/64) were observed. Stratifin hypermethylation was significantly associated with reduced disease-free survival in both early and advanced T stage SCC cases. Expression of mutant p53 expression was seen in 48% (31/64) OSSN cases. Of the 31 patients with mutant p53 expression, 87% (27/31) also demonstrated loss of Stratifin immunoexpression. A significant association was seen between mutant p53 expression and Stratifin loss (p = 0.01) in advanced T stage SCC cases.

CONCLUSIONS

Hypermethylation of Stratifin gene and its reduced mRNA expression both are potential biomarkers for identifying high-risk OSSN patients. Aberrant methylation of Stratifin and simultaneous mutant p53 expression implicates involvement of p53-Stratifin mediated signalling pathway in the pathogenesis of OSSN.

Conjunctival squamous intraepithelial neoplasia and its differential diagnosis

Conjunctival squamous intraepithelial neoplasia (CSIN) represents the in situ precursor of squamous cell carcinoma. The graded severity of intraepithelial dysplasia is considered a measure of risk for progression to invasive carcinoma. The range of cytoarchitectural changes in CSIN overlaps those of reactive atypia, squamous epithelial papilloma and in situ sebaceous carcinoma. Pseudoepitheliomatous hyperplasia and benign hereditary dyskeratosis of the conjunctiva are conditions without risk of neoplastic transform that are potentially mistaken for CSIN.

Observational study of ocular surface squamous neoplasia: Risk factors, diagnosis, management and outcomes at a tertiary eye hospital in South Africa

BACKGROUND

Ocular surface squamous neoplasia (OSSN) is the most common ocular surface tumour. Diagnosis and management have traditionally been by excision biopsy. Recently there has been success with the use of topical chemo or immunotherapy, which has resulted in a move from invasive diagnosis by histology to an array of non-invasive diagnostic tests.

METHODS

This observational study aims to describe the characteristics of patients with OSSN at St John Eye Hospital in Johannesburg, South Africa. Non-invasive diagnostic tests (impression cytology, anterior segment-OCT, methylene blue staining) will be compared to the gold standard, histology. Treatment success, recurrence and adverse events will be documented between three treatment options that include: surgical excision, topical 5-Fluorouracil (5FU) chemotherapy, and topical 5FU with retinoic acid therapy.

DISCUSSION

There is a trend to the use of less invasive diagnosis and management for OSSN. Minimally invasive diagnostic tests include cytology, anterior-segment OCT and methylene blue staining. The study will compare these to the gold standard histology, thereby providing evidence for their use in clinical practice. Interferon alpha 2b is commonly used as immunotherapy for OSSN. The cost of this medication is prohibitive to its adoption in a developing country. We therefore decided to use 5FU as the chemotherapeutic agent of choice in this study. The success, adverse events and recurrence rates with this agent may provide additional evidence for its use in the management of OSSN. Overall, if diagnosis and management can be implemented with good success in the outpatient environment, care can be improved for this condition in a developing country.

Genetic variants association with cancers in African-based populations: A systematic review

BACKGROUND

Cancer is the single leading cause of human deaths worldwide. The highest incidence and mortality are recorded from Africa. The last two decades have witnessed extensive research which has led to emerging prognosis and new gene therapy technologies. Cancer therapy in Africa is derived with little input from African population data. While a number of cancer studies on African populations have suggested varied susceptible variant, no comprehensive review of these studies has been undertaken to assess their coverage across Africa.

METHODS

This study aimed to undertake a review of all molecular genetic studies that interrogated the genetic variants of cancers in African-based populations. Our search methodology was modelled after the Cochrane systematic review protocol, which included MeSH terms and related keywords.

RESULTS

Ninety-seven articles studying 13 cancer types, were reviewed. 91 articles screened for polymorphisms using PCR-based techniques while three used SNP array, two used whole exome sequencing and one used pyrosequencing. North African (NA) countries undertook 51/97 (53 %) studies on 12/13 (92 %) cancer types while the Sub Saharan Africa (SSA) countries undertook 46/97 (47 %) studies on 7/13 (54 %) cancer types. Twelve out of these thirteen cancer type studies suggested susceptibility to their target polymorphism (p > 0.05). No study replicated or validated variants detected.

CONCLUSION

Research on genetic determinants in African-based population cancer offers translational benefits. We recommended large scale, multi-national genome association studies using high throughput techniques. SSA needs to receive more attention due to the shortage of this type of study and data in the region.

Telomerase promoter mutations in human immunodeficiency virus-related conjunctiva neoplasia

BACKGROUND

Squamous cell carcinoma (SCC) of the conjunctiva is a common cancer in Africa mainly associated with solar ultraviolet (UV) exposure and human immunodeficiency virus (HIV) infection. We analyzed the role of HIV on the occurrence of telomerase reverse transcriptase (TERT) promoter mutations among a cohort of conjunctiva neoplasia Ugandan patients.

METHODS

Telomerase reverse transcriptase promoter mutations were searched in 72 conjunctiva neoplasia cases, comprising SCC and intraepithelial neoplasia grade 1-3 (CIN1-3), as well as in 53 conjunctiva normal tissues and in 24 HIV-related Kaposi sarcoma.

RESULTS

The average prevalence of TERT promoter mutations in conjunctiva neoplasia was 31.9%. The mutation rates were significantly higher in HIV-positive (31.8% of CIN1 and CIN2, 46.2% of CIN3 and SCC,) than HIV-negative patients (22.2% of CIN1 and CIN2, 13.3% of CIN3 and SCC). Such mutations were rarely identified among HIV-positive conjunctiva controls (3.6%) and never in Kaposi sarcoma lesions. The most frequent variations were the hot spots - 124G>A and - 146G>A and tandem transitions - 124_125GG>AA and - 138_139GG>AA.

CONCLUSIONS

Telomerase reverse transcriptase promoter mutations are early events in conjunctival neoplasia and could be used for timely diagnosis of conjunctiva tumours. The high frequency of UV-signatures in HIV-positive conjunctiva lesions suggests an additive effect of the virus to UV-related mutagenesis.

Identification of Human Herpesvirus 8 Sequences in Conjunctiva Intraepithelial Neoplasia and Squamous Cell Carcinoma of Ugandan Patients

The incidence of squamous cell carcinoma of the conjunctiva is particularly high in sub-Saharan Africa with temporal trends similar to those of Kaposi sarcoma (KS). Human herpesvirus type 8 (HHV8), has not yet been investigated in conjunctiva tumors. In this study biopsies and PBMCs of conjunctiva neoplasia patients along with nonneoplastic conjunctiva tissues have been analyzed for HHV8 sequences by PCR targeting ORF26. All amplimers were subjected to nucleotide sequencing followed by phylogenetic analysis. HHV8 DNA has been identified in 12 out of 48 (25%) HIV-positive, and in 2 out of 24 (8.3%) HIV-negative conjunctiva neoplastic tissues and in 4 out of 33 (12.1%) PBMC samples from conjunctiva neoplasia diseased patients as well as in 4 out of 60 (6.7%) nontumor conjunctiva tissues. The viral load ranged from 1 to 400 copies/10⁵ cells. Phylogenetic analysis showed that the majority of HHV8 ORF26 amplimers clustered with subtypes R (n = 11) and B2 (n = 6). This variant distribution is in agreement with that of HHV8 variants previously identified in Ugandan KS cases. The presence of HHV8 in conjunctiva tumors from HIV-positive patients warrants further studies to test whether HHV8 products released by infected cells may have paracrine effects on the growth of conjunctiva lesions.

High twinning rate in Cândido Godói: a new role for p53 in human fertility

BACKGROUND

Cândido Godói (CG) is a small town in South Brazil, which has the highest prevalence of twin births in Brazil. Recently, a number of studies have shown that p53 plays an important role in reproduction through blastocyst implantation and intra utero embryo survival. Thus, gene polymorphisms in the p53 pathway were investigated in this population.

METHODS

Single nucleotide polymorphisms from five genes in the p53 pathway were investigated, as well as background characteristics of 42 mothers of twins (cases) and 101 mothers of singletons (controls), all residents from CG.

RESULTS

Mothers of twins have higher number of pregnancies and higher frequencies of P72 allele at TP53 and T allele at MDM4 genes compared with controls. Logistic regression shows that both TP53 and number of pregnancies maintained their association with twinning (P =0.004 and P =0.002, respectively), with TP53 having a higher odds ratio than number of pregnancies (2.73 versus 1.70, respectively). No interactive effect between TP53 and MDM4 (P =0.966) is observed. As expected, mothers of twins have three times more cases of cancer in their first-degree relatives than control mothers (P =0.011).

CONCLUSIONS

Our results suggest that the P72 allele of TP53 is a strong risk factor for twinning in CG, while the number of pregnancies and the T allele at MDM4 may represent weaker risk factors. These two alleles are associated with infertility, but the anti-apoptotic effect of low levels of p53 in general, and of the P72 allele in particular, may play a role after implantation, enhancing the chance for a double pregnancy to succeed to term.

MDM2 and CDKN1A gene polymorphisms and risk of Kaposi's sarcoma in African and Caucasian patients

A single-nucleotide polymorphism in the MDM2 promoter (SNP309; rs2279744) causes elevated transcription of this major negative regulator of p53 in several cancer types. We investigated MDM2 SNP309 and CDKN1A (p21/Waf1/Cip1) codon 31 (rs1801270) polymorphisms in 86 cases of cutaneous Kaposi's sarcoma (KS) from African and Caucasian patients, and 210 healthy controls. A significant increase of the MDM2 SNP309 T/G genotype was observed among classic KS cases (odds ratio 2.38, 95% confidence interval 1.0-5.5). Frequencies of CDKN1A codon 31 genotypes were not significantly different between cases and controls. The results suggest that the MDM2 SNP309 G allele may act as a susceptibility gene for the development of classic KS in Caucasian patients.

Genital and cutaneous human papillomavirus (HPV) types in relation to conjunctival squamous cell neoplasia: a case-control study in Uganda

BACKGROUND

We investigated the role of infection with genital and cutaneous human papillomavirus types (HPV) in the aetiology of ocular surface squamous neoplasia (which includes both conjunctival intraepithelial neoplasia (CIN) and carcinoma) using data and biological material collected as part of a case-control study in Uganda.

RESULTS

Among 81 cases, the prevalence of genital and cutaneous HPV types in tumour tissue did not differ significantly by histological grade of the lesion. The prevalence of genital HPV types did not differ significantly between cases and controls (both 38%; Odds ratio [OR] 1.0, 95% confidence interval [CI] 0.4-2.7, p = 1.0). The prevalence of cutaneous HPV types was 22% (18/81) among cases and 3% (1/29) among controls (OR 8.0, 95% CI 1.0-169, p = 0.04).

CONCLUSION

We find no evidence of an association between genital HPV types and ocular surface squamous neoplasia. The prevalence of cutaneous HPV was significantly higher among cases as compared to controls. Although consistent with results from two other case-control studies, the relatively low prevalence of cutaneous HPV types among cases (which does not differ by histological grade of tumour) indicates that there remains considerable uncertainty about a role for cutaneous HPV in the aetiology of this tumour.

Genetic studies of African populations: an overview on disease susceptibility and response to vaccines and therapeutics

Africa is the ultimate source of modern humans and as such harbors more genetic variation than any other continent. For this reason, studies of the patterns of genetic variation in African populations are crucial to understanding how genes affect phenotypic variation, including disease predisposition. In addition, the patterns of extant genetic variation in Africa are important for understanding how genetic variation affects infectious diseases that are a major problem in Africa, such as malaria, tuberculosis, schistosomiasis, and HIV/AIDS. Therefore, elucidating the role that genetic susceptibility to infectious diseases plays is critical to improving the health of people in Africa. It is also of note that recent and ongoing social and cultural changes in sub-Saharan Africa have increased the prevalence of non-communicable diseases that will also require genetic analyses to improve disease prevention and treatment. In this review we give special attention to many of the past and ongoing studies, emphasizing those in Sub-Saharan Africans that address the role of genetic variation in human disease.

The growing problem of non-AIDS-defining malignancies in HIV

PURPOSE OF REVIEW

The incidence and spectrum of non-AIDS-defining cancers has continued to grow. As HIV-infected individuals live longer due to highly active antiretroviral therapy, their risk of dying from one of these cancers is increased. The recent literature pertaining to non-AIDS-defining cancers is reviewed.

RECENT FINDINGS

Recent epidemiological studies have identified higher rates of carcinoma of the anus, lung, breast, skin, conjunctiva, liver and prostate; hematopoietic malignancies such as Hodgkin's lymphoma, plasma-cell neoplasia and leukemia; and other neoplasms like melanoma and leiomyosarcoma in HIV-positive patients. The role of HIV-induced immunosuppression in the development of these non-AIDS-defining cancers appears less important than lifestyle habits like smoking and sun exposure, as well as coinfection with human papilloma, hepatitis B, hepatitis C and Epstein-Barr viruses.

SUMMARY

It is unclear whether the growing number of reports on non-AIDS-defining cancers reflects a true increased incidence or merely the product of increased surveillance, detection and reporting. Highly active antiretroviral therapy not only promotes longevity in the HIV-positive population, but may increase their risk of developing cancer like Hodgkin's lymphoma. Assertive prevention strategies are needed to adequately deal with non-AIDS-defining cancers in an aging and growing HIV-positive population.

Challenges and opportunities for treatment and research of AIDS-related malignancies in Africa

PURPOSE OF REVIEW

Following our review of AIDS-associated cancer in developing nations in 2004, we sought to update recent publications and review data on the challenges and opportunities for the treatment and research of AIDS malignancies in Africa.

RECENT FINDINGS

It is apparent that the burden of AIDS-related malignancies and other virus-associated tumors is significant and increasing in Africa. Several recent studies report findings on conjunctival squamous cell carcinoma and there is a report that Hodgkin's disease, a non-AIDS-defining neoplasm, is increasing in incidence. International collaborative partnerships dedicated to AIDS malignancies in developing countries are feasible and invaluable for clinical strategies to address this aspect of the pandemic. A departure point is the ongoing work of the East Africa - Case Western Reserve University Collaboration in AIDS malignancies.

SUMMARY

The burden of neoplastic complications of HIV infection and endemic virus-associated tumors are assuming increasing significance in Africa. There is a need to develop nonmyelotoxic therapies and approaches that are hypothesis-driven and pathogenesis-based. The scarcity and shortages in this region demand that our scientific and therapeutic strategies are both suitable and pragmatic for testing in this setting. It is also imperative that African investigators lead us in this important endeavor.