Endothelial cell dysfunction and cytoskeletal changes associated with repression of p16(INK4a) during immortalization

The immortalization process is a fundamental step in the development of most (if not all) human cancers, including the aggressive endothelial cell (EC)-derived malignancy angiosarcoma. Inactivation of the tumor suppressor p16^INK4a and the development of multiple chromosomal abnormalities are features of angiosarcoma that are recapitulated during telomerase-mediated immortalization of human ECs in vitro. The present study used a panel of telomerase-immortalized bone marrow EC (BMEC) lines to define the consequences of inactivation of p16^INK4a on EC function and to identify molecular changes associated with repression of p16^INK4a. In a comparison of two immortalized BMEC mass cultures and six clones, the cell lines that repressed p16^INK4a showed a higher rate of proliferation and an impaired ability to undergo morphogenic differentiation and form vessel-like structures in vitro. Proteomic comparison of a p16^INK4a-negative and a p16^INK4a-positive BMEC mass culture at early- and late-passage time points following transduction with telomerase reverse transcriptase (hTERT) revealed altered expression of cytoskeletal proteins, including vimentin and α-tropomyosin (αTm), in the immortal cells. Immunoblot analyses of a panel of 11 immortal clones showed that cells that lacked p16^INK4a expression tended to accumulate more dramatic changes in these cytoskeletal proteins than cells that retained p16^INK4a expression. This corresponded with aberrant cytoskeletal architectures among p16^INK4a-negative clones, which featured thicker actin stress fibers and less fluid membrane ruffles than p16^INK4a-positive cells. A direct link between p16^INK4a repression and defective EC function was confirmed by analysis of normal cells transfected with small interfering RNA (siRNA) targeting p16^INK4a. siRNA-mediated repression of p16^INK4a significantly impaired random motility and vessel formation in vitro. This report is the first to demonstrate that ECs that repress the expression of p16^INK4a are prone to defects in motility, morphogenesis and cytoskeletal organization. These defects are likely to reflect alterations that occur during the development of EC-derived malignancies.

P3-01-04: Differential Impact of Gefitinib and PLX4720 on Proliferation of MCF10A and Isogenic Lines as Measured with a Metastasis Expression Score

Background: We previously reported that a published “Metastasis Score” (MS) could be used to evaluate the effects of a PI3K inhibitor (GDC-0941) on mutated human isogenic breast cancer cell lines. MS, based on the expression of14 genes, has been shown to predict distant metastasis in ER(+), node (−), breast cancer. We were interested to determine the impact of gefitinib (EGFR inhibitor) and PLX-4720 (selective inhibitor of BRAF V600E) on MS to assess the applicability of this score to a broader class of targeted agents. In addition, given the cross-talk between metabolism and proliferation, we also profiled genes involved in glycolysis, fatty acid metabolism and oxidative phosphorylation.

Methods: Parental MCF10A (WT for all genes) and isogenic lines of MCF10A harboring PI3K (H1047R), p53 null or KRAS(G12V) mutations were cultured overnight in DMEM:F12 media under identical conditions. Cells were then treated with gefitinib, PLX4720, or DMSO (vehicle control) and further incubated for 24hr. Expression analysis was performed by RT-PCR.

Results: The MS of the PI3K (H1047R) and p53 null lines was higher than the parental line and lower for the KRAS (G12V) line. Treatment of parental, PI3K and KRAS cell lines with gefitinib resulted in dose-dependent decreases in MS, as reported for GDC-0941, with a higher dose required to inhibit growth of PI3K (H1047R) cells. Treatment of p53 null cells with gefitinib, however, had only a modest effect on MS. In contrast to gefitinib, MS increased with PLX-4720 treatment in all 4 lines; the greatest increase was observed in KRAS (G12V) cells. The expression of metabolic genes differed significantly depending on the oncogenic mutation harbored by the cell line. ACTA2, ACLY, RPIA, KHK, GLS2 were most highly expressed in p53 null but lowest in KRAS (G12V), while GLUT5, PFKFB4, ENO3, SLC27A1, PGK2, GLUT1, TKT were expressed most highly in KRAS (G12V) but lowest in PI3K(H1047R). Upon treatment with gefitinib or PLX-4720, genes that were downregulated in the mutated lines generally showed a dose-dependent increase; those that were upregulated relative to the parental, showed a dose-dependent decrease with treatment.

Discussion: The decrease in MS of the parental, PI3K (H1047R) and KRAS (G12V) cell lines treated with gefitinib supports the impact of this EGFR inhibitor on cell proliferation. The modest effect on MS in p53 null cells supports the findings that sensitivity to gefitinib requires active p53 in order to induce apoptosis through a p53-dependent pathway. Increases in MS were observed in all 4 cell lines treated with PLX-4720, with the largest increase observed in KRAS (G12V). The enhanced proliferation of a BRAF WT cell line with a KRAS mutation is consistent with the Ras-dependent nature of this pathway. The metabolic genes showed diverse expression patterns that differed with different oncogenic mutations and likely reflect the multiple mechanisms controlling metabolism in cancer. An improved understanding of the expression of metabolic genes relative to proliferation in cell lines with various oncogenic mutations may provide additional insights into the dysregulation of these cellular processes and the possible role of anti-metabolite intervention.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-01-04.

A study of atherosclerosis in patients after radiation for early breast cancer

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Background: Radiation therapy (RT) is widely used as part of curative treatment of breast cancer. However, older studies have shown increased cardiac morbidity and mortality from breast RT. A screening method is needed to detect early cardiac damage in this population. Recent data have shown that Electron beam computed tomography (EBCT) can detect early atherosclerosis in coronary arteries by identifying the amount of calcification in the coronaries. In our study we employed this tool to detect occult atherosclerosis caused by breast RT.

Methods: We evaluated 20 asymptomatic patients, less than 60 years of age, treated with RT at least 5 years prior to enrollment. Nine received RT to the left and 11 to the right hemithorax. Average interval between RT and CT was 7.7 years (5-14). All patients were treated with external beam RT using tangential technique. The breast was treated to a dose of 4500-5040 cGy and the tumor bed was boosted to a total dose of 6000-6600 cGy. All patients underwent EBCT to compute the volumetric and agatston calcium scores in the coronary arteries and the aorta.

Results: Of the 11 patients who had RT to right hemithorax, 8 had calcium score of 0, 2 had very minimally elevated scores and 1 had significantly elevated score (patient 19, interval -14 years). Of the 9 patients who had RT to left hemithorax, 7 had calcium score of 0. None had significantly elevated scores. In the aorta, 11 patients had score of 0 and 8 had minimally elevated scores.

Conclusions: Occult atherosclerosis was not detected using EBCT calcium scores in coronaries and aorta in a significant number of patients treated with RT for breast cancer. However, the study is limited by a small sample size.

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Utility of serial urinalyses and urinary cytology in the evaluation of patients with microscopic haematuria

BACKGROUND

Serial urinalyses have been advocated when haematuria is suspected.

OBJECTIVE

To determine the utility of serial urinalyses and urinary cytology in patients presenting for evaluation of microscopic haematuria.

METHODS

Eighty-five patients with the diagnosis of microscopic haematuria were evaluated at a tertiary-care hospital. All patients had a comprehensive urologic evaluation. Clinic and hospital records were reviewed for key factors (e.g., demographic, pathology, radiologic findings and operative findings).

RESULTS

One hundred ninety total urinalyses were reviewed. Eighty-eight (46%) urinalyses were classified as normal, 87 (46%) as haematuria (> 3 RBC/hpf), and 15 (8%) as pyuria/ bacteriuria. The initial urinalysis detected haematuria in 95% of the patients. The addition of the second and third urinalyses detected haematuria in the remaining 5% of the patients with haematuria. Aetiologic factors for microscopic haematuria include urolithiasis 15 (18%), infection 9 (11%) and bladder lesion/tumor 6 (7%). In this setting of microscopic haematuria, urinary cytology was not able to detect any of the five documented bladder tumors. Fifty-seven percent of patients had a negative haematuria evaluation.

CONCLUSION

In the evaluation of the patient with microscopic haematuria, serial urinalyses may have a low yield. Further prospective studies are needed to further evaluate serial urinalyses in this cohort.

Pharmacokinetics and pharmacodynamics of dapagliflozin, a novel selective inhibitor of sodium-glucose co-transporter type 2, in Japanese subjects without and with type 2 diabetes mellitus

AIMS

Dapagliflozin, a selective, orally active inhibitor of the renal sodium-glucose co-transporter type 2 (SGLT2) is in development for the treatment of type 2 diabetes mellitus (T2DM). Here, the pharmacokinetics (PK) and pharmacodynamics (PD) of dapagliflozin were evaluated in healthy Japanese subjects and in Japanese subjects with T2DM.

METHODS

Two studies were conducted: a single-ascending dose (SAD) study (2.5-50 mg) in 32 healthy subjects and a multiple-ascending dose (MAD) study (2.5-20 mg QD for 14 days) in 36 subjects with T2DM. Safety and tolerability were assessed in both studies. Single and multiple dose PK of dapagliflozin and its inactive major metabolite, dapagliflozin 3-O-glucuronide, and PD (urinary glucose parameters) were characterized. Plasma glucose parameters were assessed over 14 days in the MAD study.

RESULTS

No serious adverse events or discontinuations due to adverse events occurred in either study. In healthy and T2DM subjects, dapagliflozin was rapidly absorbed with a time to maximum plasma concentration of 0.5-1.3 h. Systemic exposure of dapagliflozin and dapagliflozin 3-O-glucuronide, measured by maximum plasma concentration and area under the plasma concentration-time curve, increased proportional to dose. On a molar basis, systemic exposure to dapagliflozin 3-O-glucuronide was similar to parent dapagliflozin. There was a dose-related increase in the amount of glucose excreted in the urine (SAD and MAD), which was associated with dose-related decreases in plasma glucose parameters in subjects with T2DM (MAD).

CONCLUSIONS

Dapagliflozin was well tolerated and showed predictable dose-proportional PK and PD parameters in both healthy and T2DM Japanese subjects.

GCIP Is a Tumor Suppressor in Breast Cancer

Background: GCIP protein is a HLH-leucine zipper (HLH-LZ) proteins without basic DNA-binding region, which was identified to be a cyclin D1-binding protein and also was recognized as a human homologue of MAID protein (HHM). Recently, GCIP was found to function as a tumor suppressor in liver and colon tumorigenesis. In this study, we examined in vitro the functional role of GCIP in various breast cancer cell lines.Material and Methods: GCIP-directed siRNA construct was prepared and stable downregulation of GCIP in epithelial-like and nonaggressive/differentiated breast cancer cell line, MCF-7, were selected. In addition, two aggressive/ invasive breast cancer cells (MDA-MB231 and MDA-MB435s) that exhibit low levels of endogenous GCIP expression were transfected with p3x-GCIP-flag, respectively and stable GCIP-re-expressing transfectants were selected. The phalloidin staining cell morphology and functional assays with these stable GCIP downregulating or GCIP re-expressing were performed to characterize the biological effects of GCIP.Results: Stable MCF-7 cells with down-regulated GCIP expression acquired a mesenchymal-like shape and exhibited increased colony formation, migration and invasion capabilities. Furthermore, this was found to be associated with the loss of membrane E-cadherin and increased expression of the mescenchymal marker vimentin. In addition, both the stable MDA-MB231 and MDA-MB435s with GCIP-re-expression acquired an epithelial-like shape and exhibited decreased colony formation, migration and invasion capabilities.Conclusion: our previous study found that decreased expression of GCIP in breast carcinomas compared with normal ductal epithelium (P < 0.001). In this study, we present evidence that GCIP inactivation contributes to the enhanced migratory and invasive capacity of MCF-7 and that GCIP re-expression inhibits a wild range of cellular functions related to the malignant properties of MDA-MB231 and MDA-MB435s, confirming that GCIP is a tumor suppressor in breast cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3158.

Differential regulation of human PlGF gene expression in trophoblast and nontrophoblast cells by oxygen tension

OBJECTIVE

To determine the mechanism for differential effects of low oxygen tension on human PlGF gene transcription in trophoblast and nontrophoblast cells.

STUDY DESIGN

Human PlGF reporter clones and real-time RT-PCR were used to compare the effects of hypoxia on gene transcription in human trophoblast and nontrophoblast cell lines. Overexpression of HIF-1alpha, inhibition of HIF-1 function and biochemical assessments of HIF-1 co-factor interactions were used to characterize hypoxia response mechanisms regulating PlGF transcription.

RESULTS

PlGF transcription is specifically inhibited by low oxygen tension in trophoblast but is induced in some nontrophoblast cells. Overexpression of HIF-1alpha in normoxic cells or inhibition of HIF-1 function in hypoxic cells did not significantly alter transcription patterns of the PlGF gene in either cell type.

CONCLUSIONS

These results suggest that transcriptional repression of PlGF gene expression occurs in human trophoblast exposed to low oxygen tension but that PlGF transcription is stimulated in certain hypoxic nontrophoblast cells. However, regulation of PlGF transcription is not mediated by functional HIF-1 activity in either cell type.