Expression of vascular endothelial growth factor by macrophages is up-regulated in poorly vascularized areas of breast carcinomas

Angiogenesis is essential to the growth and metastasis of solid tumours. Vascular endothelial growth factor (VEGF) is a potent pro-angiogenic cytokine that is overexpressed in malignant tumours such as invasive carcinoma of the breast. The low oxygen tensions (hypoxia) present in these tumours are known to up-regulate the expression of VEGF by tumour cells. Human macrophages also respond to hypoxia by increasing their release of VEGF in vitro, although the effect of hypoxia on VEGF expression by macrophages in vivo has yet to be demonstrated. The present study compared the expression of VEGF by macrophages in areas of low and high vascularity in 24 invasive breast carcinomas (12 lobular, 12 ductal). The cellular distributions of VEGF protein, CD31 (vessels), and CD68 (macrophages) were compared in sequential sections for each tumour. In ten tumours, both tumour cells and macrophages were immunoreactive for VEGF protein. Use of non-isotopic in situ hybridization to localize VEGF mRNA showed that these cell types also expressed VEGF mRNA. No significant differences in the cellular distribution of VEGF protein were found between lobular and ductal carcinomas. In all tumours, macrophages accumulated in higher numbers in poorly vascularized than in highly vascularized areas. In VEGF-positive tumours, macrophages were immunoreactive for VEGF only in avascular areas where tumour cells also expressed VEGF. This suggests that VEGF expression by these two cell types may be regulated by the same microenvironmental stimuli in breast carcinomas. In addition, significantly more macrophages were present in poorly vascularized areas of VEGF-positive than VEGF-negative tumours. This suggests that VEGF may exert a chemotactic action on macrophages in vivo and guide their migration into avascular tumour sites.

Expression of vascular endothelial growth factor by macrophages is up-regulated in poorly vascularized areas of breast carcinomas

Angiogenesis is essential to the growth and metastasis of solid tumours. Vascular endothelial growth factor (VEGF) is a potent pro-angiogenic cytokine that is overexpressed in malignant tumours such as invasive carcinoma of the breast. The low oxygen tensions (hypoxia) present in these tumours are known to up-regulate the expression of VEGF by tumour cells. Human macrophages also respond to hypoxia by increasing their release of VEGF in vitro, although the effect of hypoxia on VEGF expression by macrophages in vivo has yet to be demonstrated. The present study compared the expression of VEGF by macrophages in areas of low and high vascularity in 24 invasive breast carcinomas (12 lobular, 12 ductal). The cellular distributions of VEGF protein, CD31 (vessels), and CD68 (macrophages) were compared in sequential sections for each tumour. In ten tumours, both tumour cells and macrophages were immunoreactive for VEGF protein. Use of non-isotopic in situ hybridization to localize VEGF mRNA showed that these cell types also expressed VEGF mRNA. No significant differences in the cellular distribution of VEGF protein were found between lobular and ductal carcinomas. In all tumours, macrophages accumulated in higher numbers in poorly vascularized than in highly vascularized areas. In VEGF-positive tumours, macrophages were immunoreactive for VEGF only in avascular areas where tumour cells also expressed VEGF. This suggests that VEGF expression by these two cell types may be regulated by the same microenvironmental stimuli in breast carcinomas. In addition, significantly more macrophages were present in poorly vascularized areas of VEGF-positive than VEGF-negative tumours. This suggests that VEGF may exert a chemotactic action on macrophages in vivo and guide their migration into avascular tumour sites.

What levels of agreement can be expected between histopathologists assigning cases to discrete nominal categories? A study of the diagnosis of hyperplastic and adenomatous colorectal polyps

AIMS

To assess the levels of agreement between histopathologists for a two-class nominal categorization process--the discrimination between hyperplastic and adenomatous colorectal polyps.

METHODS

Fifty hyperplastic and 50 adenomatous polyps received consecutively in the laboratory were categorized by nine histopathologists, and the level of agreement between all observers and the original diagnosis was assessed using kappa statistics.

RESULTS

For the eight observers with 11 months or more experience in histopathology, there was a high level of agreement with kappa statistics ranging from 0.84 to 0.98. This process was performed rapidly with an average of 13 to 22 seconds spent on each case. One observer with only 6-weeks' experience of histopathology had a lower overall level of agreement with kappa statistics ranging from 0.46 to 0.54, but the performance on the later cases was much higher.

CONCLUSIONS

The level of agreement in the distinction between hyperplastic and adenomatous colorectal polyps is high among histopathologists with at least moderate amounts of experience in histopathology. The one virtually naïve observer showed a marked learning response during the study without feedback on case outcome. This suggests that histopathologists are very reliable in assigning cases to distinct nominal categories and that learning of these processes occurs early in a histopathologist's career.

Macrophage infiltration is associated with VEGF and EGFR expression in breast cancer

Angiogenesis is esential for tumour growth and metastasis. Vascular endothelial growth factor (VEGF) is a potent endothelial cell mitogen and is an important component of the angiogenic stimulus in a range of human neoplasias. In addition to its mitogenic activities, VEGF has also been found to stimulate migration in macrophages via the flt-1 VEGF receptor. It has previously been shown that increased focal tumour macrophage infiltration is associated with increased angiogenesis and worsened relapse-free and overall survival in breast cancer. Macrophages are able to stimulate angiogenesis by their production of a range of factors including VEGF, tumour necrosis factor-alpha (TNF-alpha), and thymidine phosphorylase (TP). Thus, in breast cancer, VEGF could have a dual role in the regulation of angiogenesis, by direct mitogenic stimulation of endothelial cells, and also indirectly by attracting macrophages into avascular tumours. The purpose of this study was to localize VEGF protein in a series of 96 consecutive primary breast carcinomas and to determine its relationship to focal macrophage infiltration (macrophage index). These two variables were also compared with the pathological features of the tumours, as well as oestrogen receptor (ER), epidermal growth factor receptor (EGFR), microvessel density, macrophage index, and survival. An inverse relationship (p=0.0006) was noted between VEGF and EGFR, with high VEGF expression correlating with low EGFR levels. In the EGFR-negative group of cases (n=56), positive associations were observed between VEGF expression and macrophage index (p=0.005), ER (p=0.05), p53 (p=0. 006), tumour grade (p=0.02), and tumour necrosis (p=0.03). Macrophage counts were higher in EGFR-positive tumours (p=0.0006) and no associations were found between VEGF expression and increased microvessel density. These results show that in breast cancers there are two types of macrophage infiltrates, one associated with the presence of EGFR and low VEGF expression in tumours and the other with high VEGF expression in EGFR-negative tumours. VEGF expression may be an important factor in the recruitment of tumour-associated macrophages into breast carcinomas and may thus have an additional, indirect, pathway of angiogenic stimulation in this type of tumour.

Macrophage infiltration is associated with VEGF and EGFR expression in breast cancer

Angiogenesis is esential for tumour growth and metastasis. Vascular endothelial growth factor (VEGF) is a potent endothelial cell mitogen and is an important component of the angiogenic stimulus in a range of human neoplasias. In addition to its mitogenic activities, VEGF has also been found to stimulate migration in macrophages via the flt-1 VEGF receptor. It has previously been shown that increased focal tumour macrophage infiltration is associated with increased angiogenesis and worsened relapse-free and overall survival in breast cancer. Macrophages are able to stimulate angiogenesis by their production of a range of factors including VEGF, tumour necrosis factor-alpha (TNF-alpha), and thymidine phosphorylase (TP). Thus, in breast cancer, VEGF could have a dual role in the regulation of angiogenesis, by direct mitogenic stimulation of endothelial cells, and also indirectly by attracting macrophages into avascular tumours. The purpose of this study was to localize VEGF protein in a series of 96 consecutive primary breast carcinomas and to determine its relationship to focal macrophage infiltration (macrophage index). These two variables were also compared with the pathological features of the tumours, as well as oestrogen receptor (ER), epidermal growth factor receptor (EGFR), microvessel density, macrophage index, and survival. An inverse relationship (p=0.0006) was noted between VEGF and EGFR, with high VEGF expression correlating with low EGFR levels. In the EGFR-negative group of cases (n=56), positive associations were observed between VEGF expression and macrophage index (p=0.005), ER (p=0.05), p53 (p=0. 006), tumour grade (p=0.02), and tumour necrosis (p=0.03). Macrophage counts were higher in EGFR-positive tumours (p=0.0006) and no associations were found between VEGF expression and increased microvessel density. These results show that in breast cancers there are two types of macrophage infiltrates, one associated with the presence of EGFR and low VEGF expression in tumours and the other with high VEGF expression in EGFR-negative tumours. VEGF expression may be an important factor in the recruitment of tumour-associated macrophages into breast carcinomas and may thus have an additional, indirect, pathway of angiogenic stimulation in this type of tumour.

Necrosis correlates with high vascular density and focal macrophage infiltration in invasive carcinoma of the breast

Necrosis is a common feature of invasive carcinoma of the breast and is caused by chronic ischaemia leading to infarction. Although necrosis was previously assumed to be due to a generally poor blood supply in the tumour, in this study we show that it is present in tumours with focal areas of high vascular density situated away from the actual sites of necrosis. This may account, in part, for the previous observation that necrosis is linked to poor prognosis in this disease. Highly angiogenic tumours often display blood vessel shunting from one tumour area to another, which further exacerbates ischaemia and the formation of tumour necrosis. We have recently demonstrated that high focal microphage infiltration into breast tumours is significantly associated with increased tumour angiogenesis and poor prognosis and that the macrophages accumulate in poorly vascularized, hypoxic areas within breast tumours. In order to investigate the interactions of macrophages with chronic ischaemia (as reflected by the presence of necrosis) and angiogenesis in breast tumours, we quantified the levels of these three biological parameters in a series of 109 consecutive invasive breast carcinomas. We found that the degree of tumour necrosis was correlated with both microphage infiltration (Mann-Whitney U, P-value = 0.0009; chi-square, P-value = 0.01) and angiogenesis (Mann-Whitney U P-value = 0.0008, chi square P-value = 0.03). It was also observed that necrosis was a feature of tumours possessing an aggressive phenotype, i.e. high tumour grade (chi-square, P-value < 0.001), larger size (Mann-Whitney U, P-value = 0.003) and low oestrogen receptor status (Mann-Whitney U, P-value = 0.008; chi-square, P-value < 0.008). We suggest, therefore, that aggressive tumours rapidly outgrow their vascular supply in certain areas, leading to areas of prolonged hypoxia within the tumour and, subsequently, to necrosis. This, in turn, may attract macrophages into the tumour, which then contribute to the angiogenic process, giving rise to an association between high levels of angiogenesis and extensive necrosis.

Molecular analysis of ras oncogenes in CIN III and in stage I and II invasive squamous cell carcinoma of the uterine cervix

AIM

To examine the prevalence of genital type human papilloma virus (HPV) and mutations at codons 12, 13, and 61 in H, Ki, and N-ras in CIN III and early invasive squamous cell carcinomas of the cervix.

METHODS

Prevalence of HPV was examined in 20 CIN III and 20 stage I and II cervical carcinomas, using non-isotopic in situ hybridisation (NISH) and solution phase polymerase chain reaction (PCR). In addition, mutations at codons 12, 13, and 61 were examined in H, Ki, and N-ras in these CIN III and early invasive squamous cell carcinomas, to assess the prevalence of ras gene point mutations and to define where in the pathobiology of squamous cell carcinoma such events occur. A non-isotopic PCR/RFLP assay was used to define these mutations.

RESULTS

Of the 20 CIN IIIs examined, 19 contained HPV 16 DNA sequences by PCR and NISH. Dual infection was not uncovered. The 20 early (stage I and II) invasive squamous cell carcinomas showed predominant HPV 16 positivity (17/20), with one case HPV 18 positive, confirmed on PCR and NISH. Activating mutations were not identified in any of the CIN III cases. Only one stage I, HPV 16 positive carcinoma showed an activating mutation in H-ras codon 12, which was not present in adjacent normal ectocervical mucosa from the same patient.

CONCLUSIONS

ras Activation does not appear to occur in conjunction with HPV infection, particularly of HPV 16 infected high grade cervical intraepithelial neoplasia, or to occur commonly in early cervical squamous cell carcinoma. The postulated model of HPV linked carcinogenesis suggests malfunctional control of viral transcription as a necessary component of neoplastic progression. It is also clear that host gene alterations are equally necessary for HPV linked carcinogenesis to occur.

Human papillomavirus and mixed epithelial tumors of the endometrium

Strong epidemiological evidence links human papilloma viruses (HPV) with the development of cervical intraepithelial neoplasia (CIN) and invasive cancers of the uterine cervix. The localization of HPV DNA sequences high up in the female genital tract (in benign and malignant lesions) is not that uncommon, but its precise significance is uncertain. In particular, the detection of HPV DNA sequences by polymerase chain reaction (PCR) needs careful interpretation, because the source of the amplicon may emanate from tumor cells, direct contamination from the cervix, or possibly from extratumoral sites in the endometrium. We have previously reported the identification of koilocyte-like changes in the squamous epithelium of some endometrial adenoacanthomas. Adenoacanthomas (adenocarcinoma with squamous metaplasia) are mixed epithelial tumors arising in the endometrium composed of malignant glandular areas admixed with benign metaplastic squamous epithelium. The rarer adenosquamous carcinoma containing both malignant glandular and squamous areas is also described. The origin of benign/malignant squamous epithelial islands in endometrial tumors has been the subject of speculation, with some investigators considering an origin from metaplastic glandular endometrial cells. In this study, we examined 10 normal endometrial samples, 20 adenocarcinomas, 41 adenocarcinomas with squamous metaplasia, and two adenosquamous carcinomas, (including control cervical material where possible) for the presence of HPV DNA sequences using nonisotopic in situ hybridization (NISH), type-specific HPV PCR, general primer PCR (to detect sequenced and unsequenced HPVs), and PCR in situ hybridization (PCR-ISH). We did not identify HPV DNA sequences in normal endometrial tissue. In adenocarcinomas (endometrioid type), HPV was only identified in 2 of 20 cases by PCR, both of which were HPV 11 positive. We were unsuccessful in identifying HPV in endometrial carcinomas by NISH or by PCR-ISH, raising the possibility of contamination from the cervix in the two positive cases. In adenoacanthomas, a low-risk HPV type (HPV 6) was found in 19 of 41 cases. NISH signals were intranuclear in location in squamous regions of adenoacanthomas. Additional positive nuclei were uncovered using PCR-ISH, which increases the sensitivity of standard NISH detection. HPV DNA sequences were located in some malignant endometrial glandular epithelial cells, but this accounted for a minority of samples. HPV DNA sequences were not detected in extraepithelial sites. Mixed infection by two different HPV types was identified in two cases. Most cases showed similar HPV types in cervical and endometrial lesions, although discordant cases were uncovered. In adenosquamous carcinomas, one case showed mixed infection with HPV 6 and 33 by PCR. The apparent segregation of low-risk HPV type (HPV 6) with benign squamous metaplastic epithelium in adenocarcinoma with squamous metaplasia, and high-risk type (HPV 33) with malignant squamous epithelium in adenosquamous carcinoma, raises important questions in relation to the role of HPVs in mixed epithelial tumors of the endometrium and their interplay in the pathogenesis of squamous metaplasia at extracervical sites.

Alterations in exon 1 of c-myc and expression of p62c-myc in cervical squamous cell carcinoma

AIMS

To examine human papillomavirus (HPV) positive and negative squamous cell carcinomas of the cervix for structural alterations in exon 1 c-myc; and to investigate the expression pattern of p62, the protein product of c-myc.

MATERIAL

Archival paraffin wax embedded tissues of cervical squamous cell carcinomas, stage I and II, retrieved from the files of the department of pathology, University College Cork, Ireland: 40 cases were examined for alterations in exon 1 of c-myc; 57 cases were used for immunocytochemical p62 analysis.

METHODS

c-myc exon 1 PCR on HPV positive and negative stage I and II cervical squamous cell carcinomas was performed using primers designed to fragile sites in exon 1 of the c-myc oncogene, which are frequently involved in translocation phenomena and deletions in other neoplasms. This region is bordered by two promoter sequences P1 and P2. In addition, the expression of p62 was evaluated using the monoclonal antibody Mycl-9E10.

RESULTS

Alterations in exon 1 of c-myc were shown in 7.5% of squamous cell carcinomas of the cervix. Changes in exon 1 and 2 of c-myc were also found in COLO 320 cells and Raji cells. These alterations were due to small deletions within exon 1 of c-myc, but point polymorphisms occurring within the priming sites (in one case) may also have occurred. The alterations uncovered appeared "clonal," as replicate samples showed the same amplicon band pattern. Expression of c-myc was variable, with cytoplasmic staining patterns predominating. All cases which showed exon 1 alterations were HPV positive and had strong nuclear positivity on p62 immunocytochemistry.

CONCLUSIONS

Alterations in exon 1 of c-myc occur in a minority of cervical cancers and there was increased expression of p62 in a cohort of HPV positive and negative cervical squamous cell carcinomas. Exon 1 alterations may provide an alternative route to c-myc activation in early squamous cell carcinoma.

Genotypic mapping of HPV and assessment of EBV prevalence in endocervical lesions

AIMS

To examine the prevalence of human papillomavirus (HPV) and Epstein-Barr virus (EBV) in low grade glandular intraepithelial lesions of the cervix, adenocarcinoma with high grade glandular intraepithelial lesions combined, and adenocarcinomas; and to perform a genotyping mapping analysis of endocervical carcinomas to determine the extent of HPV infections in such lesions.

MATERIAL

Archival paraffin wax embeded material from the files of the departments of pathology, National Maternity Hospital, Dublin, and University College Cork, Ireland.

METHODS

HPV prevalence was examined using type specific HPV PCR, general primer HPV PCR (pan HPV screen), nonisotopic in situ hybridisation (NISH), and PCR in situ hybridisation (PCR-ISH). In situ hybridisation was performed using fluorescein labelled oligonucleotide cocktail for eber transcripts of EBV. Genotypic analysis was performed, in all cases where possible, using a grid system.

RESULTS

HPV 16 and 18 were predominantly identified in low grade glandular intraepithelial lesions, high grade glandular intraepithelial lesions, and adenocarcinomas, with HPV prevalence increasing with grade of dysplasia. EBV was only identified in subepithelial lymphocytes in a minority of cases. No link could be shown between HPV and EBV in endocervical lesions. HPV infection was not clonal in endocervical cancer and coexistent adjacent cervical intraepithelial neoplasia, where present, tended to show a similar HPV type.

CONCLUSIONS

The restriction of HPV types 16 and 18 to endocervical lesions suggests that their effect is restricted and specific to endocervical mucosa, but the mechanism of interaction is currently unknown.

PCR in situ hybridisation detection of HPV 16 in fixed CaSki and fixed SiHa cell lines

AIMS

To investigate the feasibility of using fixed cells with the polymerase chain reaction (PCR) in situ hybridisation and to investigate possible reasons for reaction failure.

METHODS

Fixed SiHa and CaSki cells were used in an experimental model of PCR in situ hybridisation for the detection of low and intermediate copy number viral infection in fixed cells.

RESULTS

PCR in situ hybridisation was able to detect one to two copies of human papillomavirus (HPV) 16 in SiHa cells, using small fragment amplicons (120 base pairs), confirming the high detection sensitivity and flexibility of the technique. Problems were encountered with localisation of PCR amplified product in CaSki cells (200-300 copies of HPV 16 per cell) owing to diffusion of product post amplification. Overall, 40% of reactions were successful, which confirms the current unreliability of the technique. Within cell preparations, about 50% of cells contained amplified product.

CONCLUSION

PCR in situ hybridisation represents the marriage of two revolutionary molecular pathological techniques. However, it is currently unreliable, with reaction failure common. Standardised, dedicated equipment is urgently required if the technique is to achieve universal acceptance. In the future, the technique may be used to detect chromosomal translocations in human tumours and to study cellular gene expression.

The importance of fixation procedures on DNA template and its suitability for solution-phase polymerase chain reaction and PCR in situ hybridization

Conventional solution-phase polymerase chain reaction (PCR) and in situ PCR/PCR in situ hybridization are powerful tools for retrospective analysis of fixed paraffin wax-embedded material. Amplification failure using these techniques is now encountered in some centres using archival fixed tissues. Such 'failures' may not only be due to absent target DNA sequences in the tissues, but may be a direct effect of the type of fixative, fixation time and/or fixation temperature used. The type of nucleic acid extraction procedure applied will also influence amplification results. This is particularly true with in situ PCR/PCR in situ hybridization. To examine these effects in solution-phase PCR, beta-globin gene was amplified in 100 mg pieces of tonsillar tissue fixed in Formal saline, 10% formalin, neutral buffered formaldehyde, Carnoy's Bouin's, buffered formaldehyde sublimate, Zenker's, Helly's and glutaraldehyde at 0 to 4 degrees C, room temperature and 37 degrees C fixation temperatures and for fixation periods of 6, 24, 48 and 72 hours and 1 week. DNA extraction procedures used were simple boiling and 5 days' proteinase K digestion at 37 degrees C. Amplified product was visible primarily yet variably from tissue fixed in neutral buffered formaldehyde and Carnoy's, whereas fixation in mercuric chloride-based fixatives produced consistently negative results. Room temperature and 37 degrees C fixation temperature appeared most conducive to yielding amplifiable DNA template. Fixation times of 24 and 48 hours in neutral buffered formaldehyde and Carnoy's again favoured amplification.(ABSTRACT TRUNCATED AT 250 WORDS)

Epstein-Barr virus in normal, pre-malignant, and malignant lesions of the uterine cervix

AIM--To detect the presence or absence of Epstein-Barr virus (EBV) in cervical lesions ranging from normality to invasive malignancy. METHODS--Eighteen randomly selected cases of invasive squamous cell carcinomas of the uterine cervix were examined as well as 25 cases each of normal cervices and those showing cervical intra-epithelial neoplasia (CIN) I, II, and III. DNA-DNA in situ hybridisation, using a biotinylated probe to the Bam H1 "W" fragment of EBV, was carried out in addition to the polymerase chain reaction using specific primer sequences that flank a 153 base pair segment of the Bam H1 "W" region of the EBV genome and which do not cross-amplify other DNA herpes viruses. Positive control material included paraffin wax embedded P3 HR1 lymphoblastoid cells (containing high copy numbers of EBV) and two nasopharyngeal carcinomas positive for EBV. RESULTS--Neither normal nor CIN I tissue was positive. Eight per cent of CIN II tissue was positive; 8% of CIN III, and 43% of carcinomas were positive for EBV. CONCLUSION--The study shows that the virus is present in some cases of cervical carcinoma and to a lesser degree in some premalignant lesions of the cervix, but the exact association between it and cervical oncogenesis, be it causative or incidental, remains to be determined.