Immunocytochemical analysis of cell lines derived from solid tumors

Plasma Rich in Growth Factors in Bone Regeneration: The Proximity to the Clot as a Differential Factor in Osteoblast Cell Behaviour

The osteogenic differentiation process, by which bone marrow mesenchymal stem cells and osteoprogenitors transform into osteoblasts, is regulated by several growth factors, cytokines, and hormones. Plasma Rich in Growth Factors (PRGF) is a blood-derived preparation consisting of a plethora of bioactive molecules, also susceptible to containing epigenetic factors such as ncRNAs and EVs, that stimulates tissue regeneration. The aim of this study was to investigate the effect of the PRGF clot formulation on osteogenic differentiation. Firstly, osteoblast cells were isolated and characterised. The proliferation of bone cells cultured onto PRGF clots or treated with PRGF supernatant was determined. Moreover, the gene expression of Runx2 (ID: 860), SP7 (ID: 121340), and ALPL (ID: 249) was analysed by one-step real-time quantitative polymerase chain reaction (RT-qPCR). Additionally, alkaline phosphatase (ALPL) activity determination was performed. The highest proliferative effect was achieved by the PRGF supernatant in all the study periods analysed. Concerning gene expression, the logRGE of Runx2 increased significantly in osteoblasts cultured with PRGF formulations compared with the control group, while that of SP7 increased significantly in osteoblasts grown on the PRGF clots. On the other hand, despite the fact that the PRGF supernatant induced ALPL up-regulation, significantly higher enzyme activity was detected for the PRGF clots in comparison with the supernatant formulation. According to our results, contact with the PRGF clot could promote a more advanced phase in the osteogenic process, associated to higher levels of ALPL activity. Furthermore, the PRGF clot releasate stimulated a higher proliferation rate in addition to reduced SP7 expression in the cells located at a distant ubication, leading to a less mature osteoblast stage. Thus, the spatial relationship between the PRGF clot and the osteoprogenitors cells could be a factor that influences regenerative outcomes.

Co-dependent regulation of p-BRAF and potassium channel KCNMA1 levels drives glioma progression

BRAF mutations have been found in gliomas which exhibit abnormal electrophysiological activities, implying their potential links with the ion channel functions. In this study, we identified the Drosophila potassium channel, Slowpoke (Slo), the ortholog of human KCNMA1, as a critical factor involved in dRaf^GOF glioma progression. Slo was upregulated in dRaf^GOF glioma. Knockdown of slo led to decreases in dRaf^GOF levels, glioma cell proliferation, and tumor-related phenotypes. Overexpression of slo in glial cells elevated dRaf expression and promoted cell proliferation. Similar mutual regulations of p-BRAF and KCNMA1 levels were then recapitulated in human glioma cells with the BRAF mutation. Elevated p-BRAF and KCNMA1 were also observed in HEK293T cells upon the treatment of 20 mM KCl, which causes membrane depolarization. Knockdown KCNMA1 in these cells led to a further decrease in cell viability. Based on these results, we conclude that the levels of p-BRAF and KCNMA1 are co-dependent and mutually regulated. We propose that, in depolarized glioma cells with BRAF mutations, high KCNMA1 levels act to repolarize membrane potential and facilitate cell growth. Our study provides a new strategy to antagonize the progression of gliomas as induced by BRAF mutations.

Challenges and Opportunities for Immunoprofiling Using a Spatial High-Plex Technology: The NanoString GeoMx® Digital Spatial Profiler

Characterization of the tumor microenvironment through immunoprofiling has become an essential resource for the understanding of the complex immune cell interactions and the assessment of biomarkers for prognosis and prediction of immunotherapy response; however, these studies are often limited by tissue heterogeneity and sample size. The nanoString GeoMx^® Digital Spatial Profiler (DSP) is a platform that allows high-plex profiling at the protein and RNA level, providing spatial and temporal assessment of tumors in frozen or formalin-fixed paraffin-embedded limited tissue sample. Recently, high-impact studies have shown the feasibility of using this technology to identify biomarkers in different settings, including predictive biomarkers for immunotherapy in different tumor types. These studies showed that compared to other multiplex and high-plex platforms, the DSP can interrogate a higher number of biomarkers with higher throughput; however, it does not provide single-cell resolution, including co-expression of biomarker or spatial information at the single-cell level. In this review, we will describe the technical overview of the platform, present current evidence of the advantages and limitations of the applications of this technology, and provide important considerations for the experimental design for translational immune-oncology research using this tissue-based high-plex profiling approach.

MMP12 is a potential therapeutic target for Adamantinomatous craniopharyngioma: Conclusions from bioinformatics analysis and in vitro experiments

Adamantinomatous craniopharyngioma (ACP) is considered a benign intracranial tumor, but it can also exhibit aggressive characteristics. Due to its unique location in the suprasellar, which brings it close to important nerves and vascular structures, ACP can often lead to significant neuroendocrine diseases. The current treatments primarily include surgical intervention, radiation therapy or a combination of the two, but these can lead to serious complications and adversely affect the quality of life of patients. Thus, it is important to identify effective and safe alternatives. Recently, studies have focused on the tumor genome, transcriptome and proteome in an attempt to identify potential therapeutic targets for clinical use. However, studies on this region of the CP are limited; thus, the present study focused on this region. The GSE94349 and GSE68015 datasets were downloaded from the Gene Expression Omnibus database and analyzed. In the in vitro studies, the effect of the matrix metalloproteinase (MMP)12 inhibitor, MMP408, on cell proliferation and protein expression was assessed. The results demonstrated that MMP408 effectively inhibited cell proliferation and migration of ACP cells, and decreased the expression levels of the related proteins. Thus, MMP12 may be used as a potential therapeutic target for the treatment of ACP.

ERK Activation Modulates Cancer Stemness and Motility of a Novel Mouse Oral Squamous Cell Carcinoma Cell Line

We established the NHRI-HN1 cell line from a mouse tongue tumor induced by 4-nitroquinoline 1-oxide (4-NQO)/arecoline, with further selection for cell stemness via in vitro sphere culture, to evaluate potential immunotherapies for oral squamous cell carcinoma (OSCC) in East and Southeast Asia. In vivo and in vitro phenotypic characterization, including tumor growth, immune modulator administration, gene expression, morphology, migration, invasion, and sphere formation assays, were conducted. NHRI-HN1 cells are capable of generating orthotopic tumors in syngeneic mice. Interestingly, immune stimulation via CpG oligodeoxynucleotide (CpG-ODN) dramatically reduced the tumor growth in NHRI-HN1 cell-injected syngeneic mice. The pathways enriched in genes that were differentially expressed in NHRI-HN1 cells when compared to non-tumorigenic cells were similar to those that were identified when comparing human OSCC and non-tumorous tissues. NHRI-HN1 cells have characteristics of epithelial-mesenchymal transition (EMT), including enhanced migration and invasion. NHRI-HN1 cells showed aggressive cell growth and sphere formation. The blockage of extracellular signal-regulated kinase (ERK) activation suppressed cell migration and reduced stemness characteristics in NHRI-HN1 cells, similar to human OSCC cell lines. Our data suggest that NHRI-HN1 cells, showing tumorigenic characteristics of EMT, cancer stemness, and ERK activation, are sufficient in modeling human OSCC and also competent for use in investigating oral cancer immunotherapies.

Condition mimicking peritoneal metastasis associated with preoperative staging laparoscopy in advanced gastric cancer

Preoperative staging laparoscopy is used to search for peritoneal dissemination or distant metastasis as part of the treatment strategy for advanced gastric cancer. We observed pseudo-peritoneal metastasis during laparotomy in 6 of 49 patients in whom lack of peritoneal dissemination had been confirmed by preoperative staging laparoscopy. In all cases, suspected nodules were biopsied and subjected to rapid histological diagnosis. However, a definite malignant or benign diagnosis could not be obtained via a rapid histological examination during surgery. A final histological examination combined with immunohistological analysis using formalin-fixed embedded tissues confirmed no malignancy after surgery in all cases. These rapidly growing nodules that mimic peritoneal metastasis are thought to be associated with the use of grasping forceps during staging laparoscopy. No cases have been reported in which peritoneal nodules mimicking peritoneal metastasis occurred after staging laparoscopy, and surgeons should consider this possibility in patients treated shortly after staging laparoscopy.

CXCL12/CXCR4 promotes proliferation, migration, and invasion of adamantinomatous craniopharyngiomas via PI3K/AKT signal pathway

OBJECTIVES

Adamantinomatous craniopharyngiomas (adaCP) accounts for 5.6% to 15% of intracranial tumors. High expression of chemokine (C-X-C motif) ligand 12 (CXCL12, also known as stromal cell-derived factor 1 [SDF1]) and its receptor CXC receptor type 4 (CXCR4) are widespread in various malignancy via multiple signal transduction pathways. This study aims to investigate the mechanism of CXCL12/CXCR4 promoting proliferation, migration, and invasion of adaCP.

METHODS

Quantitative real-time polymerase chain reaction, Western blot analysis, and immunohistochemistry were used to evaluate the expression of CXCL12/CXCR4 mRNA and protein in 10 human adaCP tissues. Three successfully primary cell lines were obtained from native mainly solid tumor specimens, and confirmed by the means of inverted contrast microscope directly and following hematoxylin and eosin staining. Immunofluorescence was used to detect protein expression in vivo for the verification of primary cell line. Proliferation, migration, and invasion assays were performed to assess the biological functional role of CXCL12/CXCR4 in adaCP. The signal pathways involved in the action of CXCL12/CXCR4 in adaCP were also evaluated.

RESULTS

CXCL12 and CXCR4 were highly expressed in human adaCP samples. Primary adaCP cells were isolated and detected by the means of immunofluorescence for the detection of pan cytokeratin (pan-CK) and vimentin (VIM). Overexpression of CXCL12/CXCR4 significantly promoted the proliferation, migration, and invasion of primary adaCP cells. Moreover, cancer-promoting activity of CXCL12/CXCR4 is partially through its facilitation of PI3K/AKT signal pathway.

CONCLUSIONS

Our data showed that CXCL12/CXCR4 promotes adaCP proliferation, migration, and invasion through PI3K/AKT signal pathway. These findings suggested that therapeutic strategies regulating CXCL12/CXCR4 expression may provide an effective treatment of adaCP.

Cross-contamination of the human salivary gland HSG cell line with HeLa cells: A STR analysis study

OBJECTIVES

The human salivary gland (HSG) cell line, labeled as a submandibular ductal cell line, is commonly used as in vitro models to study radiation therapy, Sjögren's syndrome, pleomorphic adenoma, mucocele, epithelial-to-mesenchymal transition, and epigenetics. However, the American Type Culture Collection (ATCC) has recently released a list of cross-contaminated cell lines that included HSG. Despite this notice, some research laboratories still use HSG as a salivary cell model. Therefore, this study examined the authenticity of HSG sampled from three different laboratories.

METHODS

DNA was extracted from HSG and additional salivary cell lines (NS-SV-AC, NS-SV-DC, A253, HSY) and submitted for cell line authentication with short tandem repeat (STR) analysis.

RESULTS

All HSG samples had STR profiles indicating >80% match with HeLa in both the ATCC and Deutsche Sammlung von Mikroorganismen und Zellkulturen (DSMZ) databases. This confirmed that HSG sampled from three different laboratories and HSY shared a common ancestry (host) with HeLa, whereas NS-SV-AC, NS-SV-DC, and A253 had unique STR profiles.

CONCLUSION

Short tandem repeat analysis revealed that HSG was contaminated by the HeLa cell line. Furthermore, because genotyping of the original HSG cell line was not performed during its establishment, it will be difficult to authenticate an uncontaminated sample of HSG.

Immunohistochemical Characterization and Sensitivity to Human Adenovirus Serotypes 3, 5, and 11p of New Cell Lines Derived from Human Diffuse Grade II to IV Gliomas

BACKGROUND

Oncolytic adenoviruses show promise in targeting gliomas because they do not replicate in normal brain cells. However, clinical responses occur only in a subset of patients. One explanation could be the heterogenic expression level of virus receptors. Another contributing factor could be variable activity of tumor antiviral defenses in different glioma subtypes.

METHODS

We established a collection of primary low-passage cell lines from different glioma subtypes (3 glioblastomas, 3 oligoastrocytomas, and 2 oligodendrogliomas) and assessed them for receptor expression and sensitivity to human adenovirus (HAd) serotypes 3, 5, and 11p. To gauge the impact of antiviral defenses, we also compared the infectivity of the oncolytic adenoviruses in interferon (IFN)-pretreated cells with IFN-sensitive Semliki Forest virus (SFV).

RESULTS

Immunostaining revealed generally low expression of HAd5 receptor CAR in both primary tumors and derived cell lines. HAd11p receptor CD46 levels were maintained at moderate levels in both primary tumor samples and derived cell lines. HAd3 receptor DSG-2 was reduced in the cell lines compared to the tumors. Yet, at equal multiplicities of infection, the oncolytic potency of HAd5 in vitro in tumor-derived cells was comparable to HAd11p, whereas HAd3 lysed fewer cells than either of the other two HAd serotypes in 72 hours. IFN blocked replication of SFV, while HAds were rather unaffected.

CONCLUSIONS

Adenovirus receptor levels on glioma-derived cell lines did not correlate with infection efficacy and may not be a relevant indicator of clinical oncolytic potency. Adenovirus receptor analysis should be preferentially performed on biopsies obtained perioperatively.

Establishment and genomic characterization of primary salivary duct carcinoma cell line

OBJECTIVES

To develop and characterize in vitro salivary duct carcinoma as a surrogate for functional studies.

MATERIALS AND METHODS

Cells were dispersed from tumor tissue fragments under sterile conditions in RPMI media. Disassociated cells were cultivated, immortalized with hTERT and propagated for more than 100 passages. Morphologic, linage, cytogenetic and genomic analyses were performed on different passages of cell line and primary tumor. Soft agar growth was performed.

RESULTS

Analysis of cytomorphologic features, growth characteristics and lineage specific markers expression confirmed the epithelial derivation and the neoplastic nature of the cell line. DNA STRs analysis showed identical match of both cell line and primary tumor. Cultivated cells expressed Androgen Receptor (AR), PTEN, and EFGR proteins and the AR-V7 isoform transcript. Comparative exome-sequencing identified common mutated genes in both cell line and primary tumor. In-vitro colony formation of late passages is established.

CONCLUSION

We report the development of the first human salivary duct carcinoma cell line (MDA-SDC-04) that retains critical biological and genomic features of the donor tumor.

The human ovarian cancer cell line CABA I: A peculiar genetic evolution

The objective of this study was to study the human ovarian cancer cell line CABA I by means of short tandem repeats (STR) profiling and cytogenetic analysis in order to prevent future misidentification or cross-contamination and verify its stability during in vitro cultivation. To this end, cells at passages 18 and 38 were analyzed using cytogenetic techniques in order to verify possible chromosomal aberrations and the karyotypic evolution of this cell line; GTG-banding and FISH were also performed. For STR analysis, DNA was extracted using the automated extractor MagNA pure and analyzed by means of PowerPlex 16 HS. STR profiles were analyzed by GeneMapper 3.2.1 software. Whereas comparative cytogenetic analysis of CABA I cells at passage 18 and 38 has demonstrated considerable genetic instability, we found that STR profiles were essentially unaltered in both analyzed passages, suggesting that the STR profile is reliable and could be used for the regular authentication of CABA I over time. It should be emphasized, however, that of the 16 loci generally used in human STR profiles, only 3 were properly detectable in CABA I. The data highlight that the CABA I cell line demonstrates an anomalous STR profile that does not fully adjust the criteria currently used for the identification of human cells; in spite of this, it remains stable during the in vitro maintainance. Moreover, the genetic instability of the CABA I cell line overlaps with those observed in vivo in tumor cells, making it a suitable candidate to analyze, in vitro, the peculiar genetic evolution of ovarian cancer cells.

Antiproliferative Action of Conjugated Linoleic Acid on Human MCF-7 Breast Cancer Cells Mediated by Enhancement of Gap Junctional Intercellular Communication through Inactivation of NF- κ B

The major conjugated linoleic acid (CLA) isomers, c9,t11-CLA and t10,c12-CLA, have anticancer effects; however, the exact mechanisms underlying these effects are unknown. Evidence suggests that reversal of reduced gap junctional intercellular communication (GJIC) in cancer cells inhibits cell growth and induces cell death. Hence, we determined that CLA isomers enhance GJIC in human MCF-7 breast cancer cells and investigated the underlying molecular mechanisms. The CLA isomers significantly enhanced GJIC of MCF-7 cells at 40 μM concentration, whereas CLA inhibited cell growth and induced caspase-dependent apoptosis. CLA increased connexin43 (Cx43) expression both at the transcriptional and translational levels. CLA inhibited nuclear factor-κB (NF-κB) activity and enhanced reactive oxygen species (ROS) generation. No significant difference was observed in the efficacy of c9,t11-CLA and t10,c12-CLA. These results suggest that the anticancer effect of CLA is associated with upregulation of GJIC mediated by enhanced Cx43 expression through inactivation of NF-κB and generation of ROS in MCF-7 cells.

Delving into somatic variation in sporadic melanoma

Melanoma, the most aggressive form of skin cancer, has increased in incidence more rapidly than any other cancer. The completion of the human genome project and advancements in genomics technologies has allowed us to investigate genetic alterations of melanoma at a scale and depth that is unprecedented. Here, we survey the history of the different approaches taken to understand the genomics of melanoma - from early candidate genes, to gene families, to genome-wide studies. The new era of whole-exome and whole-genome sequencing has paved the way for an in-depth understanding of melanoma biology, identification of new therapeutic targets, and development of novel personalized therapies for melanoma.

Species identification and authentification of human and rodent cell cultures using polymerase chain reaction analysis of vomeronasal receptor genes

Cell culture and the use of cell lines are routinely used in basic scientific research. It is therefore imperative for researchers to ensure the origin of the cell lines used and that they are routinely re-analysed for contamination and misidentification. Inter-species contamination is relatively frequent, and the most commonly used cell lines are of human, mouse and rat derivation. We have developed simple species specific primer assays based on genomic sequence differences in vomeronasal receptor gene family members to discriminate between human, mouse and rat DNA using standard agarose gel electrophoresis. Furthermore, these PCR assays are able to identify the species composition within an inter-species mixed population. This approach therefore provides a valuable tool to enable a rapid, simple and relatively inexpensive determination of the authentication and contamination of cell cultures.

Keratin 23, a novel DPC4/Smad4 target gene which binds 14-3-3ε

Background

Inactivating mutations of SMAD4 are frequent in metastatic colorectal carcinomas. In previous analyses, we were able to show that restoration of Smad4 expression in Smad4-deficient SW480 human colon carcinoma cells was adequate to suppress tumorigenicity and invasive potential, whereas in vitro cell growth was not affected. Using this cellular model system, we searched for new Smad4 targets comparing nuclear subproteomes derived from Smad4 re-expressing and Smad4 negative SW480 cells.

Methods

High resolution two-dimensional (2D) gel electrophoresis was applied to identify novel Smad4 targets in the nuclear subproteome of Smad4 re-expressing SW480 cells. The identified candidate protein Keratin 23 was further characterized by tandem affinity purification. Immunoprecipitation, subfractionation and immunolocalization studies in combination with RNAi were used to validate the Keratin 23-14-3-3ε interaction.

Results

We identified keratins 8 and 18, heat shock proteins 60 and 70, plectin 1, as well as 14-3-3ε and γ as novel proteins present in the KRT23-interacting complex. Co-immunoprecipitation and subfractionation analyses as well as immunolocalization studies in our Smad4-SW480 model cells provided further evidence that KRT23 associates with 14-3-3ε and that Smad4 dependent KRT23 up-regulation induces a shift of the 14-3-3ε protein from a nuclear to a cytoplasmic localization.

Conclusion

Based on our findings we propose a new regulatory circuitry involving Smad4 dependent up-regulation of KRT23 (directly or indirectly) which in turn modulates the interaction between KRT23 and 14-3-3ε leading to a cytoplasmic sequestration of 14-3-3ε. This cytoplasmic KRT23-14-3-3 interaction may alter the functional status of the well described 14-3-3 scaffold protein, known to regulate key cellular processes, such as signal transduction, cell cycle control, and apoptosis and may thus be a previously unappreciated facet of the Smad4 tumor suppressive circuitry.

Cell line cross-contamination in biomedical research: a call to prevent unawareness

During the 1950s, cross-contamination of cell lines emerged as a problem with serious consequences on the quality of biomedical research. Unfortunately, this situation has worsened over years. In this context, some actions should be urgently undertaken to avoid the generation of misleading data due to the increasingly and sometimes neglected use of cross-contaminated cell lines. Unawareness about this problem may then turn many scientists into victims or even perpetrators of this unwanted situation. Collaborative actions involving researchers, cell banks, journals, and funding agencies are needed to save the scientific reputation as well as many public or private resources that are used to produce misleading data.

Profiling and authentication of human cell lines using short tandem repeat (STR) loci: Report from the National Cell Bank of Iran

Assurance of cell line homogeneity and capability of cell contamination detection are among the most essential steps of cell based research. Due to high discriminatory efficiency, low cost and reliability, analysis of short tandem repeats (STR) has been introduced as a method of choice for human cell line authentication. In the present study 13 Combined DNA Index System (CODIS) based STRs along with the gender determination (Amelogenin) gene were utilized to establish a reproducible approach for the authentication of 100 human cell lines deposited in the National Cell Bank of Iran (NCBI), using the polymerase chain reaction (PCR) method. PCR products were subsequently analyzed by polyacrylamide gel electrophoresis (PAGE) and visualized by silver staining followed by gel documentation and software analysis. STR profiles obtained were compared with those of the American Type Culture Collection (ATCC) and the Japanese Collection of Research Bioresource (JCRB) as STR references. We detected 18.8% cross contamination among the NCBI human cell lines. To our knowledge, this is the first report of authentication of human cell lines using the 13 CODIS core STRs combined with Amelogenin.

Cytogenetic and molecular cytogenetic characterization of the stable ovarian carcinoma cell line (OvBH-1)

Detailed characterization and identification of cancer cell lines is the basis for the credibility of experimental studies. Therefore, chromosomal analysis should be routinely included in the protocol of cell line characterization and in the protocols of experimental studies performed on cell lines. In 2000, our group established and characterized cytomorphologically and immunophenotypically a new cell line, OvBH-1, which was derived from the ascitic fluid cells of an untreated patient with ovarian clear-cell adenocarcinoma. The aim of the current study was to characterize OvBH-1 cytogenetically and to monitor its stability by comparison of morphologic, immunohistochemical, and cytogenetic features between the early (135) and late (385) passages. Conventional and molecular cytogenetic analyses (fluorescence in situ hybridization and spectral karyotyping) of OvBH-1 revealed the following hypotriploid karyotype with random translocations: der(2)t(2;13),der(4)t(4;22), der(5)t(2;5). Complex rearrangements involving chromosomes 3, 15, and 20 were also found. FISH analysis with a p53 probe indicated the deletion of this region in two out of three copies of chromosome 17. The morphologic and immunophenotypic features, as well as the karyotypes observed in OvBH-1 in passages 135 and 385, were comparable. The monoclonality of the cell line was confirmed in a single cell cloning experiment. Our study indicated that OvBH-1 is characterized by a distinct karyotype and remains stable over 250 passages. Taking into account its thermosensitivity, its unusual karyotype, and its stability, this line can be considered as a valuable model for various experimental studies.

Establishment and partial characterization of five malignant glioma cell lines

Five malignant glioma cell lines (YMG1, 2, 3, 4, and 5) were established from surgical specimens obtained from patients with glioblastoma or anaplastic astrocytoma, and these lines were partially characterized. Three glioma cell lines (YMG1, 3, and 5) were weakly positive for GFAP by Western blot analysis and two cell lines were negative. S-100 protein was positive in all glioma cell lines. The expression of p53, p16, p15, cyclin-dependent kinase 4 (CDK4), and EGF receptor (EGFR) proteins was examined by Western blotting. YMG1 and 2 cell lines showed accumulation of p53 protein and loss of p16 and p15 expression. YMG3 and 4 showed accumulation of p53 protein and expression of p16 and p15 proteins. YMG5 revealed weak expression of p53 protein, suggesting wild-type p53, and loss of p16 and p15 expression. All cell lines expressed various levels of CDK4 protein. YMG1, 2, and 3 showed higher EGFR protein expression and YMG4 and 5 showed lower EGFR expression compared to U251 glioblastoma cells, which express high levels of EGFR. Fluorescence in situ hybridization analysis for EGFR gene expression did not show any amplification in the glioma cell lines. Immunohistochemical studies revealed that the patterns of p53 and EGFR expressions in the original tumor tissues were mostly correlated with those in the malignant glioma cell lines. These results suggest that the characteristics of p53 and EGFR expression in the malignant glioma cell lines were passed over from the original tumor tissues. These newly established malignant glioma cell lines can be used for further analysis of the mechanisms of tumor growth and progression.