Measurement of proliferation activities in human tumor models: a comparison of flow cytometric methods

Comparative Proliferation Capacity of Gag-C-Specific Naive and Memory CD4+ and CD8+ T Lymphocytes in Rapid, Viremic Slow, and Slow Progressors During Human Immunodeficiency Virus Infection

The exact cause of altered dynamics in T cells compartment during HIV infection remains elusive to date. In this longitudinal study, the proliferation frequency of different T cell subsets was investigated in untreated HIV-1-infected Indian individuals stratified as rapid (R), viremic slow (VS), slow (S) progressors, and healthy controls. Ten healthy and 20 treatment-naive HIV-1-infected individuals were enrolled. Expression of Ki67 nuclear antigen was examined on HIV-specific T cell subsets in peripheral blood lymphocytes. Upon stimulation with HIV-1 Gag-C peptide pools, effector memory (EM) CD4 T cells (R vs. S, EM CD4, p < 0.05) of R progressors proliferated significantly compared with those of S progressors at baseline. However, central memory (CM) CD8 T cell subsets proliferated significantly in VS and S progressors compared with those in R progressors, wherein highest proliferation frequency of EM CD8 T cells was observed. At follow-up visit, the proliferation frequency of naive CD8 T cells was significantly higher in R progressors than S progressors (R vs. S naive CD8, p < 0.05). The findings suggest altered dynamics of different CD4+ and CD8+ T cell subsets in R, VS, and S progressors. The increase in CM T cell proliferation in VS and S progressors could be attributed to slower progression of the HIV infection. Hence, treatment strategies must be focused on restoring the homeostatic balance to restore T cell functionality.

Novel Strategies for Breast Cancer Imaging: New Imaging Agents to Guide Treatment

The development of molecular therapies for cancer treatment has created a need to image biochemical and molecular processes to appropriately select tumors that express the drug target, thereby predicting a positive response to therapy. Biomarker-driven molecular imaging is complementary to pathologic analysis and offers a more direct measure of drug efficacy and treatment response, potentially providing early insight into therapeutic futility and allowing response-adapted treatment strategies. Imaging also allows a unique means of assessing the heterogeneity of both intra- and intertumoral targets as well as a mixed response to therapy; this information is important in the setting of metastatic disease. Here we review the development of novel molecular imaging probes and combinations of probes to guide therapy for two new targets and associated therapeutic agents: cyclin-dependent kinase inhibitors and poly(adenosine diphosphate-ribose) polymerase inhibitors.

PET Radiotracers for Imaging the Proliferative Status of Solid Tumors

Two different strategies have been developed for imaging the proliferative status of solid tumors with the functional imaging technique, Positron Emission Tomography (PET). The first strategy uses carbon-11 labeled thymidine and/or, more recently, fluorine-18 labeled thymidine analogs. These agents are a substrate for the enzyme thymidine kinase-1 (TK-1) and provide a pulse label of the number of cells in S phase. The second method for imaging the proliferative status of a tumor uses radiolabeled ligands that bind to the sigma-2 receptor which has a 10-fold higher density in proliferating (P) tumor cells versus quiescent (Q) tumor cells. This article compares and contrasts the two different strategies for imaging the proliferative status of solid tumors, and describes the strengths and weaknesses of each approach.

Diagnostic utility of cell cycle and apoptosis regulatory proteins in verrucous squamous carcinoma

A major problem in the diagnosis of verrucous squamous cell carcinoma is the lack of readily reproducible objective criteria for distinguishing this malignant lesion from reactive epithelial hyperplasia. Both lesions are characterized by thickened (well-differentiated) squamous epithelium without cellular atypia and subjacent stroma densely infiltrated by lymphocytes and plasma cells. This study was carried out to evaluate the use of cell cycle and apoptosis-related regulatory proteins in the diagnosis of verrucous carcinoma. The study materials consisted of representative formalin-fixed and paraffin-embedded tissue blocks from 19 cases of verrucous carcinoma, 18 classic squamous cell carcinoma, and 14 squamous epithelial hyperplasia (acanthosis). The immunohistochemical expression of the following of cell cycle and apoptosis-related regulatory proteins was evaluated using avidin-biotin complex detection technique: p16, p21, p53, Ki67, and retinoblastoma gene product (RBGP) (also known as retinoblastoma protein [pRb]). Expression of Ki67 was detected only in the single basal layer of the epithelium in all 14 cases of acanthosis. In verrucous carcinoma, Ki67 was detected in basal and suprabasal cells in the lower third of the neoplastic epithelium in 19 of 19 cases (100%). In neoplastic squamous epithelium with frankly invasive squamous cell carcinoma, Ki67 was diffusely expressed throughout the entire thickness of the epithelium as well as in the underlying invasive tumor nests. The pattern of p53 expression was similar to that of Ki67 in all the experimental groups, with a Pearson correlation coefficient of 0.98. In addition, immunohistochemical expression of p53 in the hyperplastic squamous epithelium was very weak, in contrast to the more intense immunoreactivity observed in verrucous carcinoma and classic squamous cell carcinoma. There was an overlapping in the expression of p16, p21, and RGBP in all the experimental groups, being present in more than half the thickness of the epithelium in 50% to 100% cases in each study group. We therefore conclude that the pattern of Ki67 and p53 expression in verrucous carcinoma is readily reproducible and distinctly different from that observed in epithelial hyperplasia and that seen in invasive squamous cell carcinoma. Thus Ki67, and p53 immunostains are reliable adjuncts that may be helpful in resolving diagnostic problems associated with verrucous carcinoma.

Estimating cell death in G2M using bivariate BrdUrd/DNA flow cytometry

BACKGROUND

In an accompanying paper (Asmuth et al.) it was found necessary to include cell death explicitly to estimate parameters of cell proliferation. The use of bivariate flow cytometry to estimate the phase durations and the doubling times of cells labeled with thymidine analogues is well established. However, these methods of analysis do not consider the possibility of cell death. This report demonstrates that estimating cell death in G(2)/M is possible.

METHODS

Mathematical models for the experimental quantities, the fraction of labeled undivided cells, the fraction of labeled divided cells, and the relative movement were developed. These models include the possibility that, of the cells with G(2)/M DNA content, only a certain fraction will divide, with the remainder dying after some time T(R). Simulation studies were conducted to test the possibility of using simple methods to estimate phase durations and cell death rates.

RESULTS

Cell death alters the estimates of phase transit times in a rather complex manner that depends on the lifetime of the doomed cells. However, it is still possible to obtain estimates of the phase durations of cells in S and G(2)/M and the death rates of cells in G(2)/M.

CONCLUSIONS

The methods presented herein provide a new way to characterize cell populations that includes cell death rates and common measurements of cell proliferation.

Detection of serine 473 phosphorylated Akt in acute myeloid leukaemia blasts by flow cytometry

The phosphoinositide 3-kinase/Akt signalling pathway is a recently recognized important parameter in the prognosis and the response to treatment of acute myeloid leukaemia (AML). Akt kinase is activated by phosphorylation on Thr 308 and Ser 473. Active Akt promotes cell growth and survival to apoptotic insults. Thus, it seems important to evaluate Akt phosphorylation in AML blasts. This work aimed to establish whether it was possible to detect Akt phosphorylation on Ser 473 of AML blasts by means of flow cytometry. High levels of Akt activity and phosphorylation were detected in 13 of 15 cases of AML. Flow cytometric analysis revealed similar patterns of Ser 473 expression as was observed with Akt kinase activity and Western blot analysis of Thr 308 and Ser 473 phosphorylation. Double immunostaining enabled the simultaneous flow cytometric detection of an AML-associated antigen (CD33) and Ser 473 phosphorylated Akt in leukaemic blast populations. Our results indicate that flow cytometry enabled the rapid and quantitative assessment of Ser 473 phosphorylated Akt of AML blasts that, when used in combination with cell surface staining, can provide more accurate phenotyping of AML blasts.

A prospective study of pre-treatment cell kinetics and clinical outcome in nasopharyngeal carcinoma

BACKGROUND AND PURPOSE

To study pre-treatment cell kinetics and their clinical correlations in nasopharyngeal carcinoma (NPC).

MATERIALS AND METHODS

Ninety newly diagnosed NPC patients were studied using in vivo Bromodeoxyuridine (BrdU) labeling and flow cytometric analysis. Immunohistochemical staining for BrdU and Ki 67 was also performed.

RESULTS

The median S-phase duration (Ts) was 6.2 h (range 3.5-18.7 h), median flow cytometric labeling index (FCM-LI) was 7.4% (1.3-37.6%), and median potential doubling time (Tpot) was 3.6 days (0.5-19.9 days). The median histologic labeling index (H-LI) was 12.4% (1.2-43.3%), and median histologic Tpot (H-Tpot) was 2.1 days (0.5-33.3 days). FCM-LI and H-LI were both positively correlated with Ki67 whereas Tpot and H-Tpot were both negatively correlated with Ki67 and N-stage. In univariate analysis, Tpot and H-Tpot showed a trend for progression free survival. Tpot was significantly associated with local relapse free survival, but lost its significance in multivariate analysis. N-stage was the only significant prognostic factor for all radiotherapy outcomes in both univariate and multivariate analyses.

CONCLUSIONS

Tpot was the only pre-treatment cell kinetic parameter for which some evidence was found for an association with survival in NPC patients. Future studies should aim to combine cell kinetic parameters together with other biological markers and clinical parameters to provide more useful prognostic information to guide individual patient's therapy.

Bombesin-like peptides and mast cell responses: relevance to bronchopulmonary dysplasia?

Bombesin-like peptides (BLPs) are elevated in newborns who later develop bronchopulmonary dysplasia (BPD). In baboon models, anti-BLP blocking antibodies abrogate BPD. We now demonstrate hyperplasia of both neuroendocrine cells and mast cells in lungs of baboons with BPD, compared with non-BPD controls or BLP antibody-treated BPD baboons. To determine whether BLPs are proinflammatory, bombesin was administered intratracheally to mice. Forty-eight hours later, we observed increased numbers of lung mast cells. We analyzed murine mast cells for BLP receptor gene expression, and identified mRNAs encoding bombesin receptor subtype 3 and neuromedin-B receptor (NMB-R), but not gastrin-releasing peptide receptor. Only NMB-R-null mice accumulated fewer lung mast cells after bombesin treatment. Bombesin, gastrin-releasing peptide, NMB, and a bombesin receptor subtype 3-specific ligand induced mast cell proliferation and chemotaxis in vitro. These observations support a role for multiple BLPs in promoting mast cell responses, suggesting a mechanistic link between BLPs and chronic inflammatory lung diseases.

Flow cytometric detection of total and serine 473 phosphorylated Akt

The evaluation of regulatory proteins is important for biological studies and is also established as a prognostic marker for cancer diagnosis. Very recently, it has been highlighted that the serine/threonine kinase Akt plays a fundamental role in survival pathways and is also involved in the onset of resistance to anti-neoplastic drugs and ionizing radiation in cell lines derived from solid tumors. For its full activation Akt needs to be phosphorylated on Serine 473 residue. Molecules that are fundamental in determining resistance to therapeutic treatments might serve in the future as clinical markers to tailor therapy and/or predict treatment response. The aim of this study was to ascertain whether or not flow cytometric analysis of total Akt and of its form phosphorylated on Serine 473 could be related to standard techniques such as Western blotting with phosphospecific antibodies and in vitro kinase assay. To this end, we employed as experimental models HL-60 and PC-12 lines in which there is an enhancement of Akt activity. Our results showed that flow cytometry analysis, performed on fixed and permeabilized cells, correlated well with the results provided by in vitro activity assays and Western blots. Therefore, our findings might indicate that flow cytometric study of Akt (both total and phosphorylated) content may be applied in routine work for phenotyping of hematological and non-hematological neoplasias, and allow for its use as a useful marker for the classification and the prognosis of neoplastic diseases.

Impact of neoadjuvant chemotherapy on Ki-67 and PCNA labeling indices for esophageal squamous cell carcinomas

PURPOSE

The effects of neoadjuvant chemotherapy (CT) on Ki-67 and proliferating cell nuclear antigen (PCNA) labeling index (LI) were analyzed, using biopsy and surgical specimens of esophageal cancer.

METHOD AND MATERIALS

Immunohistochemical staining for Ki-67 and PCNA was performed for biopsy and surgical specimens of 35 patients with esophageal squamous cell carcinoma. Seventeen patients were treated with neoadjuvant CT (CT group), while no preoperative treatment was performed for the remaining 18 patients (control group). As neoadjuvant CT, cisplatin of 50 mg/body/week was administered 2-5 times (100-250 mg in total) until 7-10 days before subtotal esophagectomy.

RESULT

Significant correlation between the LIs of biopsy and surgical specimens was observed for the control group (p = 0.006 for Ki-67 and p = 0.005 for PCNA), although both LIs of surgical specimens were significantly higher than those of biopsy specimens (p < 0.05). However, no significant correlation between LIs of biopsy specimens and those of surgical specimens was observed for the CT group. In addition, the LIs of the surgical specimens of the CT group were significantly lower than the LIs of the control group (p < 0.005 for Ki-67 and p < 0.05 for PCNA). Significant decrease in Ki-67 LI after neoadjuvant CT was noted especially for well or moderately differentiated squamous cell carcinomas and/or tumors treated with high-dose cisplatin (150-250 mg).

CONCLUSION

Significant correlation of Ki-67 and PCNA LIs between biopsy and surgical specimens was demonstrated for the control group. Neoadjuvant CT decreased the percentage of cycling and proliferative tumor cells of esophageal cancer.

Evaluation of apoptosis as a prognostic factor in myelodysplastic syndromes

The myelodysplastic syndromes (MDS) are a group of disorders characterized by peripheral pancytopenia despite normo- or hypercellular bone marrow. This is thought to be as a result of the apoptosis of haematopoietic bone marrow cells resulting in ineffective haematopoiesis. To clarify the relationship between prognosis and apoptosis and/or cell proliferation in the bone marrow, we studied 51 cases with MDS. Bone marrow biopsies were stained immunohistochemically for MIB-1 (marker for proliferating cells) and CD34 (marker for stem cells). Apoptosis was visualized by detection of DNA fragmentation using TdT incorporation of nucleotides on 3' ends of DNA (TUNEL technique) and expressed as the apoptotic rate. MDS patients included 32 with refractory anaemia (RA), one RA with ringed sideroblasts (RARS) patient, seven RA with excess of blasts (RAEB) patients, eight patients with RAEB in transformation (RAEB-t) and three patients with chronic myelomonocytic leukaemia (CMMoL). In addition, we also studied six cases with acute myeloid leukaemia (AML) arising from MDS (AML-MDS) and ten control subjects. Fatal pancytopenia was the cause of death in 19 out of 51 patients. The apoptotic rate was higher in MDS patients (5.5%) than in control subjects (0.6%) and AML-MDS patients (0.4%). The percentage of MIB-1 positive cells was higher in MDS and AML-MDS than in control. The percentage of CD34-positive cells was higher in AML-MDS, RAEB, RAEB-t and CMMoL patients than control subjects and RA patients. Our findings indicate the activation of both the proliferative and apoptotic rates in MDS. Poor prognosis correlated significantly with higher apoptotic rates, but not with percentages of MIB-1 and CD34-positive cells. Our results suggest that apoptosis might be a useful prognostic factor and inhibition of apoptotic mechanisms may induce leukaemic transformation in MDS.