Treatment-induced cell cycle kinetics dictate tumor response to chemotherapy

Toxicity of Orthodontic Brackets Examined by Single Cell Tracking

Subtle toxic effects may be masked in traditional assays that average or summate the response of thousands of cells. We overcome this by using the recent method of single cell tracking in time-lapse recordings. This follows the fate and behavior of individual cells and their progeny and provides unambiguous results for multiple simultaneous biological responses. Further, single cell tracking permits correlation between progeny relationships and cell behavior that is not otherwise possible, including disruption by toxins and toxicants of similarity between paired sister cells. Notably, single cell tracking seems not to have been previously used to study biomaterials toxicity. The culture medium was pre-conditioned by 79 days incubation with orthodontic brackets from seven separate commercial sources. Metal levels were determined by Inductively Coupled Plasma Mass Spectrometry. Metal levels varied amongst conditioned media, with elevated Cr, Mn, Ni, and Cu and often Mo, Pb, Zn, Pd, and Ag were occasionally found. The effect on human dermal fibroblasts was determined by single cell tracking. All bracket-conditioned media reduced cell division (p < 0.05), while some reduced cell migration (p < 0.05). Most bracket-conditioned media increased the rate of asynchronous sister cell division (p < 0.05), a seemingly novel measure for toxicity. No clear effect on cell morphology was seen. We conclude that orthodontic brackets have cytotoxic effects, and that single cell tracking is effective for the study of subtle biomaterials cytotoxicity.

[Effects of L-asparaginase on proliferation, cell cycle and apoptosis of Burkitt lymphoma cell lines]

Objective: To investigate the effect of L-asparaginase on the proliferation, cell cycle, and apoptosis of Burkitt lymphoma cell lines and explore the molecular mechanism. Methods: The effect of L-asparaginase on the cell proliferation of Burkitt lymphoma cell lines was detected using the CCK-8 method. The apoptosis rate and cell cycle were detected using flow cytometry. The expression of related molecules in cell cycle, apoptosis, autophagy, and PI3K/Akt/mTOR signaling pathway was detected and analyzed using qPCR and Western blot assay. Results: L-asparaginase significantly inhibited the proliferation of Burkitt lymphoma cell lines and caused cell cycle arrest at G(0)/G(1) phage. L-asparaginase induced cell apoptosis and autophagy in Burkitt lymphoma cell lines. Further results showed that L-asparaginase inhibited the expression of c-Myc and also inhibited the expression of p-PI3K, p-Akt-S473, p-mTOR, p-70S6K, and p-4E-BP1. Combining PI3K inhibitor LY294002 with L-asparaginase further induced apoptosis. Additionally, L-Asp inhibited STAT and ERK signaling pathways. Conclusion: L-asparaginase inhibited Burkitt lymphoma cell proliferation, arrested cell cycle, activated autophagy, and induced apoptosis by inhibiting the PI3K/Akt/mTOR signaling pathway.

A machine learning approach for single cell interphase cell cycle staging

The cell nucleus is a tightly regulated organelle and its architectural structure is dynamically orchestrated to maintain normal cell function. Indeed, fluctuations in nuclear size and shape are known to occur during the cell cycle and alterations in nuclear morphology are also hallmarks of many diseases including cancer. Regrettably, automated reliable tools for cell cycle staging at single cell level using in situ images are still limited. It is therefore urgent to establish accurate strategies combining bioimaging with high-content image analysis for a bona fide classification. In this study we developed a supervised machine learning method for interphase cell cycle staging of individual adherent cells using in situ fluorescence images of nuclei stained with DAPI. A Support Vector Machine (SVM) classifier operated over normalized nuclear features using more than 3500 DAPI stained nuclei. Molecular ground truth labels were obtained by automatic image processing using fluorescent ubiquitination-based cell cycle indicator (Fucci) technology. An average F1-Score of 87.7% was achieved with this framework. Furthermore, the method was validated on distinct cell types reaching recall values higher than 89%. Our method is a robust approach to identify cells in G₁ or S/G₂ at the individual level, with implications in research and clinical applications.

Doxorubicin treatment modulates chemoresistance and affects the cell cycle in two canine mammary tumour cell lines

BACKGROUND

Doxorubicin (DOX) is widely used in both human and veterinary oncology although the onset of multidrug resistance (MDR) in neoplastic cells often leads to chemotherapy failure. Better understanding of the cellular mechanisms that circumvent chemotherapy efficacy is paramount. The aim of this study was to investigate the response of two canine mammary tumour cell lines, CIPp from a primary tumour and CIPm, from its lymph node metastasis, to exposure to EC50(20h) DOX at 12, 24 and 48 h of treatment. We assessed the uptake and subcellular distribution of DOX, the expression and function of P-glycoprotein (P-gp) and Breast Cancer Resistance Protein (BCRP), two important MDR mediators. To better understand this phenomenon the effects of DOX on the cell cycle and Ki67 cell proliferation index and the expression of p53 and telomerase reverse transcriptase (TERT) were also evaluated by immunocytochemistry (ICC).

RESULTS

Both cell lines were able to uptake DOX within the nucleus at 3 h treatment while at 48 h DOX was absent from the intracellular compartment (assessed by fluorescence microscope) in all the surviving cells. CIPm, originated from the metastatic tumour, were more efficient in extruding P-gp substrates. By ICC and qRT-PCR an overall increase in both P-gp and BCRP were observed at 48 h of EC50(20h) DOX treatment in both cell lines and were associated with a striking increase in the percentage of p53 and TERT expressing cells by ICC. The cell proliferation fraction was decreased at 48 h in both cell lines and cell cycle analysis showed a DOX-induced arrest in the S phase for CIPp, while CIPm had an increase in cellular death without arrest. Both cells lines were therefore composed by a fraction of cells sensible to DOX that underwent apoptosis/necrosis.

CONCLUSIONS

DOX administration results in interlinked modifications in the cellular population including a substantial effect on the cell cycle, in particular arrest in the S phase for CIPp and the selection of a subpopulation of neoplastic cells bearing MDR phenotype characterized by P-gp and BCRP expression, TERT activation, p53 accumulation and decrease in the proliferating fraction. Important information is given for understanding the dynamic and mechanisms of the onset of drug resistance in a neoplastic cell population.

Expression of miR-652-3p and Effect on Apoptosis and Drug Sensitivity in Pediatric Acute Lymphoblastic Leukemia

MicroRNAs (miRNAs) expression profiles were screened in plasma samples from pediatric patients with acute lymphoblastic leukemia (ALL) and healthy controls, using qRT-PCR-based TaqMan low-density miRNA arrays. MiR-652-3p (a circulating miRNA) was downregulated in new diagnosis (ND) patients compared with healthy controls. The levels of miR652-3p were restored in complete remission (CR) but were downregulated again in disease relapse (RE). The expression pattern of miR-652-3p was validated in bone marrow (BM) samples from other pediatric ALL patients. MiR-652-3p was significantly upregulated in BM when the patients (n=86) achieved CR, as compared with the matched ND samples (p<0.001). Moreover, the miR-652-3p levels in BM decreased again in two patients at RE. In addition, the lymphoblastic leukemia cell lines Reh and RS4:11 were found to have lower levels of miR-625-3p than the normal B-cell line. Overexpression of miR-652-3p using agomir increased the sensitivity to vincristine and cytarabine (all p<0.05) and promoted apoptosis (both p<0.05) in Reh and RS4:11 cells. In conclusion, the results suggested that a low level of miR-652-3p might be involved in the pathogenesis of pediatric ALL. Overexpression of miR-652-3p might suppress lymphoblastic leukemia cells, promoting apoptosis and increasing sensitivity to chemotherapeutic drugs.

Genome-wide transcriptional analysis of BRD4-regulated genes and pathways in human glioma U251 cells

Bromodomain containing 4 (BRD4), a member of the bromodomain and extra-terminal family, has become a promising drug target for numerous types of cancer. BRD4 has been reported to be deregulated in gliomas; however, the precise molecular pathways regulated by BRD4 remained elusive. In the present study, BRD4 expression was silenced in the glioma cell line U251 and the results demonstrated that BRD4 knockdown attenuated cell proliferation and promoted cell apoptosis. A genome-wide analysis of BRD4-regulated transcripts in U251 cells was performed using microarray to reveal the possible molecular mechanism. A total of 3,529 differentially expressed genes were identified; 1,648 of these genes were upregulated and 1,881 were downregulated. The results of the gene ontology analysis revealed that these genes were mainly involved in membrane organization, mitotic cell cycle, cell division and DNA replication. Pathway analysis revealed that the pathways altered following BRD4 knockdown included multiple cellular processes, such as cell cycle and apoptosis. Candidate genes were identified through global signal transduction network analysis and were validated using reverse transcription-quantitative polymerase chain reaction and western blot analyses. The results demonstrated that BRD4 knockdown decreased the expression of KRAS proto-oncogene GTPase (KRAS). Downregulated KRAS expression in U251 cells restrained cell proliferation and promoted cell apoptosis, suggesting that the effect of BRD4 on glioma cells might occur through the Ras pathway. In conclusion, the present results confirmed the role of BRD4 in glioma and provided information for further exploration of the molecular mechanism of BRD4 in glioma development and progression.

Miki (Mitotic Kinetics Regulator) Immunoexpression in Normal Liver, Cirrhotic Areas and Hepatocellular Carcinomas: a Preliminary Study with Clinical Relevance

Hepatocellular carcinoma (HCC) is the most common type of primary malignant tumor in the liver. One of the main features of cancer survival is the generalized loss of growth control exhibited by cancer cells, and Miki is a protein related to the immunoglobulin superfamily that plays an important role in mitosis. We aim to study protein expression levels of Miki in non-tumoral liver and 20 HCCs recruited from a Pathology Department. Clinical information was also obtained. A tissue microarray was performed, and immunohistochemical techniques applied to study protein expression levels of Miki. In normal liver, Miki was weakly expressed, showing nuclear staining in the hepatocytes. Cirrhotic areas and HCCs showed a variety of staining patterns. Most HCC samples showed positive expression, with three different staining patterns being discernible: nuclear, cytoplasmic and mixed. Statistical analysis showed a significant association between grade of differentiation, Ki-67 proliferative index, survival rates and staining patterns. This study has revealed the positive expression of Miki in normal liver, cirrhotic areas and HCCs. Three different staining patterns of Miki expression with clinical relevance were noted in HCCs.

Knockdown of hnRNP A2/B1 inhibits cell proliferation, invasion and cell cycle triggering apoptosis in cervical cancer via PI3K/AKT signaling pathway

Cervical cancer is currently one of the major threats to women's health. The overexpression of heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNP A2/B1) as the biomarker has been investigated in various cancers. In our previous study, we found that lobaplatin induced apoptosis and cell cycle arrest via downregulation of proteins including hnRNP A2/B1 in cervical cancer cells. However, the underlying relationship between hnRNP A2/B1 and cervical cancer remained largely unknown. hnRNP A2/B1 knock-down in HeLa and CaSki cells was performed by shRNA transfection. The expression of hnRNP A2/B1 was detected by western blot and Quantitative Real-time PCR. Cell proliferation, migration, invasion and the IC₅₀ of lobaplatin and irinotecan were determined by MTT assay, Transwell assay, Plate colony formation assay and wound healing assay. Flow cytometry was perfomed to investigate cell apoptosis and the cell cycle. The expression of PI3K, AKT, p-AKT, p21, p27, caspase-3, cleaved caspase-3 were revealed by western blot. Nude mouse xenograft model was undertaken with HeLa cells and the xenograft tumor tissue samples were analyzed for the expression of PCNA and Ki-67 by immunohistochemistry and the cell morphology was evaluated by hematoxylin and eosin (H&E). Results revealed that hnRNP A2/B1 was successfully silenced in HeLa and CaSki cells. hnRNP A2/B1 knock-down significantly induced the suppression of proliferation, migration, invasion and also enhancement of apoptosis and reduced the IC₅₀ of lobaplatin and irinotecan. The expression of p21, p27 and cleaved caspase-3 in shRNA group were significantly upregulated and the expression of p-AKT was reduced both in vitro and in vivo. The results of immunohistochemistry showed that PCNA and Ki-67 were significantly downregulated in vivo. The growth of nude mouse xenograft tumor was significantly reduced by hnRNP A2/B1 knock-down. Taken together, these data indicate that inhibition of hnRNP A2/B1 in cervical cancer cells can inhibit cell proliferation and invasion, induce cell-cycle arrestment and trigger apoptosis via PI3K/AKT signaling pathway. In addition, after silencing hnRNP A2/B1 can increase the sensitivity of cervical cancer cells to lobaplatin and irinotecan.

Genome and transcriptome delineation of two major oncogenic pathways governing invasive ductal breast cancer development

Invasive ductal carcinoma (IDC) is a major histo-morphologic type of breast cancer. Histological grading (HG) of IDC is widely adopted by oncologists as a prognostic factor. However, HG evaluation is highly subjective with only 50%-85% inter-observer agreements. Specifically, the subjectivity in the assignment of the intermediate grade (histologic grade 2, HG2) breast cancers (comprising ~50% of IDC cases) results in uncertain disease outcome prediction and sub-optimal systemic therapy. Despite several attempts to identify the mechanisms underlying the HG classification, their molecular bases are poorly understood.We performed integrative bioinformatics analysis of TCGA and several other cohorts (total 1246 patients). We identified a 22-gene tumor aggressiveness grading classifier (22g-TAG) that reflects global bifurcation in the IDC transcriptomes and reclassified patients with HG2 tumors into two genetically and clinically distinct subclasses: histological grade 1-like (HG1-like) and histological grade 3-like (HG3-like). The expression profiles and clinical outcomes of these subclasses were similar to the HG1 and HG3 tumors, respectively. We further reclassified IDC into low genetic grade (LGG = HG1+HG1-like) and high genetic grade (HGG = HG3-like+HG3) subclasses. For the HG1-like and HG3-like IDCs we found subclass-specific DNA alterations, somatic mutations, oncogenic pathways, cell cycle/mitosis and stem cell-like expression signatures that discriminate between these tumors. We found similar molecular patterns in the LGG and HGG tumor classes respectively.Our results suggest the existence of two genetically-predefined IDC classes, LGG and HGG, driven by distinct oncogenic pathways. They provide novel prognostic and therapeutic biomarkers and could open unique opportunities for personalized systemic therapies of IDC patients.

Antitumor effects and the underlying mechanism of licochalcone A combined with 5-fluorouracil in gastric cancer cells

Licochalcone A (LCA) is a flavonoid extracted from licorice root that has antiparasitic, antibacterial and antitumor properties. Previous studies have revealed that LCA may be a novel treatment for gastric cancer. The present study further assessed the potential antitumor effects of LCA alone or in combination with 5-fluorouracil (5-FU), and the underlying mechanisms responsible for those effects in gastric cancer cells. The effects of LCA alone or in combination with 5-FU on SGC7901 and MKN-45 gastric cancer cell lines were studied using Cell Counting Kit-8, cell cycle, apoptosis and western blot analyses of cell check points and apoptosis-associated proteins. The results revealed that LCA inhibited cell proliferation, blocked cell cycle progression at the G₂/M transition and induced apoptosis. Western blot analysis demonstrated that LCA treatment increased the levels of tumor proteins 21 and 27, as well as mouse double minute 2 homolog in gastric cancer cells. In addition, LCA treatment increased the expression levels of Bax, cleaved-poly ADP ribose polymerase, tumor protein 53 and caspase 3, and decreased the expression levels of Bcl-2. Therefore, the present study demonstrated that LCA alone or in combination with 5-FU may have significant anticancer effects on gastric cancer cells, and may be a novel therapeutic for the treatment of gastric cancer in the future.

Quantifying intrinsic and extrinsic control of single-cell fates in cancer and stem/progenitor cell pedigrees with competing risks analysis

The molecular control of cell fate and behaviour is a central theme in biology. Inherent heterogeneity within cell populations requires that control of cell fate is studied at the single-cell level. Time-lapse imaging and single-cell tracking are powerful technologies for acquiring cell lifetime data, allowing quantification of how cell-intrinsic and extrinsic factors control single-cell fates over time. However, cell lifetime data contain complex features. Competing cell fates, censoring, and the possible inter-dependence of competing fates, currently present challenges to modelling cell lifetime data. Thus far such features are largely ignored, resulting in loss of data and introducing a source of bias. Here we show that competing risks and concordance statistics, previously applied to clinical data and the study of genetic influences on life events in twins, respectively, can be used to quantify intrinsic and extrinsic control of single-cell fates. Using these statistics we demonstrate that 1) breast cancer cell fate after chemotherapy is dependent on p53 genotype; 2) granulocyte macrophage progenitors and their differentiated progeny have concordant fates; and 3) cytokines promote self-renewal of cardiac mesenchymal stem cells by symmetric divisions. Therefore, competing risks and concordance statistics provide a robust and unbiased approach for evaluating hypotheses at the single-cell level.

Upregulation of the growth arrest-specific-2 in recurrent colorectal cancers, and its susceptibility to chemotherapy in a model cell system

Colorectal cancer (CRC) is one of the most common life-threatening malignances worldwide. CRC relapse markedly decreases the 5-year survival of patients following surgery. Aberrant expression of genes involved in pathways regulating the cell cycle, cell proliferation, or cell death are frequently reported in CRC tumorigenesis. We hypothesized that genes involved in CRC relapse might serve as prognostic indicators. We first evaluated the significance of gene sequences in the feces of patients with CRC relapse by consulting a public database. Tumorigenesis of target tissues was tested through tumor cell growth, cell cycle regulation, and chemotherapeutic efficacy. We found a highly significant correlation between CRC relapse and growth arrest-specific 2 (GAS2) gene expression. Based on cell models, the overexpressed GAS2 was associated with cellular growth rate, cell cycle regulation, and with chemotherapeutic sensitivity. Cell division was impaired by treating cells with 2-[4-(7-chloro-2-quinoxalinyloxy)phenoxy]-propionic acid (XK469), even when the cells were overexpressing GAS2. Thus, downregulation of GAS2 expression might control CRC relapse after curative resection. GAS2 could serve as a noninvasive marker from the feces of patients with prediagnosed CRC. Our findings suggest that GAS2 could have potential clinical applications for predicting early CRC relapse after radical resection, and that XK469 might impair tumor cell division by reducing GAS2 expression or blocking its cellular translocation. This will help in selecting the best therapeutic option, 5-fluorouracil in combination with XK469, for patients overexpressing GAS2 in CRC cells. Thus, GAS2 might act as a prognostic biomolecule and potential therapeutic target in patients with CRC relapse.

p53 Restoration in Induction and Maintenance of Senescence: Differential Effects in Premalignant and Malignant Tumor Cells

The restoration of p53 has been suggested as a therapeutic approach in tumors. However, the timing of p53 restoration in relation to its efficacy during tumor progression still is unclear. We now show that the restoration of p53 in murine premalignant proliferating pineal lesions resulted in cellular senescence, while p53 restoration in invasive pineal tumors did not. The effectiveness of p53 restoration was not dependent on p19(Arf) expression but showed an inverse correlation with Mdm2 expression. In tumor cells, p53 restoration became effective when paired with either DNA-damaging therapy or with nutlin, an inhibitor of p53-Mdm2 interaction. Interestingly, the inactivation of p53 after senescence resulted in reentry into the cell cycle and rapid tumor progression. The evaluation of a panel of human supratentorial primitive neuroectodermal tumors (sPNET) showed low activity of the p53 pathway. Together, these data suggest that the restoration of the p53 pathway has different effects in premalignant versus invasive pineal tumors, and that p53 activation needs to be continually sustained, as reversion from senescence occurs rapidly with aggressive tumor growth when p53 is lost again. Finally, p53 restoration approaches may be worth exploring in sPNET, where the p53 gene is intact but the pathway is inactive in the majority of examined tumors.