A novel quasi-viral agent, MaTu, is a two-component system

The detection of renal carcinoma cells in the peripheral blood with an enhanced reverse transcriptase-polymerase chain reaction assay for MN/CA9

BACKGROUND

Using a reverse transcriptase-polymerase chain reaction (RT-PCR) assay, the authors previously determined the expression of MN/CA9 mRNA in renal cell carcinoma (RCC) and its absence in benign renal tissue. In the current study, the utility of an enhanced RT-PCR assay in the detection of renal carcinoma cells in the peripheral blood was assessed.

METHODS

An enhanced MN/CA9 RT-PCR assay was applied to peripheral blood samples from a total of 96 patients. Forty-two patients had renal tumors, including 5 with benign renal lesions, 28 with localized RCC, and 9 with metastatic RCC. Fifty-four control patients without renal tumors were similarly tested. Pathologic staging for patients with localized cancer was T1N0M0 for 5, T2N0M0 for 9, and T3N0M0 for 14 patients.

RESULTS

Cells expressing MN/CA9 were detected in 1 of 54 controls (1.8%) and in 18 of 37 cancer patients (49%). Thirteen of twenty eight patients (46%) with localized RCC and 5 of 9 (56%) with metastatic disease tested positive with the assay. No patient with a benign renal tumor exhibited MN/CA9 expression. All blood test results for patients with clear cell RCC were noted to be positive. No correlation was noted between MN/CA9 results and age, gender, or tumor grade. The differences in MN/CA9 results according to T classification were not statistically significant.

CONCLUSIONS

The enhanced RT-PCR assay for MN/CA9 is a highly specific technique for detecting circulating renal carcinoma cells in the peripheral blood, and it may prove useful in the diagnosis and monitoring of RCC.

Identification of MaTu-MX agent as a new strain of lymphocytic choriomeningitis virus (LCMV) and serological indication of horizontal spread of LCMV in human population

In this study we elucidated the molecular character of MaTu-MX, previously described as an unusual transmissible agent. Amino acid sequencing of peptides generated from a 58-kDa MX-related protein purified from MaTu human carcinoma cells allowed us to identify it as a nucleoprotein (NP) of lymphocytic choriomeningitis virus (LCMV). Northern blot analysis detected LCMV-specific RNAs in MaTu cells. Comparative immunoprecipitations showed cross-reactivity between NP of LCMV strain WE and MX NP. Using RT-PCR, we have cloned MX NP cDNA. According to sequence comparison, MX LCMV is as closely related to both LCMV strains WE and Armstrong as these strains are to one another. Based on this finding we propose that MX is a new strain of LCMV. We also showed that the stability of MX NP in MaTu cells is very high and that the virus is transmissible by cell-to-cell contact or by cell-free extract to human HeLa and monkey Vero cells, but not to human AGS, canine MDCK, mouse NIH 3T3, and hamster CHO cells. Finally, employing MX LCMV NP in immunoprecipitation and solid-phase radioimmunoassay, we found 37.5% prevalence of anti-LCMV antibodies in human sera, suggesting possible horizontal spread of the virus in the human population.

Immunohistochemical study of colorectal tumors for expression of a novel transmembrane carbonic anhydrase, MN/CA IX, with potential value as a marker of cell proliferation

Carbonic anhydrase isoenzyme IX, MN/CA IX, is a recently discovered member of the carbonic anhydrase (CA) gene family with a suggested function in acid-base balance, intercellular communication, and cell proliferation. Increased expression of MN/CA IX has been observed with certain epithelial tumors. We investigated the expression of MN/CA IX in 69 colorectal neoplasms, consisting of 1 juvenile polyp, 8 hyperplastic polyps, 39 adenomatous lesions, 21 carcinomas, and 7 metastases. Tissue sections were immunostained with a monoclonal antibody specific to MN/CA IX. The proliferative activity of the tumor cells was evaluated by Ki-67 antigen immunoreactivity. The hyperplastic polyps showed a weak or moderate reaction for MN/CA IX only in the cryptal epithelium, as did the normal intestinal mucosa. The adenomas showed immunoreactivity mainly in the superficial part of the mucosa, whereas the distribution in the carcinomas and metastases was more diffuse. Comparative immunostaining of serial sections for Ki-67, a well established marker of cell proliferation, confirmed that MN/CA IX is expressed in areas with high proliferative capacity. Our results show abnormal MN/CA IX expression in colorectal neoplasms, suggesting its involvement in their pathogenesis. The co-occurrence of MN/CA IX and Ki-67 in the same tumor cells indicates its potential for use as a marker of increased proliferation in the colorectal mucosa.

Immunohistochemistry of carbonic anhydrase isozyme IX (MN/CA IX) in human gut reveals polarized expression in the epithelial cells with the highest proliferative capacity

MN/CA IX is a recently discovered member of the carbonic anhydrase (CA) gene family that has been identified in the plasma membranes of certain tumor and epithelial cells and found to promote cell proliferation when transfected into NIH3T3 cells. This study presents localization of MN/CA IX in human gut and compares its distribution to those of CA I, II, and IV, which are known to be expressed in the intestinal epithelium. The specificity of the monoclonal antibody for MN/CA IX was confirmed by Western blots and immunostaining of COS-7 cells transfected with MN/CA IX cDNA. Immunohistochemical stainings of human gut revealed prominent polarized staining for MN/CA IX in the basolateral surfaces of the enterocytes of duodenum and jejunum, the reaction being most intense in the crypts. A moderate reaction was also seen in the crypts of ileal mucosa, whereas the staining became generally weaker in the large intestine. The results indicate isozyme-specific regulation of MN/CA IX expression along the cranial-caudal axis of the human gut and place the protein at the sites of rapid cell proliferation. The unique localization of MN/CA IX on the basolateral surfaces of proliferating crypt enterocytes suggests that it might serve as a ligand or a receptor for another protein that regulates intercellular communication or cell proliferation. Furthermore, MN/CA IX has a completely conserved active site domain of CAs suggesting that it could also participate in carbon dioxide/bicarbonate homeostasis.

MN antigen expression in normal, preneoplastic, and neoplastic esophagus: a clinicopathological study of a new cancer-associated biomarker

Recently, a novel tumor-associated protein, termed MN, has been described in carcinomas of the uterine cervix, where its expression has been shown to be associated with malignant transformation. Because malignant transformation in the esophagus develops through a dysplasia-carcinoma sequence similar to that which occurs in the cervix, this study was performed to evaluate MN expression in normal, preneoplastic, and neoplastic tissues of the esophagus. Esophageal tumor resection specimens from 27 patients (12 squamous cell carcinomas, one multifocal squamous dysplasia, 10 Barrett's-associated adenocarcinomas, two Barrett's esophagus with dysplasia, two adenosquamous carcinomas) were immunohistochemically stained with a monoclonal antibody (clone M75) directed against the MN antigen. The localization of MN antigen, as well as the proportion of positively stained cells, were determined in sections of normal, dysplastic, and carcinomatous tissues. The staining characteristics were correlated with the pathological features of the tumors. Weak intracellular MN expression was detected only in the basal cells of normal squamous epithelium. However, inflamed and reactive squamous epithelium showed increased staining in the basal layer and in the overlying mature squamous cells. MN expression was significantly increased in dysplastic squamous epithelium (P < .001). All esophageal squamous cell carcinomas (100%) stained positively for MN antigen, where the pattern of staining was predominantly membranous. However, the degree of MN staining did not correlate with any of the pathological features of the tumors. In Barrett's epithelium, MN stained positively in all types of metaplastic cells and showed no difference in dysplastic epithelium. In contrast to squamous cell carcinomas, only 80% of esophageal adenocarcinomas were positive for MN, but the degree of MN expression was inversely correlated with histological tumor differentiation (P < .015). The results of this study suggest that (1) the tumor-associated MN antigen may play a role in proliferation and regeneration in esophageal squamous epithelium, and (2) loss of MN expression may be related to cancer progression in Barrett's-associated adenocarcinomas.

Expression of MaTu-MN protein in human tumor cultures and in clinical specimens

MaTu is a novel agent which may be of relevance in human oncogenesis, and has 2 components. One of them, the exogenous MX (coding for protein p58X), is transmissible to human fibroblasts, to HeLa and to HeLa x fibroblast (H/F) hybrids. The other component, MN, is a cellular gene. Its product, the protein p54/58N, is inducible by infecting HeLa cells with MX or by growing them in dense cultures. This p54/58N appears to be a tumor-associated antigen: it is expressed in HeLa and in tumorigenic cells (H/F-T), but not in fibroblasts or in nontumorigenic hybrid cells (H/F-N). Proteins related to p54/58N were also found on immunoblots prepared from human carcinomas of ovary, endometrium and uterine cervix, but not from normal tissues from corresponding organs or from placenta. Using genetically engineered MN protein, we developed a radioimmunoassay for MN-specific antibodies, and for quantitative determination of MN proteins in cell extracts. In HeLa cells infected with MX we observed conspicuous ultrastructural alterations: formation of abundant filaments on the cell surface and amplification of mitochondria. Using immunogold-staining, we visualized the p54/58N on the surface microvilli and in the nucleus, particularly in nucleoli.