Hyperplastic gastric tumors with spasmolytic polypeptide-expressing metaplasia caused by tumor necrosis factor-alpha-dependent inflammation in cyclooxygenase-2/microsomal prostaglandin E synthase-1 transgenic mice

We showed recently that Helicobacter infection induces expression of cyclooxygenase-2 and microsomal prostaglandin E synthase-1 in the mouse stomach, and that transgenic mice expressing both cyclooxygenase-2 and microsomal prostaglandin E synthase-1 (K19-C2mE mice) develop hyperplastic gastric tumors with inflammatory histopathology. To investigate possible roles of proinflammatory cytokines and acquired immunity in the gastric hyperplasia of K19-C2mE mice, we introduced knockout mutations for tumor necrosis factor-alpha (TNF-alpha; Tnf), interleukin-1 receptor-alpha chain (Il1r1), and Rag2 genes, respectively. Among the compound mutants, only the Tnf (-/-) K19-C2mE mice showed significant suppression of hyperplastic tumors with reduced cell proliferation. In contrast, tumorigenesis remained unaffected in either compound mutants of K19-C2mE containing Il1r1 or Rag2 mutation, indicating that neither interleukin-1beta signaling nor T cell/B cell response was required for the development of hyperplastic tumors. Importantly, spasmolytic polypeptide/trefoil factor 2-expressing metaplasia (SPEM) in the K19-C2mE stomach was also suppressed in the Tnf (-/-) K19-C2mE mice, indicating that TNF-alpha-dependent inflammation is responsible for SPEM development. Because gastric metaplasia to the SPEM lineage is considered as a preneoplastic lesion of gastric cancer, it is possible that inhibition of TNF-alpha-dependent inflammation, together with eradication of Helicobacter, can be an effective prevention strategy for gastric cancer.     

Bone marrow-derived cells contribute to NDEA-induced lung squamous cell carcinoma

Bone marrow-derived stem cells (BMDCs) have the ability to differentiate into lung epithelial cells in response to damage; however, their role in squamous cell carcinoma (SCC) formation is unknown. This study aimed to determine whether BMDC-derived lung epithelial cells could contribute to SCC formation. A model of lung SCC induced with N-nitrosodiethylamine (NDEA) in recipient female mice transplanted with green fluorescent protein (GFP)-positive BMDCs from male donors was established. Incorporation of BMDCs in lung tissue was determined using immunohistochemistry and immunofluorescence to detect GFP expression and fluorescence in situ hybridization to Y chromosomes. BMDC appeared at three stages of lung SCC progression: metaplasia, dysplasia, and carcinoma. There was a significantly higher proportion of GFP-positive (GFP⁺) cells within SCC than was found in metaplasia and dysplasia 16 weeks post-transplantation (both P?<?0.017); GFP⁺ BMDCs were also observed in clusters within several SCC nests. Furthermore, most GFP⁺ cells in SCC were pancytokeratin-positive (PCK⁺) epithelial cells, and some exhibited proliferative activity as determined by Ki67 staining (9.7?±?3.92 %). The presence of GFP⁺Ki67⁺PCK⁺ cells within SCC nests suggested that some donor BMDCs differentiated into proliferating epithelial cells. Finally, analysis of p63 expression, a marker of SCC cells, indicated that the presence of GFP⁺p63⁺ cells (green) in inner parts of the SCC. These findings strongly suggest that BMDC-derived lung epithelial cells could participate in lung SCC formation and partially contribute to tumor growth, which might have significant potential implications for both clinical cancer therapy using BMDCs.     

Myeloid suppressor cells regulate the lung environment--letter

4T1 murine mammary carcinoma cells implanted in syngeneic Balb/c mice are increasingly being used in metastasis research, with some groups using this model to study tumor-induced accumulation of bone marrow-derived cells in metastatic target organs. Bone marrow-derived cells (including CD11b(+)Gr-1(+) myelomonocytic cells) are thought to modify the local lung microenvironment to facilitate subsequent colonization by metastatic tumor cells. While quantification of metastatic 4T1 tumor cells in various tissues can be done using ex vivo colony-forming assays, detection of metastatic 4T1 cells is often facilitated by expressing fluorescent proteins in the tumor cells prior to implantation. We found that Balb/c mice mount a potent immune response against 4T1 cells expressing green fluorescent protein (GFP) that includes the generation of anti-GFP antibodies in the circulation. Importantly, the number of bone marrow-derived CD11b(+)Gr-1(+) cells and metastatic tumor cells that accumulate in the lungs is significantly decreased in mice implanted with 4T1 cells expressing GFP compared with mice bearing wild-type 4T1 tumors. Taken together, our data caution against the use of GFP-expressing tumor cells in the Balb/c mouse strain, particularly for studying the influence of immunomodulatory cells on tumor cell metastasis.     

Swedish moist snuff accelerates gastric cancer development in Helicobacter pylori-infected wild-type and gastrin transgenic mice

The Swedish variant of moist oral smokeless tobacco (snus) is popular in Sweden and Norway, banned from sale within the European Union and is currently being introduced in USA. The aim of the present study was to determine if snus is carcinogenic to the stomach, particularly in Helicobacter pylori (H.P.)-infected hosts at increased risk for gastric cancer development. Snus (Generaltrade mark; Swedish Match, Sweden) was mixed with powdered standard mouse chow at a concentration of 5-9% (wt/wt) and given to wild-type (WT, FVB) and gastrin transgenic (INS-GAS, FVB) mice for 6 months with or without H.P. (strain 67:21, CagA+, VacA+) infection. At necropsy, pathological evaluation of stomachs from uninfected snus-treated WT mice showed mild morphological changes, whereas 50% snus-treated INS-GAS mice developed carcinoma in situ (CIS), compared with 25% not exposed to snus. When snus was given to H.P.-infected mice, 9 of 17 WT mice developed CIS with intramucosal invasion, and the remaining 8 of 17 WT mice developed high-grade dysplasia (score >1.5) that was associated with increased gastritis, epithelial defects, oxyntic atrophy, hyperplasia and intestinal metaplasia. Twelve of 12 H.P.-infected INS-GAS mice developed CIS with intramucosal invasion and submucosal herniation. We suggest that snus is a potential gastric carcinogen in mice. The development of CIS was associated with increased rates of the epithelial cell proliferation and apoptosis, common features of gastric carcinogenesis.     

豫西地区胃黏膜不典型增生和肠化生的临床流行病学调查

目的：探讨近4年豫西地区胃黏膜不典型增生和肠化生的相关临床流行病学资料的特点及变化趋势。方法：选取2007年1月-2010年6月我院胃镜室行内镜检查的21932例患者为研究对象,对胃黏膜不典型增生和肠化生患者的一般临床资料和病理资料进行回顾性分析。结果：胃黏膜不典型增生和不典型增生伴肠化生有随年龄增加检出率增高的趋势,且不典型增生程度随年龄增加而程度增高。重度不典型增生≥60岁患者比例高于轻、中度不典型增生,（P〈0.05）,中度不典型增生≥60岁患者比例高于轻度不典型增生;中度肠化生≥60岁患者比例高于轻度肠化生患者（P〈0.05）。贲门部不典型增生和肠化生中≥60岁患者比例高于胃角和胃体部（P〈0.05）,幽门螺杆菌检出率均较单纯慢性浅表性胃炎组高,（P〈0.05）差异有统计学意义。结论：胃黏膜不典型增生和肠化生的发生与年龄和幽门螺杆菌感染有关,常发生于贲门部。     

Loss of E-cadherin in mouse gastric epithelial cells induces signet ring-like cells, a possible precursor lesion of diffuse gastric cancer

Alterations in the E-cadherin gene are associated with sporadic and hereditary diffuse-type gastric cancer. To determine how the loss of function of E-cadherin affects gastric epithelial cell phenotypes, we generated transgenic mice using the Cre-loxP system in which the E-cadherin gene is specifically knocked out in the parietal cell lineage. In the transgenic mice, expression of E-cadherin was lost or reduced in proton pump-expressing parietal cells, which became round in shape and were pushed out of the glands to accumulate in the stromal area. Additionally, gastric mucosa exhibited hyperplasia from 3 months in the mice, some cells of which later became positive for trefoil factor 2, a marker of spasmolytic polypeptide-expressing metaplasia. From 6 months, E-cadherin-negative/proton pump-negative cells appeared from the parietal cell lineage, which increased in number to form cell clusters. Moreover, signet ring-like cells, which are morphologically similar to signet ring carcinoma cells, were found in the cell clusters from 12 months. However, no invasive gastric adenocarcinomas were found in the E-cadherin-deficient mice, even at 24 months or later. These data indicate that the loss of E-cadherin induces possible pre-cancerous lesions in the gastric mucosa but may not be sufficient for its malignant conversion.     

豫西地区胃黏膜不典型增生和肠化生的临床流行病学调查

目的:探讨近4年豫西地区胃黏膜不典型增生和肠化生的相关临床流行病学资料的特点及变化趋势。方法:选取2007年1月-2010年6月我院胃镜室行内镜检查的21932例患者为研究对象,对胃黏膜不典型增生和肠化生患者的一般临床资料和病理资料进行回顾性分析。结果:胃黏膜不典型增生和不典型增生伴肠化生有随年龄增加检出率增高的趋势,且不典型增生程度随年龄增加而程度增高。重度不典型增生≥60岁患者比例高于轻、中度不典型增生,(P<0.05),中度不典型增生≥60岁患者比例高于轻度不典型增生;中度肠化生≥60岁患者比例高于轻度肠化生患者(P<0.05)。贲门部不典型增生和肠化生中≥60岁患者比例高于胃角和胃体部(P<0.05),幽门螺杆菌检出率均较单纯慢性浅表性胃炎组高,(P<0.05)差异有统计学意义。结论:胃黏膜不典型增生和肠化生的发生与年龄和幽门螺杆菌感染有关,常发生于贲门部。     

Sensitivity of the cervical transformation zone to estrogen-induced squamous carcinogenesis

Regions where one type of epithelium replaces another (metaplasia) have a predilection for cancer formation. Environmental factors are closely linked to metaplastic carcinogenesis. In particular, cervical cancers associated with human papillomavirus (HPV) infection develop primarily at the transformation zone, a region where metaplastic squamous cells are detected in otherwise columnar epithelial-lined endocervical glands. Previously, we reported estrogen-induced multistage vaginal and cervical carcinogenesis in transgenic mice expressing HPV16 oncogenes in basal squamous epithelial cells. In the present study to investigate the threshold neoplastic response to exogenous estrogen, we treated groups of transgenic mice with lower hormone doses. A 5-fold reduction in estrogen dose induced squamous carcinogenesis solely at the cervical transformation zone compared with other reproductive tract sites. Further study delineated stages of transformation zone carcinogenesis, including formation of hyperplastic lower uterine glands and emergence of multiple foci of squamous metaplasia from individual stem-like glandular reserve cells, followed by neoplastic progression of metaplasia to dysplasia and squamous cancer. We propose that a combination of low-dose estrogen and low-level HPV oncogene expression biases transformation zone glandular reserve cells toward squamous rather than columnar epithelial fate decisions. Synergistic activation of proliferation by viral oncoprotein cell cycle dysregulation and estrogen receptor signaling, together with altered paracrine stromal-epithelial interactions, may conspire to support and promote neoplastic progression and cancer formation.     

Myeloid progenitor cells in the premetastatic lung promote metastases by inducing mesenchymal to epithelial transition

Tumors systemically initiate metastatic niches in distant target metastatic organs. These niches, composed of bone marrow-derived hematopoietic cells, provide permissive conditions for future metastases. However, the mechanisms by which these cells mediate outgrowth of metastatic tumor cells are not completely known. Using mouse models of spontaneous breast cancer, we show enhanced recruitment of bone marrow-derived CD11b(+)Gr1(+) myeloid progenitor cells in the premetastatic lungs. Gene expression profiling revealed that the myeloid cells from metastatic lungs express versican, an extracellular matrix proteoglycan. Notably, versican in metastatic lungs was mainly contributed by the CD11b(+)Ly6C(high) monocytic fraction of the myeloid cells and not the tumor cells or other stromal cells. Versican knockdown in the bone marrow significantly impaired lung metastases in vivo, without impacting their recruitment to the lungs or altering the immune microenvironment. Versican stimulated mesenchymal to epithelial transition of metastatic tumor cells by attenuating phospho-Smad2 levels, which resulted in elevated cell proliferation and accelerated metastases. Analysis of clinical specimens showed elevated versican expression within the metastatic lung of patients with breast cancer. Together, our findings suggest that selectively targeting tumor-elicited myeloid cells or versican represents a potential therapeutic strategy for combating metastatic disease.     

IFN-γ inhibits gastric carcinogenesis by inducing epithelial cell autophagy and T-cell apoptosis

IFN-γ mediates responses to bacterial infection and autoimmune disease, but it is also an important tumor suppressor. It is upregulated in the gastric mucosa by chronic Helicobacter infection; however, whether it plays a positive or negative role in inflammation-associated gastric carcinogenesis is unexplored. To study this question, we generated an H(+)/K(+)-ATPase-IFN-γ transgenic mouse that overexpresses murine IFN-γ in the stomach mucosa. In contrast to the expected proinflammatory role during infection, we found that IFN-γ overexpression failed to induce gastritis and instead inhibited gastric carcinogenesis induced by interleukin-1beta (IL-1β) and/or Helicobacter infection. Helper T cell (Th) 1 and Th17 immune responses were inhibited by IFN-γ through Fas induction and apoptosis in CD4 T cells. IFN-γ also induced autophagy in gastric epithelial cells through increased expression of Beclin-1. Finally, in the gastric epithelium, IFN-γ also inhibited IL-1β- and Helicobacter-induced epithelial apoptosis, proliferation, and Dckl1(+) cell expansion. Taken together, our results suggest that IFN-γ coordinately inhibits bacterial infection and carcinogenesis in the gastric mucosa by suppressing putative gastric progenitor cell expansion and reducing epithelial cell apoptosis via induction of an autophagic program.     

Helicobacter pylori but not high salt induces gastric intraepithelial neoplasia in B6129 mice

Helicobacter pylori is responsible for most human stomach cancers. Gastric cancer also is overrepresented in populations consuming high-salt diets. Attempts to test the hypothesis that high salt promotes H. pylori carcinogenesis have been hindered by the lack of a wild-type mouse model. Based on pilot observations of unexpectedly early gastric adenocarcinoma in C57BL/6 x 129S6/SvEv (B6129) mice infected with Helicobacter felis, we conducted a study to characterize H. pylori infection in these mice and to determine whether high salt promotes tumorigenesis. Male and female mice were gavaged with H. pylori Sydney strain-1 or vehicle only and divided into four groups based on infection status and maintenance on a basal (0.25%) or high (7.5%) salt diet. In uninfected mice, the high-salt diet enhanced proliferation and marginally increased parietal cell mucous metaplasia with oxyntic atrophy. Lesions in H. pylori infected mice without regard to diet or gender were of equivalent severity and characterized by progressive gastritis, oxyntic atrophy, hyperplasia, intestinal metaplasia, and dysplasia. Infected mice on the high-salt diet exhibited a shift in antimicrobial humoral immunity from a Th1 to a Th2 pattern, accompanied by significantly higher colonization and a qualitative increase in infiltrating eosinophils. No mice developed anti-parietal cell antibodies suggestive of autoimmune gastritis. At 15 months of age infected mice in both dietary cohorts exhibited high-grade dysplasia consistent with gastric intraepithelial neoplasia. In summary, we report for the first time H. pylori-induced gastric intraepithelial neoplasia in a wild-type mouse model and show no additive effect of high-salt ingestion on tumor progression.     

Columnar metaplasia in a surgical mouse model of gastro‐esophageal reflux disease is not derived from bone marrow‐derived cell

The incidence of esophageal adenocarcinoma has increased in the last 25 years. Columnar metaplasia in Barrett's mucosa is assumed to be a precancerous lesion for esophageal adenocarcinoma. However, the induction process of Barrett's mucosa is still unknown. To analyze the induction of esophageal columnar metaplasia, we established a mouse gastro‐esophageal reflux disease (GERD) model with associated development of columnar metaplasia in the esophagus. C57BL/6 mice received side‐to‐side anastomosis of the esophagogastric junction with the jejunum, and mice were killed 10, 20, and 40 weeks after operation. To analyze the contribution of bone marrow‐derived cells to columnar metaplasia in this surgical GERD model, some mice were transplanted with GFP‐marked bone marrow after the operation. Seventy‐three percent of the mice (16/22) showed thickened mucosa in esophagus and 41% of mice (9/22) developed columnar metaplasia 40 weeks after the operation with a mortality rate of 4%. Bone marrow‐derived cells were not detected in columnar metaplastic epithelia. However, scattered epithelial cells in the thickened squamous epithelia in regions of esophagitis did show bone marrow derivation. The results demonstrate that reflux induced by esophago‐jejunostomy in mice leads to the development of columnar metaplasia in the esophagus. However, bone marrow‐derived cells do not contribute directly to columnar metaplasia in this mouse model.     

Direct and indirect contribution of bone marrow‐derived cells to cancer

Stromal‐epithelial interactions may control the growth and initiation of cancers. Here, we not only test the hypothesis that bone marrow‐derived cells may effect development of cancers arising from other tissue cells by forming tumor stroma but also that sarcomas may arise by transformation of stem cells from the bone marrow and epithelial cancers may arise by transdifferentiation of bone marrow stem cells to epithelial cancers. Lethally irradiated female FVB/N mice were restored with bone marrow (BM) transplants from a male transgenic mouse carrying the polyoma middle T‐oncoprotein under the control of the mouse mammary tumor virus promoter (MMTV‐PyMT) and followed for development of lesions. All of 8 lethally irradiated female FVB/N recipient mice, restored with BM transplants from a male MMTV‐PyMT transgenic mouse, developed Y‐chromosome negative (Y−) cancers of various organs surrounded by Y+ stroma. One of the female FVB/N recipient mice also developed fibrosarcoma and 1, a diploid breast adenocarcinoma containing Y chromosomes. In contrast, only 1 of 12 control female mice restored with normal male BM developed a tumor (lymphoma) during the same time period. These results indicate not only that the transgenic BM‐derived stromal cells may indirectly contribute to development of tumors in recipient mice but also that sarcomas may arise by transformation of BM stem cells and that breast cancers arise by transdifferentiation of BM stem cells, presumably by mesenchymal‐epithelial transition.     

Heterotopic endochondrial ossification with mixed tumor formation in C3(1)/Tag transgenic mice is associated with elevated TGF-beta1 and BMP-2 expression.

Transgenic mice which express the simian virus 40 large T-antigen (Tag) under the regulatory control of the hormone responsive rat C3(1) gene develop unusual lesions of heterotopic bone growth associated with mixed tumor formation arising from eccrine sweat glands found only in the foot pads of mice, ischiocavernosus muscle adjacent to bulbourethral glands and occasionally the salivary and mammary glands. These lesions are very similar to mixed tumors arising in several types of human cancers. Based upon electron microscopic examination and immunocytochemical analyses of cellular differentiation markers, the mixed proliferative lesions in this transgenic mouse model begin with the Tag-induced proliferation of epithelial and myoepithelial cells. The proliferation of these two types of cells results in hyperplasia and adenomatous transformation of the epithelial component, whereas the proliferating myoepithelial cells undergo metaplasia to form chondrocytes which deposit extracellular matrix, including collagen fibers. Cartilage develops focally between areas of epithelial proliferation and subsequently ossifies through a process of endochondrial bone formation. The metaplasia of myoepithelial cells to chondrocytes appears to require the inductive interaction of factors produced by the closely associated proliferating epithelial cells, including members of the TGF-beta superfamily. We demonstrate that TGF-beta1 protein accumulates in the extracellular matrix of the lesions, whereas RNA in situ hybridization reveals that BMP-2, another strong inducer of heterotopic bone formation, is overexpressed by the proliferating epithelial cells during the development of ectopic bone. The formation of sarcomatous tumors within the mixed tumors appears to be androgen-dependent and more frequent in mice lacking a normal allele of p53. This process of cartilage and bone induction may mimic epithelial-mesenchymal interactions which occur during embryonic bone formation. These transgenic mice may provide new insights into the processes of ectopic endochondrial bone formation associated with mixed tumor formation and serve as a useful model for human heterotopic bone disease.     

Cysteine-rich fibroblast growth factor receptor 1, a new marker for precancerous epithelial lesions defined by the human monoclonal antibody PAM-1

Precancerous epithelial lesions are sites of uncontrolled cellular proliferation, generated by irreversible genetic changes. Not all of these lesions progress to invasive cancer, some may even regress, but early detection of abnormal cells can be crucial for survival of the patient. Diagnosis is mainly performed by using morphological parameters. Proliferation markers can facilitate the analysis, if they show a consistent expression, and distinguish between healthy and malignant cells. The fully human monoclonal IgM antibody PAM-1 was isolated from a patient with stomach carcinoma and binds to a new variant of cysteine-rich fibroblast growth factor receptor 1 (CFR-1). This CFR-1/PAM-1 receptor is expressed on nearly all of the epithelial cancers of every type and origin, but not on healthy tissue. It is also present on precursor lesions found in: Helicobacter pylori-induced gastritis, intestinal metaplasia and dysplasia of the stomach, ulcerative colitis-related dysplasia and adenomas of the colon, Barrett's metaplasia and dysplasia of the esophagus, squamous cell metaplasia and dysplasia of the lung, and cervical intraepithelial neoplasia. The unique, growth-dependent expression of this new CFR-1 isoform makes the PAM-1 antibody an ideal diagnostic tool for the detection of precancerous and cancerous lesions.     

Co-operation between follicular ornithine decarboxylase and v-Ha-ras induces spontaneous papillomas and malignant conversion in transgenic skin

Ornithine decarboxylase (ODC) is aberrantly regulated in tumor cells and results in high basal levels of ODC and polyamines in many epithelial tumors. To determine if elevated ODC/polyamine levels can co- operate with a mutant Ha-ras gene in mouse skin tumorigenesis, double transgenic mice were generated by breeding K6/ODC transgenic mice with TG.AC v-Ha-ras transgenic mice. A K6 keratin promoter drives the ODC transgene in K6/ ODC transgenic mice, which results in elevated ODC/ polyamine levels directed to the outer root sheath cells of hair follicles. TG.AC transgenic mice carry a v-Ha-ras transgene while still retaining two normal c-Ha-ras alleles. Transgenic mice that possess only the K6/ODC or the v-Ha-ras transgene did not develop tumors unless treated with either a carcinogen or a tumor promoter, respectively. However, a high percentage of double transgenic mice possessing both the K6/ODC and v-Ha-ras transgenes developed spontaneous tumors. All tumors were well-differentiated keratoacanthomas, some of which progressed to carcinomas within 2 months. The development and the maintenance of these ODC/ras tumors was ODC-dependent since alpha- difluoromethylornithine (DFMO), a specific ODC inhibitor, prevented the formation and caused the regression of these tumors. These findings indicate that ODC overexpression and an activated Ha-ras are sufficient to produce a high rate of malignant transformation in an animal model. The ODC/ras double transgenic mouse provides a simple in vivo model without the use of chemical carcinogens or tumor promoters in which to test downstream effectors that play a key role in mediating the development of epithelial tumors resulting from the cooperation between ODC and v-Ha-ras.      

CD4(+)CD25(+) regulatory lymphocytes require interleukin 10 to interrupt colon carcinogenesis in mice

Roles for host immune response in carcinogenesis are not well defined. Recent studies have shown that microbially driven inflammation can lead to colon cancer and that prior transfer of regulatory lymphocytes expressing CD4 and CD25 prevents the innate inflammatory events that lead to colon cancer in mice. To further examine the ability of regulatory lymphocytes to inhibit carcinogenesis, 129/SvEv Rag-2-deficient mice were inoculated by gastric gavage with Helicobacter hepaticus, an enteric bacterial pathogen of mice. Mice were then treated at 1, 3, or 12 months after infection with adoptive transfer of CD4(+)CD45RB(lo)CD25(+)-regulatory cells. Mice dosed with regulatory cells at 4 or 12 weeks after H. hepaticus infection had reduced severity of inflammatory bowel disease and significantly lower risk of colon cancer during the 8 month observation period, compared with infected mice that had not received cells. This suggested that regulatory cells were able to interrupt the ongoing innate immune events in the stepwise progression to cancer. Transfer of regulatory cells into chronically infected mice with established cancer reduced severity of colitis, epithelial dysplasia, and cancer, but did not eliminate all tumors. Regulatory cells lacking anti-inflammatory cytokine interleukin (IL)-10 were unable to inhibit inflammatory bowel disease, dysplasia, or cancer, showing that IL-10 was required for the protective effects of lymphocytes in this setting. Taken together, the data suggest that IL-10-mediated suppression of host innate inflammatory response was pivotal in interrupting carcinogenesis. Regulatory lymphocytes and cytokines may have implications for novel therapies for colon cancer in humans.     

K-ras mutations and HLA-DR expression in large bowel adenomas.

A total of 72 sporadic colorectal adenomas in 56 patients were studied for the presence of point mutations in codons 12 and 13 of the K-ras gene and for HLA-DR antigen expression related to clinicopathological variables. Forty K-ras mutations in 39 adenomas were found (54%): 31 (77%) in codon 12 and nine (23%) in codon 13. There was a strong relationship between the incidence of K-ras mutations and adenoma type, degree of dysplasia and sex. The highest frequency of K-ras mutations was seen in large adenomas of the villous type with high-grade dysplasia. Fourteen out of 15 adenomas obtained from 14 women above 65 years of age carried mutations. HLA-DR positivity was found in 38% of the adenomas, large tumours and those with high-grade dysplasia having the strongest staining. Coexpression of K-ras mutations and HLA-DR was found significantly more frequently in large and highly dysplastic adenomas, although two-way analysis of variance showing size and grade of dysplasia to be the most important variable. None of the adenomas with low-grade dysplasia showed both K-ras mutation and HLA-DR positivity (P = 0.004). K-ras mutation is recognised as an early event in colorectal carcinogenesis. The mutation might give rise to peptides that may be presented on the tumour cell surface by class II molecules, and thereby induce immune responses against neoplastic cells.