Mycoplasmas and oncogenesis: persistent infection and multistage malignant transformation

In situ immunohistochemical detection of intracellular Mycoplasma salivarium in the epithelial cells of oral leukoplakia

Background

Mycoplasmas are the smallest free-living organisms; Mycoplasma salivarium and Mycoplasma orale are the most common species isolated from the oropharynx. Oral leukoplakia is the most prevalent potentially malignant disorder of the oral mucosa; its etiology has not been defined. Our previous study with DNA-binding fluorescent dye suggested the presence of mycoplasmas in the epithelial cells of leukoplakia tissue.

Objective

Our aim was to detect M. salivarium in the epithelial cells of leukoplakia by immunohistochemistry.

Design

We produced a polyclonal antibody (PAb) reactive to Mycoplasma by injecting a rabbit with M. salivarium cells (ATCC 23064) mixed with complete Freund's adjuvant and a monoclonal antibody specific to M. salivarium by injecting M. salivarium cells (ATCC 23557) mixed with complete Freund's adjuvant into the footpads of a rat. Then, we attempted to detect M. salivarium in the epithelium of leukoplakia tissues by immunohistochemistry.

Results

We obtained an antimycoplasma rabbit PAb reactive to all seven Mycoplasma species used in this study. Three hybridoma clones producing monoclonal antibodies specific to M. salivarium were obtained, and an M. salivarium-specific monoclonal antibody, designated 7-6H, was established. Immunohistochemistry with these antibodies revealed M. salivarium in the epithelial cells of leukoplakia with hyperplasia and hyperkeratosis on histology. PCR and sequencing verified the presence of M. salivariumDNA in the epithelial cells of leukoplakia.

Conclusion

Intracellular M. salivarium was identified in the epithelial cells of leukoplakia.

Mycoplasmas and cancer: focus on nucleoside metabolism

The standard of care for patients suffering cancer often includes treatment with nucleoside analogues (NAs). NAs are internalized by cell-specific nucleobase/nucleoside transporters and, after enzymatic activation (often one or more phosphorylation steps), interfere with cellular nucleo(s)(t)ide metabolism and DNA/RNA synthesis. Therefore, their efficacy is highly dependent on the expression and activity of nucleo(s)(t)ide-metabolizing enzymes, and alterations thereof (e.g. by down/upregulated expression or mutations) may change the susceptibility to NA-based therapy and/or confer drug resistance. Apart from host cell factors, several other variables including microbial presence may determine the metabolome (i.e. metabolite concentrations) of human tissues. Studying the diversity of microorganisms that are associated with the human body has already provided new insights in several diseases (e.g. diabetes and inflammatory bowel disease) and the metabolic exchange between tissues and their specific microbiota was found to affect the bioavailability and toxicity of certain anticancer drugs, including NAs. Several studies report a preferential colonization of tumor tissues with some mycoplasma species (mostly Mycoplasma hyorhinis). These prokaryotes are also a common source of cell culture contamination and alter the cytostatic activity of some NAs in vitro due to the expression of nucleoside-catabolizing enzymes. Mycoplasma infection may therefore bias experimental work with NAs, and their presence in the tumor microenvironment could be of significance when optimizing nucleoside-based cancer treatment.

Detection of mycoplasma infection in circulating tumor cells in patients with hepatocellular carcinoma

Many studies have shown that persistent infections of bacteria promote carcinogenesis and metastasis. Infectious agents and their products can modulate cancer progression through the induction of host inflammatory and immune responses. The presence of circulating tumor cells (CTCs) is considered as an important indicator in the metastatic cascade. We unintentionally produced a monoclonal antibody (MAb) CA27 against the mycoplasmal p37 protein in mycoplasma-infected cancer cells during the searching process of novel surface markers of CTCs. Mycoplasma-infected cells were enriched by CA27-conjugated magnetic beads in the peripheral blood mononuclear cells in patients with hepatocellular carcinoma (HCC) and analyzed by confocal microscopy with anti-CD45 and CA27 antibodies. CD45-negative and CA27-positive cells were readily detected in three out of seven patients (range 12-30/8.5 ml blood), indicating that they are mycoplasma-infected circulating epithelial cells. CA27-positive cells had larger size than CD45-positive hematological lineage cells, high nuclear to cytoplasmic ratios and irregular nuclear morphology, which identified them as CTCs. The results show for the first time the existence of mycoplasma-infected CTCs in patients with HCC and suggest a possible correlation between mycoplasma infection and the development of cancer metastasis.

Mycoplasma genitalium and cancer: a brief review

Approximately, 15-20% of all cancers worldwide are caused by infectious agents. Understanding the role of infectious agents on cancer development might be useful for developing new approaches to its prevention. Mycoplasma genitalium is a clinically important sexually transmitted pathogen that has been associated with several human diseases. There have been a few studies suggestive of probable roles of Mycoplasma genitalium in cancer development, including prostate and ovarian cancers and lymphomas, but the role of this microorganism like other Mycoplasma species in neoplasia is still conjectural. Considering the prevalence of Mycoplasma genitalium infections and also the emergence of resistant strains, Mycoplasma genitalium needs more attention in the infectious agent cancer-causing research area.

Mycoplasma hyorhinis activates the NLRP3 inflammasome and promotes migration and invasion of gastric cancer cells

BACKGROUND

Mycoplasma hyorhinis (M.hyorhinis, M.hy) is associated with development of gastric and prostate cancers. The NLRP3 inflammasome, a protein complex controlling maturation of important pro-inflammatory cytokines interleukin (IL)-1β and IL-18, is also involved in tumorigenesis and metastasis of various cancers.

METHODOLOGY/PRINCIPAL FINDINGS

To clarify whether M.hy promoted tumor development via inflammasome activation, we analyzed monocytes for IL-1β and IL-18 production upon M.hy challenge. When exposed to M.hy, human monocytes exhibited rapid and robust IL-1β and IL-18 secretion. We further identified that lipid-associated membrane protein (LAMP) from M.hy was responsible for IL-1β induction. Applying competitive inhibitors, gene specific shRNA and gene targeted mice, we verified that M.hy induced IL-1β secretion was NLRP3-dependent in vitro and in vivo. Cathepsin B activity, K(+) efflux, Ca(2+) influx and ROS production were all required for the NLRP3 inflammasome activation by M.hy. Importantly, it is IL-1β but not IL-18 produced from macrophages challenged with M.hy promoted gastric cancer cell migration and invasion.

CONCLUSIONS

Our data suggest that activation of the NLRP3 inflammasome by M.hy may be associated with its promotion of gastric cancer metastasis, and anti-M.hy therapy or limiting NLRP3 signaling could be effective approach for control of gastric cancer progress.

Mycoplasma fermentans inhibits the activity of cellular DNA topoisomerase I by activation of PARP1 and alters the efficacy of its anti-cancer inhibitor

To understand the effects of the interaction between Mycoplasma and cells on the host cellular function, it is important to elucidate the influences of infection of cells with Mycoplasma on nuclear enzymes such as DNA Topoisomerase type I (Topo I). Human Topo I participates in DNA transaction processes and is the target of anti-cancer drugs, the camptothecins (CPTs). Here we investigated the mechanism by which infection of human tumor cells with Mycoplasma fermentans affects the activity and expression of cellular Topo I, and the anti-cancer efficacy of CPT. Human cancer cells were infected or treated with live or sonicated M. fermentans and the activity and expression of Topo I was determined. M. fermentans significantly reduced (by 80%) Topo I activity in the infected/treated tumor cells without affecting the level of Topo I protein. We demonstrate that this reduction in enzyme activity resulted from ADP-ribosylation of the Topo I protein by Poly-ADP-ribose polymerase (PARP-1). In addition, pERK was activated as a result of the induction of the MAPK signal transduction pathway by M. fermentans. Since PARP-1 was shown to be activated by pERK, we concluded that M. fermentans modified the cellular Topo I activity by activation of PARP-I via the induction of the MAPK signal transduction pathway. Moreover, the infection of tumor cells with M. fermentans diminished the inhibitory effect of CPT. The results of this study suggest that modification of Topo I activity by M. fermentans may alter cellular gene expression and the response of tumor cells to Topo I inhibitors, influencing the anti-cancer capacity of Topo I antagonists.

Concomitant infections with human papillomavirus and various mycoplasma and ureaplasma species in women with abnormal cervical cytology

PURPOSE

The objective of the present study is to verify possible association between infections with mycoplasmas and ureaplasmas and the presence of HPV infections in women diagnosed with abnormal cervical cytology.

MATERIAL/METHODS

The investigation included 387 non-pregnant women among whom: 62 were diagnosed with ASCUS, 167 with LSIL, 27 with HSIL, 49 with cervical carcinomas, and 82 females with normal cytology.The presence of HPV infection and identification of both ureaplasma and mycoplasma were confirmed by PCR using specific primers.

RESULTS

HPV infections were demonstrated in 156 females (40%), with mycoplasmas and/or ureaplasmas were confirmed in 93 cases (24%). In HPV-positive patients, infections with mycoplasmas/ureaplasmas were more frequent, particularly for ureaplasmas (U. urealyticum p=0.004, U. parvum p=0.027). The percentage of females infected with U. urealyticum significantly increased in women diagnosed with cervical carcinoma as compared to controls.The statistical analysis demonstrated that the risk of HPV infection while already infected with any of the four analyzed species of Mycoplasmataceae increased two-fold. With concomitant of U. urealyticum infection, the risk of HPV infection was 4.7-fold greater than in the absence U. urealyticum infection.

CONCLUSION

Since the presence of U. urealyticum associates significantly with the HPV infection, genotyping of the ureaplasma species should be recomended.

Exosomes released from Mycoplasma infected tumor cells activate inhibitory B cells

Mycoplasmas cause numerous human diseases and are common opportunistic pathogens in cancer patients and immunocompromised individuals. Mycoplasma infection elicits various host immune responses. Here we demonstrate that mycoplasma-infected tumor cells release exosomes (myco+ exosomes) that specifically activate splenic B cells and induce splenocytes cytokine production. Induction of cytokines, including the proinflammatory IFN-γ and the anti-inflammatory IL-10, was largely dependent on the presence of B cells. B cells were the major IL-10 producers. In splenocytes from B cell deficient μMT mice, induction of IFN-γ+ T cells by myco+ exosomes was greatly increased compared with wild type splenocytes. In addition, anti-CD3-stimulated T cell proliferation was greatly inhibited in the presence of myco+ exosome-treated B cells. Also, anti-CD3-stimulated T cell signaling was impaired by myco+ exosome treatment. Proteomic analysis identified mycoplasma proteins in exosomes that potentially contribute to the effects. Our results demonstrate that mycoplasma-infected tumor cells release exosomes carrying mycoplasma components that preferentially activate B cells, which in turn, are able to inhibit T cell activity. These results suggest that mycoplasmas infecting tumor cells can exploit the exosome pathway to disseminate their own components and modulate the activity of immune cells, in particular, activate B cells with inhibitory activity.

Molecular prevalence of Bartonella, Babesia, and hemotropic Mycoplasma sp. in dogs with splenic disease

BACKGROUND

Among diseases that cause splenomegaly in dogs, lymphoid nodular hyperplasia (LNH), splenic hemangiosarcoma (HSA), and fibrohistiocytic nodules (FHN) are common diagnoses. The spleen plays an important role in the immunologic control or elimination of vector-transmitted, blood-borne pathogens, including Bartonella sp., Babesia sp., and hemotropic Mycoplasma sp.

OBJECTIVE

To compare the prevalence of Bartonella sp., Babesia sp., and hemotropic Mycoplasma sp. DNA in spleens from dogs with LNH, HSA, and FHN.

MATERIALS AND METHODS

Paraffin-embedded, surgically obtained biopsy tissues from LNH (N = 50), HSA (N = 50), and FHN (N = 37) were collected from the anatomic pathology archives. Spleens from specific pathogen-free (SPF) dogs (N = 8) were used as controls. Bartonella sp., Babesia sp., and Mycoplasma sp. DNA was amplified by PCR, followed by DNA sequencing.

RESULTS

Bartonella sp. DNA was more prevalent in FHN (29.7%) and HSA (26%) as compared to LNH (10%) (P = .019, .0373, respectively) or control spleens (0.0%). The prevalence of Babesia sp. and hemotropic Mycoplasma sp. DNA was significantly lower than Bartonella sp. DNA in HSA (P = .0005, .006, respectively) and FHN (P = .003, .0004, respectively). There was no statistically significant difference in DNA prevalence among the 3 genera in the LNH group.

CONCLUSIONS

The higher prevalence of Bartonella sp. in FHN and HSA warrants future investigations to determine if this bacterium plays a role in the development of these splenic diseases.

Association of Mycoplasma hominis infection with prostate cancer

The origin of chronic inflammation preceding the development of prostate cancer (PCa) remains unknown. We investigated possible involvement of mycoplasma infection in PCa by screening prostate biopsies from two groups of Russian men undergoing PCa diagnosis. M. hominis was detected by standard PCR in 15% of the 125 patients in the first group and by quantitative real-time PCR in 37.4% of the 123 men in the second group. In both groups, stratification of patients according to diagnosis showed that M. hominis was present at three times higher frequency in patients with PCa than in those with benign prostatic hyperplasia. No M. hominis was detected in the prostates of 27 men without detectable prostate disease. In addition, PCa-positive men had higher titers of antibodies against M. hominis and average PSA levels were higher in M. hominis-positive men. These data, together with previous observations linking mycoplasma infection with cell transformation, genomic instability and resistance to apoptosis, suggest that M. hominis infection may be involved in PCa development and may, therefore, be a potential PCa marker and/or target for improved prevention and treatment of this disease.

Detection of antibodies directed at M. hyorhinis p37 in the serum of men with newly diagnosed prostate cancer

Background

Recent epidemiologic, genetic, and molecular studies suggest infection and inflammation initiate certain cancers, including cancers of the prostate. Over the past several years, our group has been studying how mycoplasmas could possibly initiate and propagate cancers of the prostate. Specifically, Mycoplasma hyorhinis encoded protein p37 was found to promote invasion of prostate cancer cells and cause changes in growth, morphology and gene expression of these cells to a more aggressive phenotype. Moreover, we found that chronic exposure of benign human prostate cells to M. hyorhinis resulted in significant phenotypic and karyotypic changes that ultimately resulted in the malignant transformation of the benign cells. In this study, we set out to investigate another potential link between mycoplasma and human prostate cancer.

Methods

We report the incidence of men with prostate cancer and benign prostatic hyperplasia (BPH) being seropositive for M. hyorhinis. Antibodies to M. hyorhinis were surveyed by a novel indirect enzyme-linked immunosorbent assay (ELISA) in serum samples collected from men presenting to an outpatient Urology clinic for BPH (N = 105) or prostate cancer (N = 114) from 2006-2009.

Results

A seropositive rate of 36% in men with BPH and 52% in men with prostate cancer was reported, thus leading us to speculate a possible connection between M. hyorhinis exposure with prostate cancer.

Conclusions

These results further support a potential exacerbating role for mycoplasma in the development of prostate cancer.

Medulloblastoma and Brucellosis - Molecular Evidence of Brucella sp in Association with Central Nervous System Cancer

Neurobrucellosis has been reported to cause lesions in a number of different locations in the central nervous system. Histologically or radiologically, these lesions were consistent with an infection. In response to parents who believed their child's brain tumor, histologically typical of medulloblastoma, was in reality neurobrucellosis, formalin-fixed paraffin-embedded tumor tissue from the medulloblastoma was sectioned, DNA extracted, and tested by polymerase chain reaction (PCR). Specific primer/probe sets, designed in our laboratory to target Brucella species, B. melitensis, B. abortus and B. suis, and designated OMP31, B-m, B-a and B-s, respectively, were used in TaqMan real-time PCR to amplify those gene targets in two separate blocks of the child's tumor. Sections from two blocks were positive only for Brucella species. Although the patient grew up in a European country known to harbor brucella in foods, such as unpasturized milk and cheese, the patient was seronegative for B. mellitensis, B. suis, and B. abortus. In an effort to test whether a relationship existed between the presence of brucella and medulloblastoma, 20 medulloblastomas were retrieved from the tissue repository of the AFIP. The above four primer/probe sets were again used to amplify brucella DNA. Five of 20 tumors (25%) contained Brucella species DNA by the OMP31 primer/probe set. None of the 20 medulloblastomas had specific sequences for B. mellitensis, B. suis, or B. abortus. Is chronic brucellosis similar to other infectious agents such as helicobacter that is associated with tumor formation?

The struggle within: microbial influences on colorectal cancer

Recently, an unprecedented effort has been directed at understanding the interplay between chronic inflammation and development of cancer, with the case of inflammatory bowel disease (IBD)-associated colorectal cancer at the forefront of this research endeavor. The last decade has been particularly fertile, with the discovery of numerous innovative paradigms linking various inflammatory, proliferative, and innate and adaptive immune signaling pathways to the development of colorectal cancer. Because of the preponderant role of the intestinal microbiota in the initiation and progression of IBD, recent efforts have been directed at understanding the relationship between bacteria and colorectal cancer. The microbiota and its collective genome, the microbiome, form a diverse and complex ecological community that profoundly impacts intestinal homeostasis and disease states. This review will discuss the differential influence of the microbiota on the development of IBD-associated colorectal cancer and highlight the role of innate immune sensor-dependent as well as -independent mechanisms in this pathology.

Role of bacteria in oncogenesis

Although scientific knowledge in viral oncology has exploded in the 20th century, the role of bacteria as mediators of oncogenesis has been less well elucidated. Understanding bacterial carcinogenesis has become increasingly important as a possible means of cancer prevention. This review summarizes clinical, epidemiological, and experimental evidence as well as possible mechanisms of bacterial induction of or protection from malignancy.

Mycoplasma hyorhinis infection in gastric carcinoma and its effects on the malignant phenotypes of gastric cancer cells

BACKGROUND

Mycoplasma hyorhinis infection has been postulated to play a role in the development of several types of cancer, but the direct evidence and mechanism remained to be determined.

METHODS

Immunohistochemistry assay and nested polymerase-chain reaction (PCR) were performed to examine the mycoplasma hyorhinis infection in gastric cancer tissues. Statistical analysis was used to check the association between mycoplasma infection and clinicopathologic parameters. Transwell chamber assay and metastasis assay were used to evaluate mycoplasma hyorhinis' effects on metastasis in vitro and in vivo. Mycoplasma hyorhinis-induced extracellular signal-regulated kinase (ERK) and epidermal growth factor receptor (EGFR) activation were investigated by Western blot.

RESULTS

Mycoplasma hyorhinis infection in gastric cancer tissues was revealed and statistical analysis indicated a significant association between mycoplasma infections and lymph node metastasis, Lauren's Classification, TNM stage, and age of the patients. Mycoplasma hyorhinis promoted tumor cell migration, invasion and metastasis in vitro and in vivo, which was possibly associated with the enhanced phosphorylation of EGFR and ERK1/2. The antibody against p37 protein of Mycoplasma hyorhinis could inhibit the migration of the infected cells.

CONCLUSIONS

The infection of mycoplasma hyorhinis may contribute to the development of gastric cancer and Mycoplasma hyorhinis-induced malignant phenotypes were possibly mediated by p37.

The dual role of thymidine phosphorylase in cancer development and chemotherapy

Thymidine phosphorylase (TP), also known as "platelet-derived endothelial cell growth factor" (PD-ECGF), is an enzyme, which is upregulated in a wide variety of solid tumors including breast and colorectal cancers. TP promotes tumor growth and metastasis by preventing apoptosis and inducing angiogenesis. Elevated levels of TP are associated with tumor aggressiveness and poor prognosis. Therefore, TP inhibitors are synthesized in an attempt to prevent tumor angiogenesis and metastasis. TP is also indispensable for the activation of the extensively used 5-fluorouracil prodrug capecitabine, which is clinically used for the treatment of colon and breast cancer. Clinical trials that combine capecitabine with TP-inducing therapies (such as taxanes or radiotherapy) suggest that increasing TP expression is an adequate strategy to enhance the antitumoral efficacy of capecitabine. Thus, TP plays a dual role in cancer development and therapy: on the one hand, TP inhibitors can abrogate the tumorigenic and metastatic properties of TP; on the other, TP activity is necessary for the activation of several chemotherapeutic drugs. This duality illustrates the complexity of the role of TP in tumor progression and in the clinical response to fluoropyrimidine-based chemotherapy.

Persistent exposure to Mycoplasma induces malignant transformation of human prostate cells

Recent epidemiologic, genetic, and molecular studies suggest infection and inflammation initiate certain cancers, including those of the prostate. The American Cancer Society, estimates that approximately 20% of all worldwide cancers are caused by infection. Mycoplasma, a genus of bacteria that lack a cell wall, are among the few prokaryotes that can grow in close relationship with mammalian cells, often without any apparent pathology, for extended periods of time. In this study, the capacity of Mycoplasma genitalium, a prevalent sexually transmitted infection, and Mycoplasma hyorhinis, a mycoplasma found at unusually high frequency among patients with AIDS, to induce a malignant phenotype in benign human prostate cells (BPH-1) was evaluated using a series of in vitro and in vivo assays. After 19 weeks of culture, infected BPH-1 cells achieved anchorage-independent growth and increased migration and invasion. Malignant transformation of infected BPH-1 cells was confirmed by the formation of xenograft tumors in athymic mice. Associated with these changes was an increase in karyotypic entropy, evident by the accumulation of chromosomal aberrations and polysomy. This is the first report describing the capacity of M. genitalium or M. hyorhinis infection to lead to the malignant transformation of benign human epithelial cells and may serve as a model to further study the relationship between prostatitis and prostatic carcinogenesis.

Improvement of purine and pyrimidine antimetabolite-based anticancer treatment by selective suppression of mycoplasma-encoded catabolic enzymes

Most mycoplasmas are present as commensals, colonising the mucosa of our respiratory and gastrointestinal tract. Experimental data suggest that the long-term association of certain mycoplasma species with mammalian cells might favour host-cell transformation and malignancy. Moreover, increased mycoplasma infection has been noted in several cancers. Despite efforts to develop target-specific anticancer drugs, current cancer treatment still relies on the use of nucleobase or nucleoside-based analogues. Here, we provide experimental evidence that nucleoside-metabolising catabolic enzymes expressed by mycoplasmas substantially compromise the efficacy of nucleoside antimetabolites used in the treatment of cancer. We also suggest potential methods for improving future chemotherapy by suppressing mycoplasma-mediated catabolism of the anticancer nucleoside analogues.

Structural insights into the extracytoplasmic thiamine-binding lipoprotein p37 of Mycoplasma hyorhinis

The Mycoplasma hyorhinis protein p37 has been implicated in tumorigenic transformation for more than 20 years. Though there are many speculations as to its function, based solely on sequence homology, the issue has remained unresolved. Presented here is the 1.6-A-resolution refined crystal structure of M. hyorhinis p37, renamed the extracytoplasmic thiamine-binding lipoprotein (Cypl). The structure shows thiamine pyrophosphate (TPP) and two calcium ions are bound to Cypl and give the first insights into possible functions of the Cypl-like family of proteins. Sequence alignments of Cypl-like proteins between several different species of mycoplasma show that the thiamine-binding site is likely conserved and structural alignments reveal the similarity of Cypl to various binding proteins. While the experimentally determined function of Cypl remains unknown, the structure shows that the protein is a TPP-binding protein, opening up many avenues for future mechanistic studies and making Cypl a possible target for combating mycoplasma infections and tumorigenic transformation.

Human Papillomaviruses and genital co-infections in gynaecological outpatients

Background

High grade HPV infections and persistence are the strongest risk factors for cervical cancer. Nevertheless other genital microorganisms may be involved in the progression of HPV associated lesions.

Methods

Cervical samples were collected to search for human Papillomavirus (HPV), bacteria and yeast infections in gynaecologic outpatients. HPV typing was carried out by PCR and sequencing on cervical brush specimens. Chlamydia trachomatis was identified by strand displacement amplification (SDA) and the other microorganisms were detected by conventional methods.

Results

In this cross-sectional study on 857 enrolled outpatients, statistical analyses revealed a significant association of HPV with C. trachomatis and Ureaplasma urealyticum (at high density) detection, whereas no correlation was found between HPV infection and bacterial vaginosis, Streptococcus agalactiae, yeasts, Trichomonas vaginalis and U. urealyticum. Mycoplasma hominis was isolated only in a few cases both in HPV positive and negative women and no patient was infected with Neisseria gonorrhoeae.

Conclusion

Although bacterial vaginosis was not significantly associated with HPV, it was more common among the HPV positive women. A significant association between HPV and C. trachomatis was found and interestingly also with U. urealyticum but only at a high colonization rate. These data suggest that it may be important to screen for the simultaneous presence of different microorganisms which may have synergistic pathological effects.

Mycoplasma contamination of murine embryonic stem cells affects cell parameters, germline transmission and chimeric progeny

Murine embryonic stem cells (mESCs) inoculated at passage P13 with the mycoplasma species M. hominis, M. fermentans and M. orale and cultured over 20 passages showed reduced growth rate and viability (P < 0.0001) compared to control mESCs. Spectral karyotypic analysis of mycoplasma-infected mESCs showed a number of non-clonal chromosomal aberrations which increased with the duration of infection. The differentiation status of the infected mESCs was most affected at passage P13+6 where the infection was strongest and 46.3% of the mESCs expressed both POU5F1 and SSEA-1 markers whereas 84.8% of control mESCs expressed both markers. The percentage of germline chimeras from mycoplasma-infected mESCs was examined after blastocyst injection and embryo transfer to suitable recipients at different passages and, compared to the respective control group, was most affected at passage P13+5 (50% vs. 90%; P < 0.07). Further reductions were obtained at the same passage in the percentage of litters born (50% vs. 100%; P < 0.07) and in the percentage of pups born (22% vs. 45%; P < 0.001). Thirty three chimeras (39.8%) obtained from blastocyst injection with mycoplasma-infected mESCs showed reduced body weight (P < 0.0001), nasal discharge, osteoarthropathia, and cachexia. Flow cytometric analysis of plasma from chimeras produced with mycoplasma-infected mESCs revealed statistically significant differences in the proportions of T-cells and increased levels of IgG1 (P < 0.001), IgG2a (P < 0.05) and IgM (P < 0.05), anti-DNA antibodies (P < 0.05) and rheumatoid factor (P < 0.01). The present data indicate that mycoplasma contamination of mESCs affects various cell parameters, germline transmission, and postnatal development of the resulting chimeras.

The cytostatic activity of pyrimidine nucleosides is strongly modulated by Mycoplasma hyorhinis infection: Implications for cancer therapy

Nucleoside analogues are widely used as chemotherapeutic agents in the treatment of cancer. Several cancers are reported to be associated with mycoplasmas (i.e. Mycoplasma hyorhinis), which contain a number of nucleoside-metabolizing enzymes. Pyrimidine nucleoside analogues, such as 5-fluoro-2'-deoxyuridine (FdUrd), 5-trifluorothymidine (TFT) and 5-halogenated 2'-deoxyuridines can be degraded by thymidine phosphorylase (TP) to their inactive bases. We found in M. hyorhinis-infected MCF-7 breast carcinoma cells (MCF-7/HYOR) a mycoplasma-encoded TP that dramatically (20-150-fold) reduces the cytostatic activity of these compounds. The reduction in cytostatic activity could be fully restored in the presence of TPI (5-chloro-6-[1-(2-iminopyrrolidinyl)methyl]uracil hydrochloride), a known inhibitor of human TP. This observation is in agreement with the markedly decreased formation of active metabolite (i.e. FdUMP for FdUrd) or diminished drug incorporation into nucleic acids (i.e. for TFT and 5-bromo-2'-deoxyuridine) in MCF-7/HYOR cells compared with uninfected MCF-7 cells. Antimetabolite formation is fully restored in the presence of TPI. In contrast, 5-fluoro-5'-deoxyuridine (5'DFUR), an intermediate metabolite of capecitabine, was markedly more cytostatic in MCF-7/HYOR cells than in uninfected cells, due to the activation of this prodrug by the mycoplasma-encoded TP. Thus, our data reveal that M. hyorhinis expresses a TP that activates 5'DFUR but inactivates FdUrd, TFT and 5-halogenated 2'-deoxyuridines, and that is highly sensitive to the inhibitory effect of the TP inhibitor TPI. Given the association of M. hyorhinis with several human cancers, our findings suggest that pyrimidine nucleoside-based but not 5FU-based anti-cancer therapy might be more effective when combined with a mycoplasmal TP inhibitor.

Mycoplasma infection transforms normal lung cells and induces bone morphogenetic protein 2 expression by post-transcriptional mechanisms

Bone morphogenetic protein 2 (BMP2) is an essential growth factor and morphogen, whose pattern and level of expression profoundly influences development and physiology. We present the novel finding that mycoplasma infection induces BMP2 RNA production in six cell lines of diverse types (mesenchymal, epithelial, and myeloid). Mycoplasma infection triggered the expression of mature secreted BMP2 protein in BEAS-2B cells (immortalized human bronchial epithelial cells), which normally do not express BMP2, and further increased BMP2 production in A549 cells (lung adenocarcinoma cells). Indeed, mycoplasma is as strong an experimental inducer as inflammatory cytokines and retinoic acid. Second, we showed that post-transcriptional mechanisms including regulation of RNA stability, rather than transcriptional mechanisms, contributed to the increased BMP2 expression in mycoplasma-infected cells. Furthermore, a novel G-rich oligonucleotide, AS1411 that binds the post-transcriptional regulator nucleolin induced BMP2 exclusively in infected cells. Finally, BMP2 stimulated proliferation in BEAS-2B cells transformed by chronic mycoplasma infection, as demonstrated by treatment with Noggin, a BMP2 antagonist. These findings have important implications regarding the effects of mycoplasma on BMP2-regulated processes, including cell proliferation, differentiation, and apoptosis.

Amyloid-beta peptide degradation in cell cultures by mycoplasma contaminants

Background

Cell cultures have become an indispensable tool in Alzheimer's disease research for studying amyloid-β (Aβ) metabolism. It is estimated that up to 35% of cell cultures in current use are infected with various mycoplasma species. In contrast with common bacterial and fungal infections, contaminations of cell cultures with mycoplasmas represent a challenging issue in terms of detectability and prevention. Mycoplasmas are the smallest and simplest self-replicating bacteria and the consequences of an infection for the host cells are variable, ranging from no apparent effect to induction of apoptosis.

Findings

Here we present evidence that mycoplasmas from a cell culture contamination are able to efficiently and rapidly degrade extracellular Aβ. As a result, we observed no accumulation of Aβ in the conditioned medium of mycoplasma-positive cells stably transfected with the amyloid-β precursor protein (APP). Importantly, eradication of the mycoplasma contaminant – identified as M. hyorhinis – by treatments with a quinolone-based antibiotic, restored extracellular Aβ accumulation in the APP-transfected cells.

Conclusion

These data show that mycoplasmas degrade Aβ and thus may represent a significant source of variability when comparing extracellular Aβ levels in different cell lines. On the basis of these results, we recommend assessment of mycoplasma contaminations prior to extracellular Aβ level measurements in cultured cells.

p37 from Mycoplasma hyorhinis promotes cancer cell invasiveness and metastasis through activation of MMP-2 and followed by phosphorylation of EGFR

High Mycoplasma infection in gastric cancer tissues suggests a possible association between Mycoplasma infection and tumorigenesis. By using human gastric cancer cells AGS and mouse melanoma cells B16F10 stably expressing p37, the major immunogen of Mycoplasma hyorhinis, we found that p37 enhanced cell motility, migration, and invasion in vitro. With experimental metastasis model in C57BL/6 mice, p37 adenovirus-infected B16F10 cells formed more metastasis lesions in the lung. Furthermore, p37 promoted the phosphorylation of epidermal growth factor receptor (EGFR) and extracellular signal-regulated kinase and the activity of matrix metalloproteinase-2 (MMP-2). Inhibitor of MMPs significantly blocked p37-induced EGFR but has little effect on extracellular signal-regulated kinase phosphorylation, whereas the p37-induced MMP-2 activation was only partially suppressed by inhibitor of MEK1/2 or by inhibitor of EGFR. However, all these inhibitors significantly reduced the p37-induced invasiveness of AGS cells. These results suggest that p37 may stimulate invasion by increasing the activity of MMP-2, thereby inducing EGFR phosphorylation and contributing to tumor metastasis on M. hyorhinis infection. p37 and its regulated molecules could be the potential targets for cancer therapy.

Mycoplasma infection suppresses p53, activates NF-kappaB and cooperates with oncogenic Ras in rodent fibroblast transformation

Prokaryotes of the genus Mycoplasma are the smallest cellular organisms that persist as obligate extracellular parasites. Although mycoplasma infection is known to be associated with chromosomal instability and can promote malignant transformation, the mechanisms underlying these phenomena remain unknown. Since persistence of many cellular parasites requires suppression of apoptosis in host cells, we tested the effect of mycoplasma infection on the activity of the p53 and nuclear factor (NF)-kappaB pathways, major mechanisms controlling programmed cell death. To monitor the activity of p53 and NF-kappaB in mycoplasma-infected cells, we used a panel of reporter cell lines expressing the bacterial beta-galactosidase gene under the control of p53- or NF-kappaB-responsive promoters. Cells incubated with media conditioned with different species of mycoplasma showed constitutive activation of NF-kappaB and reduced activation of p53, common characteristics of the majority of human tumor cells, with M. arginini having the strongest effect among the species tested. Moreover, mycoplasma infection reduced the expression level and inducibility of an endogenous p53-responsive gene, p21(waf1), and inhibited apoptosis induced by genotoxic stress. Infection with M. arginini made rat and mouse embryo fibroblasts susceptible to transformation with oncogenic H-Ras, whereas mycoplasma-free cells underwent irreversible p53-dependent growth arrest. Mycoplasma infection was as effective as shRNA-mediated knockdown of p53 expression in making rodent fibroblasts permissive to Ras-induced transformation. These observations indicate that mycoplasma infection plays the role of a p53-suppressing oncogene that cooperates with Ras in cell transformation and suggest that the carcinogenic and mutagenic effects of mycoplasma might be due to inhibition of p53 tumor suppressor function by this common human parasite.

A novel cerebral microangiopathy with endothelial cell atypia and multifocal white matter lesions: a direct mycoplasmal infection?

We present 3 sporadic cases of a subacute to chronic, progressive motor (i.e. weakness, ataxia, spasticity, dysarthria, and dysphagia) and cognitive disorder in adults of both sexes, without proven immunocompromise or malignancy. Neuroimaging studies revealed tiny calcifications with atrophy of the cerebrum, pons, and midbrain in 1 patient, cerebral atrophy in another, and cerebral atrophy and periventricular white matter hyperintensities in the third. Clinical diagnoses included cortico-pontine-cerebellar degeneration, mixed neurodegenerative disorder, progressive supranuclear palsy, diffuse Lewy body disease, and Lyme disease. One atrophic brain revealed widely disseminated, millimeter-sized gray lesions in cerebral white matter and obscured anatomic markings of the basis pontis. The most conspicuous microscopic feature in all was capillaries with focally piled up endothelial nuclei, some of which appeared to be multinucleated, or enlarged, hyperchromatic crescentic single nuclei. Although seen mostly without associated damage, they were also noted with white matter lesions displaying vacuolation, demyelination, spheroids, necrosis, vascular fibrosis, and mineralization; these were most severe in the basis pontis. Immunostains and probes to herpes simplex virus-I, -II, and -8; adenovirus, cytomegalovirus, varicella-zoster, Epstein-Barr virus, measles, JC virus, and herpes hominis virus-6 were negative. Electron microscopy revealed no virions in endothelial cells with multilobed or multiple nuclei and duplicated basal laminae. However, mycoplasma-like bodies, mostly 400 to 600 nm in size, were found in endothelial cell cytoplasm and capillary lumina. Platelets adhered to affected endothelial cells. Polymerase chain reaction and immunohistochemistry of fixed samples for Mycoplasma fermentans were negative; other species of Mycoplasma remain viable pathogenic candidates.

Exogenous mycoplasmal p37 protein alters gene expression, growth and morphology of prostate cancer cells

We previously showed that the Mycoplasma hyorhinis-encoded protein p37 can promote invasion of cancer cells in a dose-dependent manner, an effect that was blocked by monoclonal antibodies specific for p37. In this study, we further elucidated changes in growth, morphology and gene expression in prostate cancer cell lines when treated with exogenous p37 protein. Incubation with recombinant p37 caused significant nuclear enlargement, denoting active, anaplastic cells and increased the migratory potential of both PC-3 and DU145 cells. Microarray analysis of p37-treated and untreated cells identified eight gene expression clusters that could be broadly classified into three basic patterns. These were an increase in both cell lines, a decrease in either cell line or a cell line-specific differential trend. The most represented functional gene categories included cell cycle, signal transduction and metabolic factors. Taken together, these observations suggest that p37 potentiates the aggressiveness of prostate cancer and thus molecular events triggered by p37 maybe target for therapy.

Matrix metalloproteinase induction in the tumor stroma does not depend on CD147 expression in murine B16 melanoma

BACKGROUND

It was conclusively demonstrated that the cell surface glycoprotein CD147 on tumor cells mediates induction of matrix metalloproteinases (MMPs) by stromal cells in humans. However, for murine models such evidence remains elusive.

METHODS AND RESULTS

To address the impact of CD147 on MMP expression in the murine B16 melanoma model, we consequently stably knocked down CD147 expression in two B16 sublines. The CD147 knockdown remained stable under in vivo conditions as confirmed by immunohistochemistry. However, no differences in MMP-2, MMP-9 and MT1-MMP expression by stromal and tumor cells were detectable in CD147+ and CD147- tumors. Since the tumor microenvironment is a complex system, involving several cell types, the extracellular matrix and plethora soluble factors, we subsequently studied the role of murine CD147 in vitro. Coculture of melanoma cells with different fibroblast cell lines demonstrated that neither CD147+ nor CD147- B16 tumor cells altered the expression of MMP-2 or MMP-9 by the fibroblasts, although we could confirm the susceptibility of these fibroblasts for MMP induction.

CONCLUSIONS

At least for the murine B16 melanoma model, CD147 expression on tumor cells seems not to be crucial for MMP-2, MMP-9 and MT1-MMP induction on tumor-associated stromal cells.

Mycoplasmal membrane protein p37 promotes malignant changes in mammalian cells

Evidence of Mycoplasma hyorhinis infection in human gastric cancer tissues has been found in previous work. In this study, we demonstrate that the expression of p37, a membrane lipoprotein of M. hyorhinis, in mammalian cells induces antisenescence, enhances clonogenicity in soft agar, and co-operates with human epidermal growth factor receptor-related 2 to inhibit cell adhesion. Conversely, truncated p37 protein, with the first 28 amino acids deleted from its N terminal, promotes cell senescence. Taken together, our findings suggest that p37 promotes malignant changes in mammalian cells. With the identification of this molecular component, which is responsible for mycoplasma malignancy-promoting activity, it is possible that a better understanding of the relationship between M. hyorhinis infection and human gastric cancers will lead to novel diagnostics and therapeutics.

Cancer determining information transmission and circulation

Cancer determining information transmission, typically oncogene transfer, is known in many cases of virus initiated tumors. Transmission of carcinogenic information, that stored in plasmids named T-DNAs, is also known to take place in one type of bacteria induced tumor, that caused by Agrobacterium tumefaciens in dicotyledon plants roots. Other mechanisms of carcinogenic information transmission have been more recently recognized, that involve horizontal transfer of genetic material among cells. Despite this latter issue is not new, insights in its mechanisms have just beginning to appear in the literature. Horizontal transfer processes, in addition to the well known vertical transfer from parental to daughter cancer cells, have been tentatively put together with a reductionistic approach in this work, leading to a unifying framework that summarizes the state of the art in carcinogenic information transmission and circulation in the world of cells. Counteracting vectors of carcinogenic information transmission and circulation, such as oncoviruses, has already been shown to be important both in the fields of cancer prevention and therapy. Investigating today unexplored ways of transmission could lead to implement new anticancer strategies.

Effect of mycoplasmas on apoptosis of 32D cells is species-dependent

We previously showed that mycoplasmal infection effectively prevented apoptosis of infected cells, whereas other researchers have indicated that mycoplasmal infection promoted apoptosis. To understand the mechanism underlying this discrepancy, five different species of mycoplasmas were investigated for their effects on apoptosis of interleukin (IL)-3-dependent 32D cells. Results revealed that Mycoplasma fermentans and M. penetrans effectively supported continuous growth of 32D cells after IL-3 withdrawal. M. fermentans was more potent than M. penetrans. This effect was achieved by way of preventing apoptosis and stimulating cell proliferation. On the contrary, M. hominis and M. salivarium accelerated apoptosis of 32D cells. M. genitalium had no significant effect on apoptosis. The RNase protection assay indicated that the proapoptotic and antiapoptotic mycoplasmas altered the expression of major apoptosis regulatory genes differently. The difference in apoptosis regulatory gene expression induced by different species of mycoplasmas might be accountable for their effects on host cell apoptosis.

Induction of Constitutive High-Level Expression of c-Myc in 32D Cells by Mycoplasmas is Associated with their Ability to Prevent Apoptosis and Induce Malignant Transformation

Our previous studies showed that mycoplasmas prevented apoptosis and induced the malignant transformation of mammalian cells. Other studies indicate that c-Myc plays an important role in promoting apoptosis and malignant transformation of cells. To understand the role of c-Myc in the mycoplasma induced apoptosis prevention and malignant cell transformation, 32D cells, an IL-3 dependent cell line, were infected and transformed by different species of mycoplasmas. The expression of Myc and ras gene families, apoptosis and the cell cycle during the infection and transformation were examined. Results showed that c-Myc expression was significantly increased in mycoplasma transformed 32D cells. Withdrawal of IL-3 substantially decreased c-Myc expression and led to cell cycle arrest at the G1 phase followed by rapid apoptosis. Infection by M. fermentans or M. penetrans not only alleviated the sharp decrease of c-Myc expression, rescued 32D cells from cell-cycle arrest and prevented apoptosis in IL-3-free culture, but also induced autonomous growth of 32D cells. Although M. hominis and M. salivarium had the ability neither to prevent apoptosis nor to induce malignant transformation, they were still able to rescue the cells from cell cycle arrest. The expression of ras family did not change significantly during the infection and transformation. These results suggest that constitutive expression of c-Myc appears to be associated with the continuous growth and malignant transformation of 32D cells induced by M. fermentans and M. penetrans, but not with rescuing the cell cycle arrest by the mycoplasmas.

Mycoplasma fermentans and TNF-beta interact to amplify immune-modulating cytokines in human lung fibroblasts

Mycoplasma can establish latent infections and are associated with arthritis, leukemia, and chronic lung disease. We developed an experimental model in which lung cells are deliberately infected with Mycoplasma fermentans. Human lung fibroblasts (HLF) were exposed to live M. fermentans and immune-modulating cytokine release was assessed with and without known inducers of cytokine production. M. fermentans increased IL-6, IL-8/CXCL8, MCP-1/CCL2, and Gro-alpha/CXCL1 production. M. fermentans interacted with TNF-beta to release more IL-6, CXCL8, and CXCL1 than predicted by the responses to either stimulus alone. The effects of live infection were recapitulated by exposure to M. fermentans-derived macrophage-activating lipopeptide-2 (MALP-2), a Toll-like receptor-2- and receptor-6-specific ligand. The synergistic effect of combined stimuli was more pronounced with prolonged incubations. Preexposure to TNF-beta sensitized the cells to subsequent MALP-2 challenge, but preexposure to MALP-2 did not alter the IL-6 response to TNF-beta. Exposure to M. fermentans or MALP-2 did not enhance nuclear localization, DNA binding, or transcriptional activity of NF-kappaB and did not modulate early NF-kappaB activation in response to TNF-beta. Application of specific inhibitors of various MAPKs suggested that p38 and JNK/stress-activated protein kinase were involved in early IL-6 release after exposure to TNF-beta and M. fermentans, respectively. The combined response to M. fermentans and TNF-beta, however, was uniquely sensitive to delayed application of SP-600125, suggesting that JNK/stress-activated protein kinase contributes to the amplification of IL-6 release. Thus M. fermentans interacts with stimuli such as TNF-beta to amplify lung cell production of immune-modulating cytokines. The mechanisms accounting for this interaction can now be dissected with the use of this in vitro model.

Alteration of gene expression profiles during mycoplasma-induced malignant cell transformation

BACKGROUND

Mycoplasmas are the smallest microorganisms capable of self-replication. Our previous studies show that some mycoplasmas are able to induce malignant transformation of host mammalian cells. This malignant transformation is a multistage process with the early infection, reversible and irreversible stages, and similar to human tumor development in nature. The purpose of this study is to explore mechanisms for this malignant transformation.

METHODS

To better understand mechanisms for this unique process, we examined gene expression profiles of C3H cells at different stages of the mycoplasma-induced transformation using cDNA microarray technology. A total of 1185 genes involved in oncogenesis, apoptosis, cell growth, cell-cycle regulation, DNA repair, etc. were examined. Differences in the expression of these genes were compared and analyzed using the computer software AtlasImage.

RESULTS

Among 1185 genes screened, 135 had aberrant expression at the early infection stage, 252 at the reversible stage and 184 at the irreversible stage. At the early infection stage, genes with increased expression (92 genes) were twice more than those with decreased expression (42 genes). The global gene expression at the reversible stage appeared to be more volatile than that at any other stages but still resembled the profile at the early infection stage. The expression profile at the irreversible stage shows a unique pattern of a wide range of expression levels and an increased number of expressing genes, especially the cancer-related genes. Oncogenes and tumor suppressors are a group of molecules that showed significant changes in expression during the transformation. The majority of these changes occurred in the reversible and irreversible stages. A prolonged infection by mycoplasmas lead to the expression of more cancer related genes at the irreversible stage.

CONCLUSION

The results indicate that the expression profiles correspond with the phenotypic features of the cells in the mycoplasma induced transformation process. The early mycoplasma infection stage shares a common phenomenon with many other acute infections, genes with increased expression significantly outnumbering those with decreased expression. The reversible stage is a transition stage between benignancy and malignancy at the molecular level. Aberrant expression of oncogenes and tumor repressors plays a key role in mycoplasma-induced malignant transformation.

Mycoplasma hominis attaches to and locates intracellularly in human spermatozoa

BACKGROUND

The study of sperm-mycoplasma interaction has been focused on the effects of infection on sperm quality, but few studies have reported the direct interaction of this bacterium with spermatozoa.

METHODS

Selected populations of viable, motile and infection-free human spermatozoa from three healthy men were incubated with 15-480 multiplicity of infection (MOI) units of DiIC18-labelled Mycoplasma hominis. Cells were analyzed by means of confocal microscopy and by the eosin-Y dye exclusion test between 10 min and 24 h post-infection.

RESULTS

As early as 10 min post-infection, clusters of M. hominis were seen attached to the sperm head, midpiece or tail. Mycoplasma showed an approximately 2.5-4.5-fold higher interaction with sperm head or tail than with midpiece. Sequential sectioning of infected spermatozoa revealed the intracellular location of M. hominis within cytosolic spaces of head and midpiece regions. A minor proportion of infected spermatozoa showed bent or coiled tails, and/or midpiece thickening. Sperm viability was not altered by M. hominis infection.

CONCLUSIONS

These results provide specific and conclusive evidence of M. hominis attachment and invasiveness towards human sperm cells, which seems not to affect their viability, suggesting that a short-term M. hominis interaction with spermatozoa results in non-apparent or subtle damage, but might have implications for long-term male or couple's fertility.

The cancer stem cell: evidence for its origin as an injured autoreactive T cell

This review explores similarities between lymphocytes and cancer cells, and proposes a new model for the genesis of human cancer. We suggest that the development of cancer requires infection(s) during which antigenic determinants from pathogens mimicking self-antigens are co-presented to the immune system, leading to breaking T cell tolerance. Some level of autoimmunity is normal and necessary for effective pathogen eradication. However, autoreactive T cells must be eliminated by apoptosis when the immune response is terminated. Apoptosis can be deficient in the event of a weakened immune system, the causes of which are multifactorial. Some autoreactive T cells suffer genomic damage in this process, but manage to survive. The resulting cancer stem cell still retains some functions of an inflammatory T cell, so it seeks out sites of inflammation inside the body. Due to its defective constitutive production of inflammatory cytokines and other growth factors, a stroma is built at the site of inflammation similar to the temporary stroma built during wound healing. The cancer cells grow inside this stroma, forming a tumor that provides their vascular supply and protects them from cellular immune response.

As cancer stem cells have plasticity comparable to normal stem cells, interactions with surrounding normal tissues cause them to give rise to all the various types of cancers, resembling differentiated tissue types. Metastases form at an advanced stage of the disease, with the proliferation of sites of inflammation inside the body following a similar mechanism. Immunosuppressive cancer therapies inadvertently re-invigorate pathogenic microorganisms and parasitic infections common to cancer, leading to a vicious circle of infection, autoimmunity and malignancy that ultimately dooms cancer patients. Based on this new understanding, we recommend a systemic approach to the development of cancer therapies that supports rather than antagonizes the immune system.

Lipoprotein p37 from Mycoplasma hyorhinis inhibiting mammalian cell adhesion

p37 protein is a membrane lipoprotein of Mycoplasma hyorhinis, and our previous work showed that there was high ratio of M. hyorhinis infection in human gastric carcinoma. To investigate the possible functions of p37 in cancer development, the nucleotide sequence of p37 gene was modified and expressed well in transfected cells. We found that p37 localized at the Golgi apparatus and could be secreted out of the cell. Human gastric cancer cells AGS, after being transfected with the p37 gene, were smaller, more spherical and easy to detach from each other. Their adhesion to matrix was also diminished and cytoskeleton in these stable p37 AGS cell was rearranged and transcription co-factor beta-actin was transferred to nucleolus with down-regulation of ICAM-1 and integrin beta1. These findings will be helpful for us to elucidate the effects of p37 on eukaryotic cells as well as to better understand the potential relationship between cancer and mycoplasma infection.

Can mycoplasma-mediated oncogenesis be responsible for formation of conventional renal cell carcinoma?

OBJECTIVES

To investigate the association between Mycoplasma sp. infection and conventional renal cell carcinoma (RCC).

METHODS

Normal kidney, renal intratubular neoplasia, and tumor tissue samples from 33 patients with RCC and 35 healthy controls were studied. Molecular DNA analysis was done after nested polymerase chain reaction performed in two steps with seven primers (four outer and three inner) that can recognize at least 15 different Mycoplasma sp.

RESULTS

Mycoplasma sp. DNA was detected in normal kidney, renal intratubular neoplasia, and tumor tissue samples at a ratio of 36%, 67%, and 82%, respectively. In 6 of the 33 patients with RCC, no Mycoplasma sp. was detected from any of the three tissue samples. Mycoplasma sp. DNA was detected in only 5 (14%) of the 35 samples from the control group.

CONCLUSIONS

The relationship between mycoplasma infection and conventional RCC has been investigated for the first time, and a significantly high existence of Mycoplasma sp. DNA was found in the tissues of patients with conventional RCC compared with that found in a healthy control group. This suggests that mycoplasma-mediated multistage carcinogenesis may play a role in the development of RCC.

Deconstructing PTI-1: PTI-1 is a truncated, but not mutated, form of translation elongatin factor 1A1, eEF1A1

The prostate tumor-inducing gene 1 (PTI-1) transcript is detected in various human carcinoma cells. PTI-1 is reported to consist of a 5' untranslated region (5' UTR) homologous to mycoplasma 23S rRNA and a coding region corresponding to a truncated and mutated form of the translation elongation factor 1A, eEF1A. We have found that the PTI-1 transcript may encode a truncated, but not mutated, form of the human isoform eEF1A1. Additionally, the 5' UTR sequence of PTI-1 from genomic DNA of different cell lines and blood samples varies from the original sequence. This 5' -UTR region of PTI-1 presents a fusion of E. coli and Mycoplasma hyorhinis 23S rRNA. We have overexpressed the potential PTI-1 protein in E. coli and various human cell lines. The resulting protein could be detected by western blotting using anti-eEF1A antibodies. However, we were unable to detect the PTI-1 protein in LNCaP cell extracts. The potential roles of the PTI-1 protein in carcinogenesis and the origin of the PTI-1 gene in the human genome are discussed.

Mycoplasma fermentans infection promotes immortalization of human peripheral blood mononuclear cells in culture

Chronic infection or colonization by mycoplasma(s) could gradually and significantly alter many biologic properties of mammalian host cells in culture, including induction of malignant transformation. We examined effects of Mycoplasma fermentans infection on the continuing survival and immortality of human peripheral blood mononuclear cells (PBMCs) from healthy blood donors. Without specific supplemental growth factors, human PBMCs normally die rapidly, with few cells other than macrophages/monocytes surviving after 2 weeks in cultures. Only occasional Epstein-Barr virus (EBV)–positive B lymphocytes would continue to proliferate and undergo spontaneous immortalization. Our present study revealed that infection of human PBMCs in culture with the incognitus and PG18 strains of M fermentans, but surprisingly not with some other strains tested in parallel, markedly enhanced the rate of EBV-positive B lymphocytes to undergo immortalization (74% vs 17%). Compared with spontaneously immortalized PBMCs, the PBMCs immortalized in cultures infected with the mycoplasmas often had prominent karyotype changes with chromosomal loss, gain, or translocations. Furthermore, many of these immortalized B lymphocytes were found to be monoclonal in nature. The in vitro findings would be of relevance to lymphoproliferative disorders that occurred in patients with immune suppression. The mycoplasma-mediated promotional effect in cell immortalization and its potential clinical implications warrant further study.