Evidence for quiescent S- and G2-phase cells in human colorectal carcinomas: a flow cytometric study with the Ki-67 antibody

The associations among quantitative spectral CT parameters, Ki-67 expression levels and EGFR mutation status in NSCLC

Dual-energy spectral computed tomography (DESCT) is based on fast switching between high and low voltages from view to view to obtain dual-energy imaging data, and it can generate monochromatic image sets, iodine-based material decomposition images and spectral CT curves. Quantitative spectral CT parameters may be valuable for reflecting Ki-67 expression and EGFR mutation status in non-small-cell lung cancer (NSCLC). We investigated the associations among the quantitative parameters generated in DESCT and Ki-67 expression and EGFR mutation in NSCLC. We studied sixty-five NSCLC patients with preoperative DESCT scans, and their specimens underwent Ki-67 and EGFR evaluations. Statistical analyses were performed to identify the spectral CT parameters for the diagnosis of Ki-67 expression and EGFR mutation status. We found that tumour grade and the slope of the spectral CT curve in the venous phase were the independent factors influencing the Ki-67 expression level, and the area under the curve (AUC) of the slope of the spectral CT curve in the venous phase in the receiver operating characteristic analysis for distinguishing different Ki-67 expression levels was 0.901. Smoking status and the normalized iodine concentration in the venous phase were independent factors influencing EGFR mutation, and the AUC of the two-factor combination for predicting the presence of EGFR mutation was 0.807. These results show that spectral CT parameters may be useful for predicting Ki-67 expression and the presence of EGFR mutation in NSCLC.

Correlations between the iodine concentrations from dual energy computed tomography and molecular markers Ki-67 and HIF-1α in rectal cancer: A preliminary study

PURPOSE

To investigate whether dual energy computed tomography (CT) with iodine quantification is correlated with molecular markers Ki-67and hypoxia-inducible factor 1α (HIF-1α)in rectal cancer (RC).

MATERIALS AND METHODS

Eighty patients (43 males and 37 females) diagnosed with rectal cancer got pelvic contrast-enhanced CT scan with dual energy computed tomography before any anticancer treatment. Analyse the normalized iodine concentration (NIC) values and CT values at each energy level (40-140 keV) from the virtual monochromatic image of the primary lesions. The postoperative specimens of all 80 patients underwent Ki-67 and HIF-1α immunohistochemistry staining. By SPSS17.0 software package, we analyzed the correlations of NIC values and CT values at each energy level (40-140 keV) with Ki-67 and HIF-1α expression. The receiver operating characteristic (ROC) curves of these dual energy computed tomography parameters were calculated and the diagnostic value were assessed.

RESULTS

There was a weak positive correlation between NIC values and carcinoembryonic antigen level (r=0.246, P=0.028) in RC. Both the value and the level of Ki-67 expression were correlated positively with the NIC values (r=0.344, P=0.002 and r=0.248, P=0.026). HIF-1α expression was correlated positively with the NIC values of the RC (r=0.598, P<0.001). The best threshold values of NIC values in diagnosing the expression of HIF-1α was 0.5839. The sensitivity, 78%; specificity, 87%; PPV, 86%; NPV,79%;accuracy, 83%.

CONCLUSION

The NIC values on dual energy computed tomography may be used as a measurement of hypoxia in RC and determining the ability of tumor invasion noninvasively.

Management of colorectal cancer patients after resection of liver metastases: can we offer a tailored treatment?

Surgical resection remains the only option of cure for patients with colorectal liver metastases, and no patient should be precluded from surgery. There is much controversy not only regarding the most appropriate therapeutic approach in the neoadjuvant setting but also after surgery is performed. Many patients will experience early relapses but others will be long survivors. We need to establish reliable prognostic and predictive factors to offer a tailored treatment. Several prognostic factors after metastasectomy have been identified: high C-reactive protein levels, a high neutrophil-lymphocyte ratio, elevated neutrophil count and low serum albumin are related to a worst outcome. Elevated CEA and Ki 67 levels, intrahepatic and perihepatic lymph node invasion are also some of the markers related to a worst outcome. In contrast, the administration of preoperative chemotherapy has been associated with a better prognosis after hepatectomy. The administration of adjuvant chemotherapy should be done taking in consideration these factors. Regarding predictive factors, determination of ERCC1, TS, TP and DPD and UGT1 polymorphisms assessment could be considered prior to chemotherapy administration. This would avoid treatment related toxicities and increase this population quality of life.

Chromatin-bound PCNA as S-phase marker in mononuclear blood cells of patients with acute lymphoblastic leukaemia or multiple myeloma

OBJECTIVES

Proliferating cell nuclear antigen (PCNA) has often been used as a marker to aid assessment of tumour growth fraction. This paper addresses the question of whether it can be used as an S-phase marker, when the non-chromatin-bound form of the protein is removed by pepsin treatment.

MATERIALS AND METHODS

Cytofluorometric measurements were carried out after immunofluorescence staining of PCNA and counterstaining of DNA. S-phase fraction was determined with the help of windows on PCNA versus DNA scattergrams, or mathematically from DNA histograms.

RESULTS

S-phase fractions obtained using the two methods correlated well, but did not always agree, exact discrepancies depending on the mathematical model used for histogram analysis.

CONCLUSIONS

Determination of S-phase fractions with the help of PCNA immunofluorescence staining is possible, and probably more reliable than calculation of S-fractions from DNA histograms. It thus offers an alternative to assays involving BrdU labelling in vivo.

Increased radiosensitivity with chronic hypoxia in four human tumor cell lines

PURPOSE

It is well known that the radiosensitivity of tumor cells can be significantly reduced under hypoxic conditions. However, most of the reports in the literature refer to an experimental setup in which the supply of oxygen is kept low for a short period of time only. In tumors, chronic hypoxia would seem to be the more typical situation, because of an insufficient vascularization and the limited diffusion of oxygen into the tissue. Under such conditions, certain changes in the proliferation patterns of tumor cells, in which the cell cycle checkpoint protein p53 seems to play a role, have been shown to occur. We therefore decided to study radiosensitivity and cell cycle progression under conditions of chronic hypoxia in several human tumor cell lines differing in their p53 status.

METHODS AND MATERIALS

Four human tumor cell lines (melanomas Be11 and MeWo and squamous carcinomas 4197 and 4451) were incubated for 3 h, 24 h, and 72 h under either oxic or hypoxic conditions and subsequently exposed to graded doses of X-rays. In some cases, cells were kept under hypoxia for the same periods of time, but then reoxygenated immediately before irradiation. Cell survival was assessed with the usual colony formation assay, and cell cycle distributions were determined by two-parameter flow cytometry after labeling with bromodeoxyuridine (BrdU).

RESULTS

As expected, the oxygen enhancement ratio at 3 h was 2.0 or more in all cases. Differences, however, became evident with longer incubation times. At 24 h, the sensitivity of cells kept under hypoxic conditions both before and during irradiation was practically unchanged with cell lines Be11, 4197, and 4451, but clearly increased with MeWo. This resulted in an oxygen enhancement ratio of only 1.1 for the latter cell line when the sensitivity of aerated cells was used as reference. Cells kept under hypoxia for 24 h and reoxygenated shortly before irradiation, however, also showed an increase in sensitivity, so that the oxygen enhancement ratio based on differences in irradiation atmosphere alone was still around 2.0. At 72 h, the two p53 wild-type cell lines were not available for experiments, because they quickly degenerated under hypoxic conditions. Both mutant cell lines now showed similar results, the sensitivity being increased with irradiation under continued hypoxia as well as after reoxygenation. The oxygen enhancement ratios with reference to aerated cells were 1.3 and 1.5 for MeWo and 4451, respectively. Flow cytometric measurements after labeling with BrdU revealed that in all cell lines, the fraction of active S-phase cells during incubation tended to decrease under hypoxic conditions. Only in the p53 mutant cell lines, however, was this accompanied by an increase of the percentage of S-phase cells that were not actively incorporating BrdU.

CONCLUSIONS

It is suggested that these quiescent cells in the S-phase compartment develop because of a general breakdown of cellular energy metabolism. In the p53 mutant cells, this may lead to a cessation of cell cycle progression in all phases alike, because checkpoint control has been lost; p53 wild-type cells, on the other hand, settle down preferentially in G(1) under the same conditions. Independently of the p53 status, however, energy depletion may be the cause of a decreased ability to cope with radiation damage and thus the cause of the observed increase in radiosensitivity. This would become more easily apparent in the p53 mutant cell lines, because they are less sensitive than the p53 wild types to hypoxia as such.

Cell proliferation in colorectal adenocarcinomas: comparison between Ki-67 immunostaining and bromodeoxyuridine uptake detected by immunohistochemistry and flow cytometry

We compared three different means of assaying tumor proliferative activity in 30 human colorectal adenocarcinomas labeled in vivo with bromodeoxyuridine (BrdUrd). The labeling indices (LI) of BrdUrd obtained both by flow cytometry (FCM) and immunohistochemistry (IH) were also compared with the labeling index of Ki-67. These methods were then related to tumor ploidy and pathological features. Flow cytometry was performed in accordance with Begg's method after intravenous infusion of BrdUrd four hours before surgery. Immunohistology was carried out on paraffin-embedded sections with monoclonal antibodies against BrdUrd and Ki-67. A positive correlation was found between BrdUrd LI obtained by both FMC and IH (p<0.0001), a finding that complies with the literature. However, we report on a correlation between Ki-67 LI and BrdUrd LIs in colorectal tumors (p=0.012). The results were valid for all tumors when they were subdivided into diploid and aneuploid groups. The labeling indices were significantly higher in the aneuploid tumor group than in the diploid group (p=0.047). No relationship between proliferation parameters and tumor stage or grade was found. To our knowledge, this is the first report on a positive correlation between tumor proliferation indices in BrdUrd LIs and Ki-67 in colorectal carcinomas. This finding validates the value of Ki-67 immunostaining, which, however, should be confirmed in a larger series under the same technical conditions.

Proliferation kinetics and prognosis in gastric cancer after resection

The influence of proliferation and proliferation kinetics on prognosis in gastric cancer after complete resection are controversial. In a prospective study we investigated the tumour specimens of 111 patients after resection of gastric cancer, who received 200 mg intravenous (i.v.) bromodeoxyuridine (BrdU) pre-operatively. The following biological parameters were analysed in the tumour tissue using flow-cytometry: DNA ploidy, proportion of S-phase cells, BrdU labelling index (LI), DNA synthesis time (T(s)), potential tumour doubling time (T(pot)), proliferating cell nuclear antigen (PCNA) and Ki-67 LI. The median follow-up time was 40 months (range 19-62 months). Besides the established pathohistological prognostic factors, univariate analysis revealed a prognostic influence on survival for BrdU LI, T(pot) and the proportion of S-phase cells. By multivariate Cox analysis of the completely resected cases, only tumour stage and T(pot) had a significant, independent influence on survival. By classification and regression trees (CART) analysis, resection status, tumour stage and T(pot) defined risk groups with significantly different outcomes. A short T(pot) was a predictor of better survival in stage I, II and IIIA tumours. Ploidy and the other investigated proliferation-related parameters failed to demonstrate any influence on prognosis after resection of gastric cancer.

Relevance of Ki-67 antigen expression and K-ras mutation in colorectal liver metastases

AIMS

The liver is a frequent site of metastases from colorectal cancer. While these lesions are potentially amenable to surgical resection, they are usually very aggressive, and recurrence is frequent. Mutations of the proto-oncogene K- ras are thought to impart a strong growth signal to tumour cells and are closely associated with the development of malignancies of the colon and rectum. Hepatic metastases from colorectal cancer have notably elevated proliferative rates. The present study was performed to investigate the relationship between proliferation or K- ras mutation and prognosis following curative resection of colorectal liver metastases.

METHODS

Colorectal liver metastases from 41 patients undergoing curative hepatic resection were examined for proliferation status and presence of K- ras mutations. The proliferative activity was assessed by Ki-67 immunohistochemistry. DNA from the same tissue samples was screened for point mutations in codon 12 of the K- ras gene using a novel microplate-based allelic-specific hybridization assay. Ki-67 scores and K- ras status were then related with patient survival as determined through retrospective analysis.

RESULTS

Median survival was 40 months. Patients with high Ki-67 scores (> or = 50%) had significantly shorter median survival compared with those with low scores (30 vs 44 months, log-rank P=0.02). A high Ki-67 score was an independent negative prognostic factor by multivariate regression analysis (relative risk=3.04, P=0.036). K- ras point mutations were detected in 6/41 patients (15%), but mutational status did not correlate with Ki-67 score or survival.

CONCLUSIONS

These findings suggest that the tumour proliferative index is a useful predictor of aggressive tumour behaviour and an indicator of patient survival. The presence of K- ras mutations does not appear to correlate with tumour proliferation status or patient survival.

The prognostic value of proliferation indices: a study with in vivo bromodeoxyuridine and Ki-67

Proliferation indices are intended to help patients and clinicians make treatment decisions. We have previously demonstrated that a proliferation index based on in vivo labeling of S-phase cells with bromodeoxyuridine (BrdUrd) correlates with Ki-67 labeling index (LI). We now compare the prognostic value of these indices. With written consent, we gave 129 women with biopsy confirmed breast cancer 200 mg/M2 BrdUrd during 30 min immediately preceding surgery. We used IU-4 anti BrdUrd antibody to count the immunohistochemical labeling index (LI) of DNA-incorporated BrdUrd in 2,000 cells and MIB-1 to count Ki-67 (118 cases). Patients received standard surgical and adjuvant treatment. No patients were lost to follow-up and patients were followed a minimum of 2 (median 5.1) years. We compared survival and recurrence in tumors with high vs low labeling indices. We found that women in the low BrdUrd LI group had better disease free survival (92% vs 67% 5-yr DFS p = 0.001) and overall survival (94% vs 70% 5-yr OS, p = 0.0001) than those with a high LI. In comparison, a low Ki-67 index predicted better OS (87% vs 80% 5-yr OS, p = 0.020) and a trend for better DFS (84% vs 72% DFS p = 0.055). The apparent superiority of BrdUrd LI over Ki-67 LI is likely due to chance (p = 0.18). In multivariate survival analyses we found that BrdUrd LI proliferative index significantly improves prediction of DFS or OS even when node status, age or tumor size is in the model. We conclude that markers of proliferation are useful adjuncts in predicting patient prognosis.

Quiescent S-phase cells as indicators of extreme physiological conditions in human tumor xenografts

PURPOSE

During the last 20 years, evidence has been accumulating for the existence in animal and human tumors of quiescent S-phase cells, i.e. cells with an S-phase DNA content that do not actively synthesize DNA. In cell culture studies, quiescent S-phase cells have been observed under physiological conditions typical for poorly vascularized regions of tumors such as reduced pH, hypoxia, and glucose deprivation. Therefore, we studied the possible correlation between the frequency of quiescent S-phase cells and the oxygenation status as determined polarographically in a number of human tumor xenografts.

METHODS AND MATERIALS

Five human tumor xenografts on nude mice were used. Oxygenation was measured polarographically with an Eppendorf pO2-Histograph in 24 to 30 individual tumors for each entity. Mice were injected intraperitoneally with 1 mg/30 g bodyweight bromodeoxyuridine (BrdU), tumors were excised 30 min later and prepared into a single-cell suspension. After immunofluorescence staining with an antibody against BrdU and staining of the DNA with propidium iodide, cells were measured in a FACScan flow cytometer and the frequency of cells in the S-phase compartment that did not incorporate BrdU was determined.

RESULTS

In most cases, the frequency of measurements of an oxygen partial pressure <5 mm Hg in the tumor tissue increased with tumor volume. Likewise, the frequency of quiescent S-phase cells was generally higher in larger tumors. Taking all five tumor entities together, there was a highly significant correlation between tumor oxygenation and the occurrence of quiescent S-phase cells.

CONCLUSIONS

Our data confirm earlier findings that inactive S-phase cells do exist in vivo. Because their frequency seems to be dependent (directly or indirectly) on the degree of oxygenation and has been shown to increase not only with hypoxia, but also with reduced pH and glucose deprivation in vitro, the frequency of inactive S-phase cells may be considered a summary indicator for extreme physiological conditions in tumors.

The functional relationship between in vivo bromodeoxyuridine labeling index and Ki-67 proliferation index in human breast cancer

Proliferation indices are used, along with other parameters, to estimate the risk of recurrence of breast cancer for individual patients. Because it is unlikely one index will be practical for all patients, it is important to understand the relationship between various indices of proliferation. For this reason, we compared a proliferation index based on in vivo labeling of S-phase tumor cells with the thymidine analog bromodeoxyuridine (BrdUrd), to a proliferation index based on an estimate of the growth fraction with the MIB-1 antibody to the Ki-67 antigen. With informed consent, we gave 145 patients 200 mg/m2 BrdUrd intravenously just prior to surgical removal of breast cancer. On histology sections, we visually counted S-phase cells which had incorporated BrdUrd using the Br-3 antibody which is specific to DNA-incorporated BrdUrd, and we counted cells in the growth fraction using the MIB-1 antibody to the Ki-67 antigen. We found that both indices were positively correlated with tumor size, number of positive nodes, and tumor grade, and both were negatively correlated with age and estrogen-progesterone receptor positivity. Using a linear functional relationship model, we found that the best (i.e. the maximal) fit between the two indices (correlation coefficient 0.79; p < 0.0001) occurred when each index was square root transformed, as is appropriate when counts follow a Poisson distribution. When we used the median as a cutpoint for each index, the classification of 19 percent of data pairs changed depending upon which index was used. We also estimated that the Ki-67 intercept (1.02 +/- 0.25) was significantly greater than zero. We conclude that the BrdUrd index of DNA synthesis in S-phase correlates highly with the MIB-1 index of the growth fraction, and both indices correlate well with other parameters of tumor aggressiveness. Because this correlation is driven by concordance of the extremes of high and low counts, clinical comparison will be necessary to determine which is the better prognostic marker for human breast cancer.