The role of occupation and a past history of malaria in the etiology of classic Kaposi's sarcoma: a case-control study in north-east Sardinia

Puzzling and ambivalent roles of malarial infections in cancer development and progression

Scientific evidence strongly suggests that parasites are directly or indirectly associated with carcinogenesis in humans. However, studies have also indicated that parasites or their products might confer resistance to tumour growth.Plasmodiumprotozoa, the causative agents of malaria, exemplify the ambivalent link between parasites and cancer. Positive relationships between malaria and virus-associated cancers are relatively well-documented; for example, malaria can reactivate the Epstein-Barr Virus, which is the known cause of endemic Burkitt lymphoma. Nevertheless, possible anti-tumour properties of malaria have also been reported and, interestingly, this disease has long been thought to be beneficial to patients suffering from cancers. Current knowledge of the potential pro- and anti-cancer roles of malaria suggests that, contrary to other eukaryotic parasites affecting humans,Plasmodium-related cancers are principally lymphoproliferative disorders and attributable to virus reactivation, whereas, similar to other eukaryotic parasites, the anti-tumour effects of malaria are primarily associated with carcinomas and certain sarcomas. Moreover, malarial infection significantly suppresses murine cancer growth by inducing both innate and specific adaptive anti-tumour responses. This review aims to present an update regarding the ambivalent association between malaria and cancer, and further studies may open future pathways to develop novel strategies for anti-cancer therapies.

Kaposi sarcoma and quinine: a potentially overlooked triggering factor in millions of Africans

Kaposi sarcoma (KS)-associated herpesvirus, also known as human herpesvirus 8, is necessary but not sufficient for the development of KS. Lytic reactivation of human herpesvirus 8 may be important in KS pathogenesis. KS and its causative agent, KS-associated herpesvirus, have distinctive largely unexplained geographic distributions. We note the recent "oncoweed" hypothesis of biologic plants in the environment accounting for this reactivation. We believe that quinine and its derivatives might better explain the epidemiology of KS than oncoweeds. Indeed, we propose an "oncodrug" hypothesis, specifically with regard to quinine and its derivatives, a linkage first advanced by one of us (V. R.) and associates in 1984.

Risk of classic Kaposi sarcoma with exposures to plants and soils in Sicily

Background

Ecologic and in vitro studies suggest that exposures to plants or soil may influence risk of Kaposi sarcoma (KS).

Methods

In a population-based study of Sicily, we analyzed data on contact with 20 plants and residential exposure to 17 soils reported by 122 classic KS cases and 840 sex- and age-matched controls. With 88 KS-associated herpesvirus (KSHV) seropositive controls as the referent group, novel correlates of KS risk were sought, along with factors distinguishing seronegatives, in multinomial logistic regression models that included matching variables and known KS cofactors - smoking, cortisone use, and diabetes history. All plants were summed for cumulative exposure. Factor and cluster analyses were used to obtain scores and groups, respectively. Individual plants and soils in three levels of exposure with P_trend ≤ 0.15 were retained in a backward elimination regression model.

Results

Adjusted for known cofactors, KS was not related to cumulative exposures to 20 plants [per quartile adjusted odds ratio (OR_adj) 0.96, 95% confidence interval (CI) 0.73 - 1.25, P_trend = 0.87], nor was it related to any factor scores or cluster of plants (P = 0.11 to 0.81). In the elimination regression model, KS risk was associated with five plants (P_trend = 0.02 to 0.10) and with residential exposure to six soils (P_trend = 0.01 to 0.13), including three soils (eutric regosol, chromic/pellic vertisol) used to cultivate durum wheat. None of the KS-associated plants and only one soil was also associated with KSHV serostatus. Diabetes was associated with KSHV seronegativity (OR_adj 4.69, 95% CI 1.97 - 11.17), but the plant and soil associations had little effect on previous findings that KS risk was elevated for diabetics (OR_adj 7.47, 95% CI 3.04 - 18.35) and lower for current and former smokers (OR_adj 0.26 and 0.47, respectively, P_trend = 0.05).

Conclusions

KS risk was associated with exposure to a few plants and soils, but these may merely be due to chance. Study of the effects of durum wheat, which was previously associated with cKS, may be warranted.

Distribution of 'promoter' sandflies associated with incidence of classic Kaposi's sarcoma

The patchy geographical distributions of classic Kaposi's sarcoma (KS) and human herpesvirus type 8 (HHV-8), better known as Kaposi's sarcoma-associated herpesvirus (KSHV) remain unexplained. It has been proposed that certain species of bloodsucking insects ('promoter arthropods') promote the reactivation of HHV-8/KSHV and facilitate both HHV-8/KSHV transmission and KS development. This hypothesis was tested by sampling the presence and density of human-biting Diptera with CDC light traps in two areas of Sardinia with contrasting incidence rates of classic KS. In total, 11,030 specimens (99.9% sandflies and 0.1% mosquitoes) belonging to 10 species were collected from 40 rural sites. Five of these species are considered to be possible promoter arthropods because of the irritation their bites cause: Phlebotomus perniciosus Newstead; Phlebotomus perfiliewi Parrot (Diptera: Psychodidae); Aedes berlandi Seguy; Culiseta annulata (Schrank) and Culex theileri Theobald (Diptera: Culicidae). Five species are probable 'non-promoters' because their bites are not particularly irritating: Culiseta longiareolata (Macquart); Culex pipiens s.l.; Anopheles algeriensis Theobald; Anopheles maculipennis s.l., and Anopheles plumbeus Stephens. A significant correlation was found between the geographical distribution of promoter arthropods and incidence rates of KS (Spearman's r = 0.59,P < 0.01). Promoter arthropods were more likely to be caught in areas with cutaneous leishmaniasis and a past high prevalence of malaria, and in areas of limestone, acid volcanic soil and cereal cultivation. The study supports the association between promoter arthropods and classic KS, which may explain the geographic variability of KS and HHV-8/KSHV, and highlights the links with a number of variables previously associated with the incidence of KS.

Kaposi sarcoma: a continuing conundrum

Kaposi sarcoma (KS) remains a challenge. Its classic or Mediterranean form tends to be benign. In transplant recipients it may be less so. As part of the AIDS pandemic, of which it was an original defining component, it may be life-threatening. It is due to human herpesvirus-8, which is necessary but not sufficient to produce the disease. KS has a low prevalence in the general population of the United States and United Kingdom, with an intermediate rate in Italy and Greece, and a high one in parts of Africa. In Italy, hot spots include its southern regions, the Po River Valley, and Sardinia, possibly related to a high density of blood-sucking insects. An important challenge is to treat KS patients without immunocompromising them. The potential of effective anti-herpes virus therapy and the use of sirolimus in transplantation recipients have added new opportunities for KS prevention.

LEARNING OBJECTIVES

At the conclusion of this learning activity, participants should be able to provide the most recent information about Kaposi sarcoma in the context in which it occurs. Its classic or Mediterranean form, its pattern in transplant recipients and others iatrogenically immunosuppressed, and its occurrence as a potentially life-threatening part of the AIDS pandemic will be stressed. Its etiology and transmission will be discussed in detail to facilitate understanding of Kaposi sarcoma and of human herpesvirus-8 infection in the general population of the United States and United Kingdom, in Italy and Greece, and in certain parts of Africa. Its therapy, including the concept of doing it without immunocompromising the patient, will be stressed. New opportunities for Kaposi sarcoma prevention will also be discussed.

Classic Kaposi sarcoma in northern Sardinia: A prospective epidemiologic overview (1977-2003) correlated with malaria prevalence (1934)

BACKGROUND

Studies have demonstrated considerable variations in classic Kaposi sarcoma (CKS) incidence within Europe, with some of the highest incidences found in the Mediterranean area. As a Mediterranean area, northern Sardinia has a high CKS frequency.

OBJECTIVE

In order to determine CKS incidence in people born in and residing in northern Sardinia, a clinical prospective epidemiologic study was carried out between 1977 and 2003 by the Department of Dermatology, University of Sassari. We also evaluated a correlation between malaria prevalence in 1934, estimated on the eight historical sub-areas of the Sassari province, and the standardized morbidity ratio from 1977 to 2003.

RESULTS

A total of 332 patients with CKS were identified. Incidence among the northern Sardinian population > or =40 years of age was 4.06/100,000 persons/year and it was almost stable through the years. The male to female ratio showed a significant decline from 3.6 to 2.5 (P = .03). Females had a statistically decreased risk of developing CKS compared to males (adjusted incidence rate ratio = 0.27; 95% CI: 0.21-0.34), and the risk of developing CKS increased exponentially with age. The prevalence of malaria in each sub-area ranged from 9% to 91%. The standardized morbidity ratio for CKS in the years between 1977 and 2003 ranged from 0.27 to 1.76; the regression coefficient was -0.85 (95% CI: -2.94-1.24), yielding a nonsignificant relationship between the two diseases.

LIMITATIONS

These results were obtained from patients with CKS in northern Sardinia and may not be applicable to other populations.

CONCLUSIONS

The northern Sardinian population consistently has a very high incidence of CKS, while in our data, the correlation between malaria and CKS remains open to question.

Epidemiological and clinical characteristics of classic Kaposi's sarcoma in Peru

BACKGROUND

Classic Kaposi sarcoma (KS) occurs predominantly among the elderly, with predominance among Jews, Italians, and Greeks. Classic KS has been seen relatively frequently in Peru.

OBJECTIVE

Our purpose was to outline the epidemiological and clinical profile of classic KS in Peru.

METHODS

Epidemiological and clinical features of all classic KS cases diagnosed between 1969 and 2003 at Hospital Nacional Cayetano Heredia (HNCH) and between 1946 and 2004 at Instituto Nacional de Enfermedades Neoplasicas (INEN) were reviewed and studied retrospectively.

RESULTS

An overall incidence of 2.54 per 10,000 attended patients was obtained at the INEN during the 48-year period (mean, 2.39; standard deviation: 1.99; 95% confidence interval, 2.92-1.86). Twenty-one cases were discovered at HNCH and 106 cases at INEN. A male/female ratio of 2.62:1 was found. Mean age at diagnosis was 68.5 years. Lower limbs were involved in 109 patients (85.8%); the trunk was involved in 11 patients (8.6%). Nodules were the most common type of lesion (85.8%); less commonly found were plaques (27.5%), macules (12.5%), papules (12.5%), and ulcers (8.6%). Sixty-two patients had no symptoms (48.8%). Pain was the most common symptom (26.7%), followed by edema (21.2%), bleeding (14.9%), and pruritus (3.9%). A second primary malignancy was found in 11 patients (8.6%).

LIMITATIONS

These results were obtained from patients with classic KS in Peru and may not be applicable to other populations.

CONCLUSION

Classic KS is quite common in Peru with sporadic cases found throughout the country and some clustering in the coastal region. Classic KS in Peru has a clinical presentation that is very similar, but not identical, to the classic KS described in the Mediterranean region, exhibiting some special clinical and epidemiological characteristics with a nodular, nonsymmetric presentation that usually affects the lower extremities.

Classic Kaposi's sarcoma in southern Sardinia, Italy

The first examination of classical Kaposi's sarcoma incidence in southern Sardinia (Italy) in 1998–2002 found the highest rate recorded in the island of 2.49 per 100 000 per year (standardised).

Kaposi's sarcoma: An update

While there have been many important advances in the study of Kaposi's sarcoma (KS), it remains both a challenge and an enigma in many ways. Kaposi's original description of "multiple idiopathic hemorrhagic sarcoma[s]" in patients who died within 2-3 years resembles KS in AIDS more than classic KS in elderly men of Italian, Jewish, or Mediterranean lineage, in whom the disease is usually benign. KS had been evident in about one-third of those with early AIDS, often as its presenting sign, a pattern markedly reduced in recent times since the introduction of highly active anti-retroviral therapy (HAART). The most important advance has been the convincing etiologic linkage of KS with human herpesvirus 8 (HHV-8), which is necessary but not sufficient. It has a low prevalence in the general population of the USA and UK, with an intermediate rate in Italy and Greece, and a high one in Uganda. KS risk may be significantly lower in AIDS patients with a history of anti-herpes therapy. Many aspects of HHV-8, including its transmission pattern and different genospecies, are being scrutinized. The diagnosis of KS may be difficult. One should be aware of KS clinical variants, including telangiectatic, eccymotic, and keloidal KS. One must consider a number of other disorders, including bacillary angiomatosis. HHV-8 DNA sequences in dermatofibromas and other tumors should probably not be viewed as representing a marker for KS. Therapeutic options vary for KS. Intralesional and low-dose outpatient intravenous vinblastine may be valuable, as immunosuppression with KS is not a good idea if it can be avoided. Anti-herpes virus therapy may have potential for wide use, especially in preventing the development of KS in at risk populations, such as HHV-8 seropositive individuals undergoing transplantation surgery.

Molecular genetics of Kaposi's sarcoma-associated herpesvirus (human herpesvirus-8) epidemiology and pathogenesis

Kaposi's sarcoma had been recognized as unique human cancer for a century before it manifested as an AIDS-defining illness with a suspected infectious etiology. The discovery of Kaposi's sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus-8, in 1994 by using representational difference analysis, a subtractive method previously employed for cloning differences in human genomic DNA, was a fitting harbinger for the powerful bioinformatic approaches since employed to understand its pathogenesis in KS. Indeed, the discovery of KSHV was rapidly followed by publication of its complete sequence, which revealed that the virus had coopted a wide armamentarium of human genes; in the short time since then, the functions of many of these viral gene variants in cell growth control, signaling apoptosis, angiogenesis, and immunomodulation have been characterized. This critical literature review explores the pathogenic potential of these genes within the framework of current knowledge of the basic herpesvirology of KSHV, including the relationships between viral genotypic variation and the four clinicoepidemiologic forms of Kaposi's sarcoma, current viral detection methods and their utility, primary infection by KSHV, tissue culture and animal models of latent- and lytic-cycle gene expression and pathogenesis, and viral reactivation from latency. Recent advances in models of de novo endothelial infection, microarray analyses of the host response to infection, receptor identification, and cloning of full-length, infectious KSHV genomic DNA promise to reveal key molecular mechanisms of the candidate pathogeneic genes when expressed in the context of viral infection.

Causality or coincidence: may the slow disappearance of helminths be responsible for the imbalances in immune control mechanisms?

Intestinal infection continues to be a problem worldwide and helminths, which currently infect billions of individuals, are primary culprits. The major burden of disease falls on the populations of developing countries, given that over the last four to five decades helminth infections are disappearing in industrialized societies. In developing countries, a major source of immunomodulatory signals in post-natal life are parasites, particularly helminths, which, unlike most bacteria and viruses, selectively stimulate Th2 function. Helminths and their eggs are probably the most potent stimulators of mucosal Th2 responses. Responses elicited by worms can modulate immune reactions to other parasites, bacterial, viral infections and several unrelated diseases. Bacterial and protozoal infections may also protect against atopy and asthma, through the induction of the Th1 regulatory responses. Today, people in developed countries often live in ultra-hygienic environments, avoiding exposure to viruses, bacteria, ectoparasites and endoparasites, particularly helminths. Perhaps failure to acquire worms and experience mucosal Th2 conditioning predisposes to unrelated diseases. In contrast to this hypothesis it has also been suggested that Th2 responses can make the host more susceptible to other important diseases and to contribute to the spread of them.