Increased expression of T-plastin gene in cisplatin-resistant human cancer cells: identification by mRNA differential display

The intricate mechanism of PLS3 in bone homeostasis and disease

Since our discovery in 2013 that genetic defects in PLS3 lead to bone fragility, the mechanistic details of this process have remained obscure. It has been established that PLS3 variants cause syndromic and nonsyndromic osteoporosis as well as osteoarthritis. PLS3 codes for an actin-bundling protein with a broad pattern of expression. As such, it is puzzling how PLS3 specifically leads to bone-related disease presentation. Our review aims to summarize the current state of knowledge regarding the function of PLS3 in the predominant cell types in the bone tissue, the osteocytes, osteoblasts and osteoclasts. This is related to the role of PLS3 in regulating mechanotransduction, calcium regulation, vesicle trafficking, cell differentiation and mineralization as part of the complex bone pathology presented by PLS3 defects. Considering the consequences of PLS3 defects on multiple aspects of bone tissue metabolism, our review motivates the study of its mechanism in bone diseases which can potentially help in the design of suitable therapy.

Proteomic Analysis of the Non-genetic Response to Cisplatin in Lung Cancer Cells

BACKGROUND

Drug resistance is the main cause of therapy failure in advanced lung cancer. Although non-genetic mechanisms play important roles in tumor chemoresistance, drug-induced epigenetic reprogramming is still poorly understood.

MATERIALS AND METHODS

The A549 cell line was used to generate cells with non-genetic resistance to cisplatin (CDDP), namely A549/CDDP cells. Bioorthogonal non-canonical amino acid tagging (BONCAT) and mass spectrometry were used to identify proteins modulated by CDDP in A549 and A549/CDDP cells.

RESULTS

Proteins related to proteostasis, telomere maintenance, cell adhesion, cytoskeletal remodeling, and cell redox homeostasis were found enriched in both cell lines upon CDDP exposure. On the other hand, proteins involved in drug response, metabolic pathways and mRNA processing and splicing were up-regulated by CDDP only in A549/CDDP cells.

CONCLUSION

Our study revealed proteome dynamics involved in the non-genetic response to CDDP, pointing out potential targets to monitor and overcome epigenetic resistance in lung cancer.

Plastin 3 in health and disease: a matter of balance

For a long time, PLS3 (plastin 3, also known as T-plastin or fimbrin) has been considered a rather inconspicuous protein, involved in F-actin-binding and -bundling. However, in recent years, a plethora of discoveries have turned PLS3 into a highly interesting protein involved in many cellular processes, signaling pathways, and diseases. PLS3 is localized on the X-chromosome, but shows sex-specific, inter-individual and tissue-specific expression variability pointing towards skewed X-inactivation. PLS3 is expressed in all solid tissues but usually not in hematopoietic cells. When escaping X-inactivation, PLS3 triggers a plethora of different types of cancers. Elevated PLS3 levels are considered a prognostic biomarker for cancer and refractory response to therapies. When it is knocked out or mutated in humans and mice, it causes osteoporosis with bone fractures; it is the only protein involved in actin dynamics responsible for osteoporosis. Instead, when PLS3 is upregulated, it acts as a highly protective SMN-independent modifier in spinal muscular atrophy (SMA). Here, it seems to counteract reduced F-actin levels by restoring impaired endocytosis and disturbed calcium homeostasis caused by reduced SMN levels. In contrast, an upregulation of PLS3 on wild-type level might cause osteoarthritis. This emphasizes that the amount of PLS3 in our cells must be precisely balanced; both too much and too little can be detrimental. Actin-dynamics, regulated by PLS3 among others, are crucial in a lot of cellular processes including endocytosis, cell migration, axonal growth, neurotransmission, translation, and others. Also, PLS3 levels influence the infection with different bacteria, mycosis, and other pathogens.

Plastin 3 in X-Linked Osteoporosis: Imbalance of Ca2+-Dependent Regulation Is Equivalent to Protein Loss

Osteogenesis imperfecta is a genetic disorder disrupting bone development and remodeling. The primary causes of osteogenesis imperfecta are pathogenic variants of collagen and collagen processing genes. However, recently variants of the actin bundling protein plastin 3 have been identified as another source of osteogenesis imperfecta. Plastin 3 is a highly conserved protein involved in several important cellular structures and processes and is controlled by intracellular Ca²⁺ which potently inhibits its actin-bundling activity. The precise mechanisms by which plastin 3 causes osteogenesis imperfecta remain unclear, but recent advances have contributed to our understanding of bone development and the actin cytoskeleton. Here, we review the link between plastin 3 and osteogenesis imperfecta highlighting in vitro studies and emphasizing the importance of Ca²⁺ regulation in the localization and functionality of plastin 3.

PLS3 predicts poor prognosis in pancreatic cancer and promotes cancer cell proliferation via PI3K/AKT signaling

Plastin-3 plays a key role in cancer cell proliferation and invasion, but its prognostic value in pancreatic cancer (PACA) remains poorly defined. In this study, we show that PLS3 messenger RNA is overexpressed in PACA tissue compared with normal tissue. We accumulated 207 cases of PACA specimens to perform immunohistochemical analysis and demonstrated that PLS3 levels correlate with T-classification (p < .001) and pathology (p < .001). Furthermore, overall survival rates (p < .001) in tumors with high PLS3 expression were poor, as assessed through Kaplan-Meier survival analysis. PLS3 was found to be an independent prognostic factor for PACA through multivariate Cox regression analysis. Moreover, we found that PLS3 enhances the proliferation and invasion of tumor cells as assessed through Cell Counting Kit-8, wounding healing assays, and Transwell assays. The upregulation of PLS3 also led to enhanced phosphatidylinositol-3 kinase/protein kinase B signaling in PACA cells. These data suggest that PLS3 is a biomarker to estimate PACA progression and represents a molecular target for PACA therapy.

Drug uptake-based chemoresistance in breast cancer treatment

Breast cancer is the most prevalent type of tumor and the second leading cause of death due to cancer among women. Although screening methods, diagnosis and therapeutic options have improved in the last decade, chemoresistance remains an important challenge. There is evidence relating breast cancer resistance with signaling pathways involving hormone and growth receptors, survival, apoptosis and the activation of efflux pumps. However, the resistance mechanisms linked to drug uptake are poorly understood, despite it often being observed that the drug content is lower in resistant cancer cells and that the entry of the drug into these cells is a limiting process for the subsequent therapeutic effect.In this review, we provide an overview of drug uptake-based resistance mechanisms developed by cancer cells in the four main types of chemotherapy used in breast cancer: anthracyclines, taxanes, oxazaphosphorines and platinum-based drugs. The contribution of tumor microenvironment to reduced drug-uptake and multidrug resistance is also analyzed. As a developing field, nanomedicine-based approaches provide promising opportunities to improve drug specific targeting, cell interaction and uptake into cancer cells. The endocytic-mediated pathways attributed to the different types of nanoformulations as well as the contribution of nanotherapeutics to overcoming chemoresistance affecting drug uptake in breast cancer will be described. New approaches focusing on drug uptake mechanisms could improve breast cancer chemotherapy, obtaining better dose-response outcomes and reducing toxic side effects.

The Actin Binding Protein Plastin-3 Is Involved in the Pathogenesis of Acute Myeloid Leukemia

Leukemia-initiating cells reside within the bone marrow in specialized niches where they undergo complex interactions with their surrounding stromal cells. We have identified the actin-binding protein Plastin-3 (PLS3) as potential player within the leukemic bone marrow niche and investigated its functional role in acute myeloid leukemia. High expression of PLS3 was associated with a poor overall and event-free survival for AML patients. These findings were supported by functional in vitro and in vivo experiments. AML cells with a PLS3 knockdown showed significantly reduced colony numbers in vitro while the PLS3 overexpression variants resulted in significantly enhanced colony numbers compared to their respective controls. Furthermore, the survival of NSG mice transplanted with the PLS3 knockdown cells showed a significantly prolonged survival in comparison to mice transplanted with the control AML cells. Further studies should focus on the underlying leukemia-promoting mechanisms and investigate PLS3 as therapeutic target.

Plastin 3 down-regulation augments the sensitivity of MDA-MB-231 cells to paclitaxel via the p38 MAPK signalling pathway

Plastin 3 (PLS3) overexpression may serve as a marker for predicting chemotherapeutic outcomes in drug-resistant cancer cells, but the mechanism is unclear. Herein, we show that the down-regulation of PLS3 by PLS3 gene silencing augments the sensitivity of MDA-MB-231 triple-negative breast cancer cells to paclitaxel. Interestingly, a low concentration of paclitaxel was able to induce strong apoptosis in the PLS3-silenced cells. Further study revealed that p38 MAPK signalling was responsible for the increased sensitivity to paclitaxel in these cells, as the p38 MAPK inhibitor SB203580 impaired the changes mediated by PLS3 down-regulation in response to paclitaxel. Therefore, our study identifies PLS3 as a potential target for enhancing the p38 MAPK-mediated apoptosis induced by paclitaxel. Unlike paclitaxel, Abraxane was unable to induce strong apoptosis in the PLS3-silenced cells. As PLS3 was found to be involved in the process of endocytosis in breast cancer cells, the reliance of cellular Abraxane uptake on this process may render it not as efficient as paclitaxel in PLS3-depleted tumour cells. The finding that PLS3 could be a critical regulator of paclitaxel sensitivity may have important implications for breast cancer chemotherapy.

Plastin 3 Expression Does Not Modify Spinal Muscular Atrophy Severity in the ∆7 SMA Mouse

Spinal muscular atrophy is caused by loss of the SMN1 gene and retention of SMN2. The SMN2 copy number inversely correlates with phenotypic severity and is a modifier of disease outcome. The SMN2 gene essentially differs from SMN1 by a single nucleotide in exon 7 that modulates the incorporation of exon 7 into the final SMN transcript. The majority of the SMN2 transcripts lack exon 7 and this leads to a SMN protein that does not effectively oligomerize and is rapidly degraded. However the SMN2 gene does produce some full-length SMN and the SMN2 copy number along with how much full-length SMN the SMN2 gene makes correlates with severity of the SMA phenotype. However there are a number of discordant SMA siblings that have identical haplotypes and SMN2 copy number yet one has a milder form of SMA. It has been suggested that Plastin3 (PLS3) acts as a sex specific phenotypic modifier where increased expression of PLS3 modifies the SMA phenotype in females. To test the effect of PLS3 overexpression we have over expressed full-length PLS3 in SMA mice. To ensure no disruption of functionality or post-translational processing of PLS3 we did not place a tag on the protein. PLS3 protein was expressed under the Prion promoter as we have shown previously that SMN expression under this promoter can rescue SMA mice. High levels of PLS3 mRNA were expressed in motor neurons along with an increased level of PLS3 protein in total spinal cord, yet there was no significant beneficial effect on the phenotype of SMA mice. Specifically, neither survival nor the fundamental electrophysiological aspects of the neuromuscular junction were improved upon overexpression of PLS3 in neurons.

Arsenite-induced changes in hepatic protein abundance in cynomolgus monkeys (Macaca fascicularis)

Arsenic is an environmental pollutant, and its liver toxicity has long been recognized. The effect of arsenic on liver protein expression was analyzed using a proteomic approach in monkeys. Monkeys were orally administered sodium arsenite (SA) for 28 days. As shown by 2D-PAGE in combination with MS, the expression levels of 16 proteins were quantitatively changed in SA-treated monkey livers compared to control-treated monkey livers. Specifically, the levels of two proteins, mortalin and tubulin beta chain, were increased, and 14 were decreased, including plastin-3, cystathionine-beta-synthase, selenium-binding protein 1, annexin A6, alpha-enolase, phosphoenolpyruvate carboxykinase-M, erlin-2, and arginase-1. In view of their functional roles, differential expression of these proteins may contribute to arsenic-induced liver toxicity, including cell death and carcinogenesis. Among the 16 identified proteins, four were selected for validation by Western blot and immunohistochemistry. Additional Western blot analyses indicated arsenic-induced dysregulation of oxidative stress related, genotoxicity-related, and glucose metabolism related proteins in livers from SA-treated animals. Many changes in the abundance of toxicity-related proteins were also demonstrated in SA-treated human hepatoma cells. These data on the arsenic-induced regulation of proteins with critical roles may help elucidate the specific mechanisms underlying arsenic-induced liver toxicity.

Aberrant expression of plastin-3 via copy number gain induces the epithelial-mesenchymal transition in circulating colorectal cancer cells

PURPOSE

Plastin-3 (PLS3) is a novel marker for circulating tumor cells (CTCs) in colorectal cancer (CRC). We sought to investigate the mechanisms mediating the aberrant expression of PLS3, the role of PLS3 in the epithelial-mesenchymal transition (EMT), and its association with the acquisition of invasive and metastatic abilities in human CRC.

METHODS

The expression levels of PLS3 messenger RNA in the tumor drainage venous blood (TDB) were examined in 177 CRC cases, and the associations between PLS3 expression and Xq23 copy numbers were analyzed in 132 CRC samples. We then established a stable PLS3-expressing CRC cell line and assessed the role of PLS3 in the EMT.

RESULTS

In clinical CRC cases, high expression of PLS3 in CTCs of TDB as well as peripheral blood was established as an independent prognostic factor of overall survival (p < 0.001), and the copy number gain of Xq23, which is the locus of the PLS3 gene, was significantly related to PLS3 overexpression. PLS3 induced the EMT via transforming growth factor (TGF)-β signaling and resulted in the acquisition of invasive ability in CRC cells.

CONCLUSIONS

The aberrant expression of PLS3 was associated with copy number gain in CTCs from primary tumors and was involved in the regulation of the EMT, contributing to a poor prognosis in CRC patients.

Plastin polymorphisms predict gender- and stage-specific colon cancer recurrence after adjuvant chemotherapy

Tumor recurrence after curative resection remains a major problem in patients with locally advanced colorectal cancer treated with adjuvant chemotherapy. Genetic single-nucleotide polymorphisms (SNP) may serve as useful molecular markers to predict clinical outcomes in these patients and identify targets for future drug development. Recent in vitro and in vivo studies have demonstrated that the plastin genes PLS3 and LCP1 are overexpressed in colon cancer cells and play an important role in tumor cell invasion, adhesion, and migration. Hence, we hypothesized that functional genetic variations of plastin may have direct effects on the progression and prognosis of locally advanced colorectal cancer. We tested whether functional tagging polymorphisms of PLS3 and LCP1 predict time to tumor recurrence (TTR) in 732 patients (training set, 234; validation set, 498) with stage II/III colorectal cancer. The PLS3 rs11342 and LCP1 rs4941543 polymorphisms were associated with a significantly increased risk for recurrence in the training set. PLS3 rs6643869 showed a consistent association with TTR in the training and validation set, when stratified by gender and tumor location. Female patients with the PLS3 rs6643869 AA genotype had the shortest median TTR compared with those with any G allele in the training set [1.7 vs. 9.4 years; HR, 2.84; 95% confidence interval (CI), 1.32-6.1; P = 0.005] and validation set (3.3 vs. 13.7 years; HR, 2.07; 95% CI, 1.09-3.91; P = 0.021). Our findings suggest that several SNPs of the PLS3 and LCP1 genes could serve as gender- and/or stage-specific molecular predictors of tumor recurrence in stage II/III patients with colorectal cancer as well as potential therapeutic targets.

A common gene variant in PLS3 predicts colon cancer recurrence in women

Recent evidence suggests that PLS3 (T-Plastin), an important member of the actin filamentous network, significantly influences cell invasion and metastasis. Germline polymorphisms within the PLS3 gene may impact the gene's function, resulting in inter-individual differences in tumor recurrence capacity. In the present study, we investigated the association of germline polymorphisms in PLS3 to predict time to recurrence (TTR) in patients with stage II and III colon cancer. A total of 264 patients with histologically confirmed colon cancer were included in this retrospective study. Germline DNA was genotyped for rs871773 C>T, rs757124 C>G, rs1557770 G>T, rs6643869 G>A, and rs2522188 C>T in the PLS3 gene by 5'-exonuclease (TaqMan™) technology. As the PLS3 gene is located on the X chromosome, a gender-specific statistical analysis was performed. In univariate analysis, the minor allele of PLS3 rs871773 C>T was significantly associated with decreased TTR in women (hazard ratio (HR) = 5.02; 95 % confidence interval (CI) = 1.251-20.114; p = 0.023) and remained significantly associated in multivariate analysis (HR = 6.165; 95 % CI = 1.538-24.716; p = 0.010). Female patients carrying the C/T genotype in PLS3 rs871773 showed a median TTR of 69 months. In contrast, female patients with homozygous C/C had a median TTR of 112 months. There were no significant associations between PLS3 rs871773 C>T and TTR in male and between the other polymorphisms and TTR in male or female colon cancer patients. In conclusion, we identified a common gene variant in PLS3 as an independent prognostic marker in female patients with stage II and III colon cancer. Larger prospective trials are warranted to confirm these findings.

Plastin3 is a novel marker for circulating tumor cells undergoing the epithelial-mesenchymal transition and is associated with colorectal cancer prognosis

Circulating tumor cells (CTC) in blood have attracted attention both as potential seeds for metastasis and as biomarkers. However, most CTC detection systems might miss epithelial-mesenchymal transition (EMT)-induced metastatic cells because detection is based on epithelial markers. First, to discover novel markers capable of detecting CTCs in which EMT has not been repressed, microarray analysis of 132 colorectal cancers (CRC) from Japanese patients was conducted, and 2,969 genes were detected that were overexpressed relative to normal colon mucosa. From the detected genes, we selected those that were overexpressed CRC with distant metastasis. Then, we analyzed the CRC metastasis-specific genes (n = 22) to determine whether they were expressed in normal circulation. As a result, PLS3 was discovered as a CTC marker that was expressed in metastatic CRC cells but not in normal circulation. Using fluorescent immunocytochemistry, we validated that PLS3 was expressed in EMT-induced CTC in peripheral blood from patients with CRC with distant metastasis. PLS3-expressing cells were detected in the peripheral blood of approximately one-third of an independent set of 711 Japanese patients with CRC. Multivariate analysis showed that PLS3-positive CTC was independently associated with prognosis in the training set (n = 381) and the validation set [n = 330; HR = 2.17; 95% confidence interval (CI) = 1.38-3.40 and HR = 3.92; 95% CI = 2.27-6.85]. The association between PLS3-positive CTC and prognosis was particularly strong in patients with Dukes B (HR = 4.07; 95% CI = 1.50-11.57) and Dukes C (HR = 2.57; 95% CI = 1.42-4.63). PLS3 is a novel marker for metastatic CRC cells, and it possesses significant prognostic value.

Inducible expression and pathophysiologic functions of T-plastin in cutaneous T-cell lymphoma

A molecular feature of Sézary syndrome (SS) is the abnormal expression of T-plastin by malignant T cells. Herein, we investigated the molecular mechanisms involved in T-plastin synthesis and the functions of this actin-binding protein, with a special interest in chemoresistance and migration. We confirm the specific expression of T-plastin in peripheral blood lymphocytes (PBLs) from SS patients and its total absence in PBLs from patients with mycosis fungoides, inflammatory cutaneous or hematologic diseases, and from healthy volunteers. Only 3 of 4 SS patients did constitutively express T-plastin. To assess whether T-plastin expression was inducible, T-plastin-negative PBLs were stimulated by phorbol 12-myristate 13-acetate and ionomycin. Our results demonstrate that T-plastin synthesis was induced in negative PBLs from SS patients, other studied patients, and healthy volunteers. Both constitutive and calcium-induced T-plastin expression was down-regulated by calcineurin inhibitors and involved nuclear factor of activated T cells transcription pathway. Constitutive T-plastin expression in SS was associated with resistance to etoposide-induced apoptosis and cell migration toward chemokines (TARC/CCL17, IP-10). In conclusion, T-plastin is a marker restricted to malignant lymphocytes from SS patients and plays a role for cell survival and migration. This opens new strategies for the treatment of SS advanced stages.

Regulation of T-plastin expression by promoter hypomethylation in primary cutaneous T-cell lymphoma

T-plastin (PLS3) is an actin-bundling protein normally expressed in epithelial cells but absent in cells of hematopoietic origin. Aberrant PLS3 expression has been demonstrated in lymphocytes from Sézary syndrome (SS) patients and has been proposed as a biomarker for SS; however, the mechanism underlying dysregulation of PLS3 has not been determined. In this study, PLS3 mRNA expression was demonstrated in 21/35 (60%) SS patients and in 3/8 (38%) mycosis fungoides patients, all of whom had clonal blood involvement. No evidence for PLS3 mutations within coding or promoter regions was found, but significant hypomethylation of CpG dinucleotides 95-99 within the PLS3 CpG island was observed and this was restricted to the PLS3+ population. A polyclonal antibody specific to PLS3 was raised to examine coexpression of PLS3 with a panel of T-cell differentiation markers. All PLS3+ cells were CD3+CD4+ and CD26-, suggesting that loss of CD26 is consistently associated with gain of PLS3, whereas all other markers were distributed heterogeneously. However, a patient-specific TCR copy number assay also demonstrated heterogeneity in PLS3 expression in tumor cell populations. Importantly, our findings demonstrate PLS3 expression in the majority of SS patients and provide insight into the molecular regulation of PLS3 expression in CTCL.

Proteomic profile regulated by the anticancer peptide CIGB-300 in non-small cell lung cancer (NSCLC) cells

CIGB-300 is a proapoptotic peptide-based drug that abrogates the CK2-mediated phosphorylation. This peptide has antineoplastic effect on lung cancer cells in vitro and in vivo. To understand the mechanisms involved on such anticancer activity, the NCI-H125 cell line proteomic profile after short-term incubation (45 min) with CIGB-300 was investigated. As determined by 2-DE or 2D-LC-MS/MS, 137 proteins changed their abundances more than 2-fold in response to the CIGB-300 treatment. The expression levels of proteins related to ribosome biogenesis, metastasis, cell survival and proliferation, apoptosis, and drug resistance were significantly modulated by the presence of CIGB-300. The protein translation process was the most affected (23% of the identified proteins). From the proteome analysis of the NCI-H125 cell line, novel potentialities for CIGB-300 as anticancer agent were evidenced.

Enhanced S100 calcium-binding protein P expression sensitizes human bladder cancer cells to cisplatin

OBJECTIVE

• To investigate the role of S100 calcium-binding protein P (S100P) in the gain of cis-diamminedichloroplatinum (II) (cisplatin) resistance in bladder cancer, having previously found, with cDNA microarrays using two pairs of parental (T24, KK47) and their cisplatin-resistant bladder cancer cell lines (T24/DDP10, KK47/DDP20), that S100P mRNA expression was significantly reduced in cisplatin-resistant cells.

MATERIALS AND METHODS

• S100P mRNA and protein expression levels were investigated by northern and western blot analyses, respectively. • Intracellular S100P localization was examined by immunocytochemistry and immunohistochemistry. • S100P over-expression, obtained by transfection with S100P expression plasmid, was used to investigate whether or not S100P affected cellular resistance to cisplatin.

RESULTS

• S100P mRNA showed increased expression by cisplatin stimulation in parental cell lines. • On the other hand, S100P mRNA and protein expression levels were markedly reduced in cisplatin-resistant cells. • The over-expression of S100P in resistant cells resulted in an increased sensitivity to cisplatin.

CONCLUSIONS

• In bladder cancer cells, S100P was expressed and localized mainly in the nucleus. • S100P expression was also involved in cisplatin sensitivity. • S100P might thus represent a molecular marker predicting cisplatin sensitivity and a molecular therapeutic target for cisplatin-based chemotherapy.

Gene expression profiles as biomarkers for the prediction of chemotherapy drug response in human tumour cells

Genome profiling approaches such as cDNA microarray analysis and quantitative reverse transcription polymerase chain reaction are playing ever-increasing roles in the classification of human cancers and in the discovery of biomarkers for the prediction of prognosis in cancer patients. Increasing research efforts are also being directed at identifying set of genes whose expression can be correlated with response to specific drugs or drug combinations. Such genes hold the prospect of tailoring chemotherapy regimens to the individual patient, based on tumour or host gene expression profiles. This review outlines recent advances and challenges in using genome profiling for the identification of tumour or host genes whose expression correlates with response to chemotherapy drugs both in vitro and in clinical studies. Genetic predictors of response to a variety of anticancer agents are discussed, including the anthracyclines, taxanes, topoisomerase I and II inhibitors, nucleoside analogs, alkylating agents, and vinca alkaloids.

Characterisation of two rat mammary tumour models for breast cancer research by gene expression profiling

Breast cancer is the most frequently occurring cancer in women. Treatment options are still an active area of research. Models used for this purpose include induced models in rodents. By the advent of microarrays it has become possible to evaluate models not only for similar morphology or selected markers by polymerase chain reaction (PCR) or immunohistochemistry but also for the expression of thousands of genes at once. This study presents gene expression profiles of the hormone-sensitive 7,12-dimethylbenzanthracene-induced and the metastasising MTLn3-model. The models are discussed for their relevance to breast cancer in humans.

The inflammatory and normal transcriptome of mouse bladder detrusor and mucosa

Background

An organ such as the bladder consists of complex, interacting set of tissues and cells. Inflammation has been implicated in every major disease of the bladder, including cancer, interstitial cystitis, and infection. However, scanty is the information about individual detrusor and urothelium transcriptomes in response to inflammation. Here, we used suppression subtractive hybridizations (SSH) to determine bladder tissue- and disease-specific genes and transcriptional regulatory elements (TRE)s. Unique TREs and genes were assembled into putative networks.

Results

It was found that the control bladder mucosa presented regulatory elements driving genes such as myosin light chain phosphatase and calponin 1 that influence the smooth muscle phenotype. In the control detrusor network the Pax-3 TRE was significantly over-represented. During development, the Pax-3 transcription factor (TF) maintains progenitor cells in an undifferentiated state whereas, during inflammation, Pax-3 was suppressed and genes involved in neuronal development (synapsin I) were up-regulated. Therefore, during inflammation, an increased maturation of neural progenitor cells in the muscle may underlie detrusor instability. NF-κB was specifically over-represented in the inflamed mucosa regulatory network. When the inflamed detrusor was compared to control, two major pathways were found, one encoding synapsin I, a neuron-specific phosphoprotein, and the other an important apoptotic protein, siva. In response to LPS-induced inflammation, the liver X receptor was over-represented in both mucosa and detrusor regulatory networks confirming a role for this nuclear receptor in LPS-induced gene expression.

Conclusion

A new approach for understanding bladder muscle-urothelium interaction was developed by assembling SSH, real time PCR, and TRE analysis results into regulatory networks. Interestingly, some of the TREs and their downstream transcripts originally involved in organogenesis and oncogenesis were also activated during inflammation. The latter represents an additional link between inflammation and cancer. The regulatory networks represent key targets for development of novel drugs targeting bladder diseases.

Molecular basis for dissimilar nuclear trafficking of the actin-bundling protein isoforms T- and L-plastin

T- and L-plastin are highly similar actin-bundling proteins implicated in the regulation of cell morphology, lamellipodium protrusion, bacterial invasion and tumor progression. We show that T-plastin localizes predominantly to the cytoplasm, whereas L-plastin distributes between nucleus and cytoplasm in HeLa or Cos cells. T-plastin shows nuclear accumulation upon incubation of cells with the CRM1 antagonist leptomycin B (LMB). We identified a Rev-like nuclear export sequence (NES) in T-plastin that is able to export an otherwise nuclear protein in an LMB-dependent manner. Deletion of the NES promotes nuclear accumulation of T-plastin. Mutation of residues L17, F21 or L26 in the T-plastin NES inhibits nuclear efflux. L-plastin harbors a less conserved NES and lacks the F21 T-plastin residue. Insertion of a Phe residue in the L-plastin NES specifically enhances its export activity. These findings explain why both isoforms exhibit specific distribution patterns in eukaryotic cells.

Plastins: versatile modulators of actin organization in (patho)physiological cellular processes

Many actin-binding proteins are expressed in eukaryotic cells. These polypeptides assist in stabilizing and rearranging the organization of the actin cytoskeleton in response to external stimuli, or during cell migration and adhesion. Here we review a particular set of actin-binding proteins called plastins. Plastins (also called fimbrins) belong to a subclass of actin-binding proteins known as actin bundling proteins. Three isoforms have been characterized in mammals: T-plastin is expressed in cells from solid tissue, whereas L-plastin occurs predominantly in hematopoietic cells. The third isoform, I-plastin, is specifically expressed in the small intestine, colon and kidney. These proteins share the unique property of cross-linking actin filaments into tight bundles. Although plastins are primarily involved in regulation of the actin cytoskeleton, they possess some unique features. For instance, they are implicated in invasion by pathogenic bacteria such as Shigella flexneri and Salmonella typhimurium. Also, L-plastin plays an important role in leukocyte function. T-plastin, on the other hand, is possibly involved in DNA repair. Finally, both T- and L-plastin are implicated in several diseases, and L-plastin is considered to be a valuable marker for cancer.

Inositol 1,4,5-trisphosphate (IP3) receptor type1 (IP3R1) modulates the acquisition of cisplatin resistance in bladder cancer cell lines

To investigate the molecules that regulate the acquisition of cis-diamminedichloroplatinum (II) (cisplatin) resistance, we performed cDNA microarrays using two pairs of parental and cisplatin-resistant bladder cancer cell lines. We found a markedly reduced expression of inositol 1,4,5-trisphosphate (IP3) receptor type1 (IP3R1), endoplasmic reticulum membrane protein, in cisplatin-resistant cells. The suppression of IP3R1 expression using small interfering RNA in parental cells prevented apoptosis and resulted in decreased sensitivity to cisplatin. Contrarily, overexpression of IP3R1 in resistant cells induced apoptosis and increased sensitivity to cisplatin. These results suggest that cisplatin-induced downregulation of IP3R1 expression was closely associated with the acquisition of cisplatin resistance in bladder cancer cells.

Changes in T-plastin expression with human trophoblast differentiation

During the first trimester of pregnancy, the human placenta is an actively dividing and highly invasive tumour-like tissue, while near term, it represents a fully developed, non-invasive unit. In order to understand the molecular basis of this marked difference in the placental phenotypes, an approach based on a differential display-reverse transcription-polymerase chain reaction (DD-RT-PCR) was adopted to analyse changes in gene expression, using total RNA isolated from first-trimester and term placental villi. Using this approach, T-plastin was initially identified as being differentially expressed in the human first-trimester placenta. T-plastin is an actin-bundling protein and is known to be highly expressed in actively dividing cells and up-regulated in several carcinomas. Using a homogenous population of cytotrophoblasts and syncytiotrophoblasts isolated from human placentae, the present authors demonstrate the differential expression of T-plastin in cytotrophoblasts compared with the terminally differentiated syncytiotrophoblasts. The down-regulation of T-plastin expression is further demonstrated in human trophoblastic BeWo cells induced to differentiate using transforming growth factor (TGF)beta1, a growth factor known for its anti-proliferative and anti-invasive response in placental cells. These studies suggest that expression of T-plastin in the placental context may indeed be associated with the enhanced replicative potential of placental trophoblasts.

Proteome analysis of vinca alkaloid response and resistance in acute lymphoblastic leukemia reveals novel cytoskeletal alterations

Vinca alkaloids are used widely in the treatment of both childhood and adult cancers. Their cellular target is the beta-tubulin subunit of alpha/beta-tubulin heterodimers, and they act to inhibit cell division by disrupting microtubule dynamics. Despite the effectiveness of these agents, drug resistance is a major clinical problem. To identify the underlying mechanisms behind vinca alkaloid resistance, we have performed high resolution differential proteome analysis. Treatment of drug-sensitive human leukemia cells (CCRF-CEM) with vincristine identified numerous proteins involved in the cellular response to vincristine. In addition, differential protein expression was analyzed in leukemia cell lines selected for resistance to vincristine (CEM/VCR R) and vinblastine (CEM/VLB100). This combined proteomic approach identified 10 proteins altered in both vinca alkaloid response and resistance: beta-tubulin, alpha-tubulin, actin, heat shock protein 90beta, 14-3-3tau, 14-3-3epsilon, L-plastin, lamin B1, heterogeneous nuclear ribonuclear protein-F, and heterogeneous nuclear ribonuclear protein-K. Several of these proteins have not previously been associated with drug resistance and are thus novel targets for elucidation of resistance mechanisms. In addition, seven of these proteins are associated with the tubulin and/or actin cytoskeletons. This study provides novel insights into the interrelationship between the microtubule and microfilament systems in vinca alkaloid resistance.

Differentially expressed genes associated with CIS-diamminedichloroplatinum (II) resistance in head and neck cancer using differential display and CDNA microarray

BACKGROUND

The mechanism by which cancer cells become resistant to cis-Diamminedichloroplatinum (II) (cDDP) is not completely understood. To investigate the molecular markers involved in the cDDP resistance, we compared the gene expression profiles between a head and neck squamous cell carcinoma (HNSCC) line sensitive to cDDP and its cDDP-resistant variant.

METHODS

Both a fluorescent differential display and a cDNA microarray analysis were applied to distinguish the gene profiles between KB, a human HNSCC line, and its cDDP-resistant variant (KB/cDDP). These results were confirmed by Northern blot analysis.

RESULTS

One up-regulated gene, glycoprotein hormone alpha-subunit, and two down-regulated genes coding membrane proteins, human folate receptor and tumor-associated antigen L6, were identified in KB/cDDP cells.

CONCLUSIONS

Our findings suggest that development of the cDDP-resistant phenotype is accompanied by alternations of gene expression including a glycoprotein hormone and membrane proteins. These gene products could be new molecular markers for resistance to cDDP.

Increased expression of T-fimbrin gene after DNA damage in CHO cells and inactivation of T-fimbrin by CpG methylation in human colorectal cancer cells

When DNA damage is induced by unprogrammed extrinsic events, activating-cell-cycle checkpoints delay cell-cycle progression in the G1 or G2 phases and allow repair of a damaged template. In this study, we evaluated changes in gene expression upon radiation-induced G2 cell-cycle arrest using Chinese hamster ovary (CHO) cells. T-fimbrin, an actin-binding protein, was overexpressed in CHO cells in which G2 arrest had been induced by X-radiation. Northern blot analysis revealed that T-fimbrin gene expression was induced not only by X-radiation but also by a topoisomerase II inhibitor, etoposide. Transfection of CHO cells with a vector encoding T-fimbrin antisense RNA demonstrated that reduced T-fimbrin expression induced alterations in cell-cycle control; radiation-induced G2 arrest was short and decreased in cells transfected with antisense T-fimbrin. Additionally, T-fimbrin gene expression was suppressed in a human colorectal cancer cell line, SW948, because of promoter-specific DNA methylation. These results suggest that downregulation of T-fimbrin may be involved in cancer development through G2/M cell-cycle control in mammalian cells.

Differential display analysis of breast carcinoma cells enriched by immunomagnetic target cell selection: gene expression profiles in bone marrow target cells

The red bone marrow (BM) is an important indicator organ of hematogenous micrometastatic spread of carcinomas. Characterization of biological properties specific for BM micrometastatic cells, however, is technically challenging due to the limited number of target cells usually available for the purpose. This report provides referrals to qualitative gene expression profiling of BM micrometastatic cells enriched by immunomagnetic selection. First, an experimental strategy was used to study regulatory mechanisms involved when BM micrometastatic cells colonize distant organs. The MA-11 cells, originating from BM micrometastases in a breast cancer patient clinically devoid of overt metastatic disease, were injected into immunodeficient rats. Metastatic MA-11 cells were subsequently immunoselected from the resulting in vivo lesions. The selected cell populations were compared to the injected cells by differential display analysis, and several genes possibly involved in tumor cell invasion and proliferation were confirmed as differentially expressed among the various MA-11 cell populations. A direct approach to qualitative gene expression profiling of BM micrometastatic cells was also explored. Carcinoma cells were immunoselected from BM and axillary lymph nodes obtained from breast cancer patients, and the isolated cell populations were compared by differential display analysis. Two candidate genes, identified as factors involved in cellular growth control, appeared as differentially expressed by the target cells from BM. Our study provides detailed information on how to combine an immunomagnetic selection procedure and differential display analysis to reveal gene expression profiles that may characterize BM micrometastatic cells.

Discovering functional relationships between RNA expression and chemotherapeutic susceptibility using relevance networks

In an effort to find gene regulatory networks and clusters of genes that affect cancer susceptibility to anticancer agents, we joined a database with baseline expression levels of 7,245 genes measured by using microarrays in 60 cancer cell lines, to a database with the amounts of 5,084 anticancer agents needed to inhibit growth of those same cell lines. Comprehensive pair-wise correlations were calculated between gene expression and measures of agent susceptibility. Associations weaker than a threshold strength were removed, leaving networks of highly correlated genes and agents called relevance networks. Hypotheses for potential single-gene determinants of anticancer agent susceptibility were constructed. The effect of random chance in the large number of calculations performed was empirically determined by repeated random permutation testing; only associations stronger than those seen in multiply permuted data were used in clustering. We discuss the advantages of this methodology over alternative approaches, such as phylogenetic-type tree clustering and self-organizing maps.

cDNA Technologies and their application to drug resistance research: power, potential and problems

The effectiveness of systemic chemotherapy is dramatically limited by both intrinsic and acquired drug resistance. Several new technologies have been developed over the last decade to more rapidly identify underlying genetic alterations that impart a drug-resistant phenotype. Techniques such as cDNA-based subtraction technologies, SAGE analysis, and most recently cDNA array and high-density micro-array technologies have rapidly expanded our ability to detect changes in RNA transcription in drug-resistant tumors. These technologies are currently being applied to generate a large number of new hypotheses regarding the regulatory molecules underlying the drug-resistance phenotype. These techniques suggest that there is a large number of transcriptional changes which occur in the drug-resistance phenotype and future work will need to focus on dissecting which of these transcriptional changes are central to the drug resistance phenotype, both in vitro, and more importantly within clinical neoplasia. Copyright 2000 Harcourt Publishers Ltd.

CROP/Luc7A, a novel serine/arginine-rich nuclear protein, isolated from cisplatin-resistant cell line

A novel putative SR protein, designated cisplatin resistance-associated overexpressed protein (CROP), has been cloned from cisplatin-resistant cell lines by differential display. The N-half of the deduced amino acid sequence of 432 amino acids of CROP contains cysteine/histidine motifs and leucine zipper-like repeats. The C-half consists mostly of charged and polar amino acids: arginine (58 residues or 25%), glutamate (36 residues or 16%), serine (35 residues or 15%), lysine (30 residues, 13%), and aspartate (20 residues or 9%). The C-half is extremely hydrophilic and comprises domains rich in lysine and glutamate residues, rich in alternating arginine and glutamate residues, and rich in arginine and serine residues. The arginine/serine-rich domain is dominated by a series of 8 amino acid imperfect repetitive motif (consensus sequence, Ser-Arg-Ser-Arg-Asp/Glu-Arg-Arg-Arg), which has been found in RNA splicing factors. The RNase protection assay and Western blotting analysis indicate that the expression of CROP is about 2-3-fold higher in mRNA and protein levels in cisplatin-resistant ACHN/CDDP cells than in host ACHN cells. CROP is the human homologue of yeast Luc7p, which is supposed to be involved in 5'-splice site recognition and is essential for vegetative growth.

Structural characterization of the human interleukin-13 receptor alpha1 gene promoter

Human cancer cells have been found to express a large number of IL-13 receptors. We have previously shown that mRNA encoding one of these receptors, IL-13Ralpha1, is increased in cisplatin-resistant cells and is upregulated in tumor cells cultured with cisplatin. To understand the molecular mechanism of IL-13Ralpha1 gene expression, we cloned approximately 52 kbp of the IL-13Ralpha1 gene and sequenced the first exon and about 1 kbp of the upstream DNA. The first exon is 211 bp and contains 88 bp of coding sequence, while the first intron is about 13 kbp in length. The promoter region, which is GC rich, was found to lack both TATA and CCAAT boxes. Transient expression assays revealed that transcription of the IL-13Ralpha1 gene was significantly higher in cisplatin-resistant cells than in parental, cisplatin-sensitive cells. Deletion analysis of the IL-13Ralpha1 promoter identified a 70-bp core promoter region upstream of the transcription initiation site. Electrophoretic gel mobility shift assays showed that a synthetic IL-13Ralpha1 oligonucleotide (nt -40 to nt -15) bound a nuclear factor from cisplatin-resistant cells to a significantly greater degree than the equivalent factor from parental cells. This oligonucleotide was found to contain a palindromic sequence with a BstEII recognition site at its center. This palindromic sequence functions to mediate upregulation of IL-13Ralpha1 promoter in cisplatin-resistant cells and deletion or disruption of this sequence also resulted in severe reduction of the promoter activity. These findings suggest that IL-13Ralpha1 expression is upregulated at the transcriptional level in cisplatin-resistant cells. The characterization of both the IL-13Ralpha1 promoter and the transcription factors binding to it may contribute to our understanding of IL-13Ralpha1 regulation in cancer cells.

EB-1, a tyrosine kinase signal transduction gene, is transcriptionally activated in the t(1;19) subset of pre-B ALL, which express oncoprotein E2a-Pbx1

The t(1;19) translocation of pre-B cell acute lymphocytic leukemia (ALL) produces E2a-Pbx1, a chimeric oncoprotein containing the transactivation domains of E2a joined to the homeodomain protein, Pbx1. E2a-Pbx1 causes T cell and myeloid leukemia in mice, blocks differentiation of cultured myeloid progenitors, and transforms fibroblasts through a mechanism accompanied by aberrant expression of tissue-specific and developmentally-regulated genes. Here we investigate whether aberrant gene expression also occurs specifically in the t(1;19)-containing subset of pre-B cell ALL in man. Two new genes, EB-1 and EB-2, as well as Caldesmon were transcriptionally activated in each of seven t(1;19) cell lines. EB-1 expression was extremely low in marrow from patients having pre-B ALL not associated with the t(1;19), and elevated more than 100-fold in marrow from patients with pre-B ALL associated with the t(1;19). Normal EB-1 expression was strong in brain and testis, the same tissues exhibiting the highest levels of PBX1 expression. EB-1 encodes a signaling protein containing a phosphotyrosine binding domain homologous to that of dNumb developmental regulators and two SAM domains homologous to those in the C-terminal tail of Eph receptor tyrosine kinases. We conclude that aberrant expression of tissue-specific genes is a characteristic of t(1;19) pre-B ALL, as was previously found in fibroblasts transformed by E2a-Pbx1. Potentially, EB-1 overexpression could interfere with normal signaling controlling proliferation or differentiation.

Mechanisms of drug resistance in chemotherapy for urogenital carcinoma

Cancer chemotherapy is the principal approach for urogenital cancers. However, the acquisition of resistance to anticancer agents is a critical factor that limits the successful treatment of malignancies. The multidrug resistant (MDR) phenotype has been widely recognized in cancer chemotherapy in urogenital tumors and the mechanisms underlying MDR have also been extensively studied. One of the principle mechanisms in MDR is caused by the overexpression of P-glycoprotein (P-gp), encoded by the multidrug resistance gene (MDR1). It functions as an ATP-dependent active efflux pump of chemotherapeutic agents in human cancer cells. Recently, other drug resistance proteins, including multidrug resistance-associated protein (MRP1) and cMOAT (or MRP2), were also identified from multidrug resistant cells. A functional analysis of MRP1 has shown that MRP1 may have the potential to act as a transporter of glutathione conjugates, which has been known as a central detoxification pathway in anticancer agents. Furthermore, several other resistance-related proteins (e.g. glutathione S-transferase, metallothionein, thioredoxin, topoisomerase I, II, O6-alkylguanine-DNA methyltransferase, etc.) have been found to be up- or down-regulated in resistant cells and these molecules are believed to contribute to the resistant phenotype as well. Based on the molecular characteristics identified in MDR, several experimental and clinical approaches have been studied to overcome MDR. One of these strategies is to reverse MDR by using such P-gp inhibitors as verapamil and cyclosporine A. In this review, we summarize the recent advances in MDR-related molecules and clinical trials to circumvent MDR in urogenital carcinomas.

An invasion-associated Salmonella protein modulates the actin-bundling activity of plastin

The entry of Salmonella typhimurium into nonphagocytic cells requires a panel of bacterial effector proteins that are delivered to the host cell via a type III secretion system. These proteins modulate host-cell signal-transduction pathways and the actin cytoskeleton to induce membrane ruffling and bacterial internalization. One of these bacterial effectors, termed SipA, is an actin-binding protein that is required for efficient Salmonella entry into host cells. We report here that SipA forms a complex with T-plastin on bacterial infection. Formation of such a complex, which requires the presence of F-actin, results in a marked increase in the actin-bundling activity of T-plastin. We also report that T-plastin is recruited to S. typhimurium-induced membrane ruffles by a CDC42-dependent signaling process and is required for bacterial entry. We propose that modulation of the actin-bundling activity of T-plastin by SipA results in the stabilization of the actin filaments at the point of bacterial-host cell contact, which leads to more efficient Salmonella internalization.

Genomic imbalances associated with acquired resistance to platinum analogues

During the past several years, a panel of human tumor cell lines (predominantly ovarian) with acquired resistance to cisplatin, the orally bioavailable analogue JM216, and the structurally hindered analogue AMD473, has been established and characterized for underlying mechanisms of resistance. We have examined these resistant cell lines for gains and losses of DNA associated with the acquisition of resistance using the molecular cytogenetic technique of comparative genomic hybridization. Our comparison of three analogues has shown the most frequently observed changes to include amplification of 4q (5/7) and 6q (5/7), followed by amplification of 5q (3/7). We have defined four minimal common overrepresented regions, two each on 4q and 6q, which are potential loci of genes associated with platinum analogue resistance. Additional consistent abnormalities appear to be associated with cell lines sharing specific resistance mechanisms. For example, amplification of 12q was observed in the CH1 lines made respectively resistant to JM216 and AMD473 in which increased DNA repair appears to be a major mechanism of resistance for both agents. Hence, these comparative genomic hybridization studies have identified distinct chromosomal aberrations which may correlate with defined mechanisms of resistance and contain hitherto unrecognized genes that may provide targets for future therapeutic intervention.

Search for genes involved in UV-resistance in human cells by mRNA differential display: increased transcriptional expression of nucleophosmin and T-plastin genes in association with the resistance

UVr-10 UV-resistant cells were established from UV-sensitive human RSb cells. We searched here for genes expressed differentially between UVr-10 and RSb cells using a differential display method to elucidate the molecular mechanisms underlying the UV-resistance. Thirteen candidate cDNA fragments were obtained from 514 mRNA species first screened. Among the cDNA fragments, 3 revealed increased mRNA expression in UVr-10 cells compared with RSb cells by Northern analysis. Nucleotide sequence analysis identified 2 of the 3 cDNA fragments as encoding nucleophosmin (NPM) and T-plastin. The expression of NPM mRNA was induced after UV irradiation in UVr-10 cells but not in RSb cells, whereas irradiation did not affect the expression of T-plastin mRNA. UVr-10 cells transfected with antisense cDNA for NPM mRNA were partially sensitized to UV cell-killing. Thus, NPM and possibly T-plastin genes may contribute to the increased resistance to UV cell-killing, at least in the human cells tested.

Strategies for whole microbial genome sequencing and analysis

The introduction of methods for automated DNA sequence analysis nearly a decade ago, together with more recent advances in the field of bioinformatics, have revolutionized biology and medicine and have ushered in a new era of genomic science, the study of genes and genomes. These new technologies have had an impact on many areas of research, including the association between genes and disease, in DNA-based diagnostics, and in the sequencing of genomes from human and other model organisms. The demonstration in 1995, that automated DNA sequencing methods could be used to decipher the entire genome sequence of a free-living organism, Haemophilus influenzae, was a milestone in both the genomics and microbial fields [1]. Since the first report of the complete sequence of H. influenzae, these methodologies have been adopted by laboratories around the world. The complete genomic sequence of five eubacterial species [1-5], one archaea [6], and the eukaryote, Saccharomyces cerevisiae [7], have been reported in the last 18 months. At the beginning of 1997 more than a dozen microbial genome projects are at or near completion, with many others in progress. It is likely that in the next few years we will see the complete sequence of perhaps as many as 30-40 microbial genomes. In this article, we will review methods for whole genome sequencing and analysis and examine how this information can be exploited to better understand microbial physiology and evolution.