Inhibition of Janus Kinase 1 synergizes docetaxel sensitivity in prostate cancer cells

Prostate cancer (PCa) is the second most common malignancy and is the fifth leading cause of cancer mortality among men globally. Docetaxel-based therapy remains the first-line treatment for metastatic castration-resistant prostate cancer. However, dose-limiting toxicity including neutropenia, myelosuppression and neurotoxicity is the major reason for docetaxel dose reductions and fewer cycles administered, despite a recent study showing a clear survival benefit with increased total number of docetaxel cycles in PCa patients. Although previous studies have attempted to improve the efficacy and reduce docetaxel toxicity through drug combination, no drug has yet demonstrated improved overall survival in clinical trial, highlighting the challenges of improving the activity of docetaxel monotherapy in PCa. Herein, we identified 15 lethality hits for which inhibition could enhance docetaxel sensitivity in PCa cells via a high-throughput kinome-wide loss-of-function screen. Further drug-gene interactions analyses identified Janus kinase 1 (JAK1) as a viable druggable target with existing experimental inhibitors and FDA-approved drugs. We demonstrated that depletion of endogenous JAK1 enhanced docetaxel-induced apoptosis in PCa cells. Furthermore, inhibition of JAK1/2 by baricitinib and ruxolitinib synergizes docetaxel sensitivity in both androgen receptor (AR)-negative DU145 and PC3 cells, but not in the AR-positive LNCaP cells. In contrast, no synergistic effects were observed in cells treated with JAK2-specific inhibitor, fedratinib, suggesting that the synergistic effects are mainly mediated through JAK1 inhibition. In conclusion, the combination therapy with JAK1 inhibitors and docetaxel could be a useful therapeutic strategy in the treatment of prostate cancers.

Gene expression profiling of giant fibroadenomas of the breast

INTRODUCTION

Fibroadenomas of the breast present as two phenotypic variants. The usual variety is 5 cm or less in diameter and there is another large variant called giant fibroadenoma which is greater than 5 cm in diameter. Despite of its large size, it is not malignant. The aim of our study is to determine whether this large variant is different from the usual fibroadenoma in terms of its biological pathways and biomarkers.

METHODS

mRNA was extracted from 44 fibroadenomas and 36 giant fibroadenomas, and transcriptomic profiling was performed to identify up- and down-regulated genes in the giant fibroadenomas as compared to the fibroadenomas.

RESULTS

A total of 40 genes were significantly up-regulated and 18 genes were significantly down-regulated in the giant fibroadenomas as compared to the fibroadenomas of the breast. The top 5 up-regulated genes were FN1, IL3, CDC6, FGF8 and BMP8A. The top 5 down-regulated genes were TNR, CDKN2A, COL5A1, THBS4 and BMPR1B. The differentially expressed genes (DEGs) were found to be associated with 5 major canonical pathways involved in cell growth (PI3K-AKT, cell cycle regulation, WNT, and RAS signalling) and immune response (JAK-STAT signalling). Further analyses using 3 supervised learning algorithms identified an 8-gene signature (FN1, CDC6, IL23A, CCNA1, MCM4, FLT1, FGF22 and COL5A1) that could distinguish giant fibroadenomas from fibroadenomas with high predictive accuracy.

CONCLUSION

Our findings demonstrated that the giant fibroadenomas are biologically distinct to fibroadenomas of the breast with overexpression of genes involved in the regulation of cell growth and immune response.

Parallel genome-wide RNAi screens identify lymphocyte-specific protein tyrosine kinase (LCK) as a targetable vulnerability of cell proliferation and chemoresistance in nasopharyngeal carcinoma

Despite recent in advances in the management of nasopharyngeal carcinoma (NPC), development of targeted therapy remains challenging particularly in patients with recurrent or metastatic disease. To search for clinically relevant targets for the treatment of NPC, we carried out parallel genome-wide functional screens to identified essential genes that are required for NPC cells proliferation and cisplatin resistance. We identified lymphocyte-specific protein tyrosine kinase (LCK) as a key vulnerability of both proliferation and cisplatin resistance. Depletion of endogenous LCK or treatment of cells with LCK inhibitor induced tumor-specific cell death and synergized cisplatin sensitivity in EBV-positive C666-1 and EBV-negative SUNE1 cells. Further analyses demonstrated that LCK is regulating the proliferation and cisplatin resistance through activation of signal transducer and activator of transcription 5 (STAT5). Taken together, our study provides a molecular basis for targeting LCK and STAT5 signaling as potential druggable targets for the management of NPC.

Roles of Inflammasomes in Epstein-Barr Virus-Associated Nasopharyngeal Cancer

Epstein-Barr virus (EBV) infection is recognised as one of the causative agents in most nasopharyngeal carcinoma (NPC) cases. Expression of EBV viral antigens can induce host's antiviral immune response by activating the inflammasomes to produce pro-inflammatory cytokines, such as interleukin-1β (IL-1β) and IL-18. These cytokines are known to be detrimental to a wide range of virus-infected cells, in which they can activate an inflammatory cell death program, called pyroptosis. However, aberrant inflammasome activation and production of its downstream cytokines lead to chronic inflammation that may contribute to various diseases, including NPC. In this review, we summarise the roles of inflammasomes during viral infection, how EBV evades inflammasome-mediated immune response, and progress into tumourigenesis. The contrasting roles of inflammasomes in cancer, as well as the current therapeutic approaches used in targeting inflammasomes, are also discussed in this review. While the inflammasomes appear to have dual roles in carcinogenesis, there are still many questions that remain unanswered. In particular, the exact molecular mechanism responsible for the regulation of the inflammasomes during carcinogenesis of EBV-associated NPC has not been explored thoroughly. Furthermore, the current practical application of inflammasome inhibitors is limited to specific tumour types, hence, further studies are warranted to discover the potential of targeting the inflammasomes for the treatment of NPC.

Sphingosine Kinase 1 Signaling in Breast Cancer: A Potential Target to Tackle Breast Cancer Stem Cells

Sphingosine kinases (SPHKs) are conserved lipid enzymes that catalyze the formation of sphingosine-1-phosphate (S1P) through ATP-dependent phosphorylation of sphingosine. Two distinct SPHK isoforms, namely SPHK1 and SPHK2, have been identified to date, and the former has been implicated for its oncogenic roles in cancer development and progression. While SPHK1 signaling axis has been extensively studied in non-stem breast cancer cells, recent evidence has emerged to suggest a role of SPHK1 in regulating cancer stem cells (CSCs). With the clinical implications of CSCs in disease relapse and metastasis, it is believed that therapeutic approaches that can eradicate both non-stem cancer cells and CSCs could be a key to cancer cure. In this review, we first explore the oncogenic functions of sphingosine kinase 1 in human cancers and summarize current research findings of SPHK1 signaling with a focus on breast cancer. We also discuss the therapeutic potentials and perspectives of targeting SPHK1 signaling in breast cancer and cancer stem cells. We aim to offer new insights and inspire future studies looking further into the regulatory functions of SPHK1 in CSC-driven tumorigenesis, uncovering novel therapeutic avenues of using SPHK1-targeted therapy in the treatment of CSC-enriched refractory cancers.

Phosphoinositide-dependent Kinase-1 (PDPK1) regulates serum/glucocorticoid-regulated Kinase 3 (SGK3) for prostate cancer cell survival

Prostate cancer (PCa) is the most common malignancy and is the second leading cause of cancer among men globally. Using a kinome-wide lentiviral small-hairpin RNA (shRNA) library screen, we identified phosphoinositide-dependent kinase-1 (PDPK1) as a potential mediator of cell survival in PCa cells. We showed that knock-down of endogenous human PDPK1 induced significant tumour-specific cell death in PCa cells (DU145 and PC3) but not in the normal prostate epithelial cells (RWPE-1). Further analyses revealed that PDPK1 mediates cancer cell survival predominantly via activation of serum/glucocorticoid-regulated kinase 3 (SGK3). Knock-down of endogenous PDPK1 in DU145 and PC3 cells significantly reduced SGK3 phosphorylation while ectopic expression of a constitutively active SGK3 completely abrogated the apoptosis induced by PDPK1. In contrast, no such effect was observed in SGK1 and AKT phosphorylation following PDPK1 knock-down. Importantly, PDPK1 inhibitors (GSK2334470 and BX-795) significantly reduced tumour-specific cell growth and synergized docetaxel sensitivity in PCa cells. In summary, our results demonstrated that PDPK1 mediates PCa cells' survival through SGK3 signalling and suggest that inactivation of this PDPK1-SGK3 axis may potentially serve as a novel therapeutic intervention for future treatment of PCa.

The Role of Ras-Associated Protein 1 (Rap1) in Cancer: Bad Actor or Good Player?

Metastasis is known as the most life-threatening event in cancer patients. In principle, the immune system can prevent tumor development. However, dysfunctional T cells may fail to eliminate the tumor cells effectively and provide additional survival advantages for tumor proliferation and metastasis. Constitutive activation of Ras-associated protein1 (Rap1) has not only led to T cell anergy, but also inhibited autophagy and supported cancer progression through various oncogenic events. Inhibition of Rap1 activity with its negative regulator, Rap1GAP, impairs tumor progression. However, active Rap1 reduces tumor invasion in some cancers, indicating that the pleiotropic effects of Rap1 signaling in cancers could be cancer-specific. All in all, targeting Rap1 signaling and its regulators could potentially control carcinogenesis, metastasis, chemoresistance and immune evasion. Rap1GAP could be a promising therapeutic target in combating cancer.

Molecular Mechanisms and Potential Therapeutic Reversal of Pancreatic Cancer-Induced Immune Evasion

Pancreatic cancer ranks high among the causes of cancer-related mortality. The prognosis of this grim condition has not improved significantly over the past 50 years, despite advancement in imaging techniques, cancer genetics and treatment modalities. Due to the relative difficulty in the early detection of pancreatic tumors, as low as 20% of patients are eligible for potentially curative surgery; moreover, chemotherapy and radiotherapy (RT) do not confer a great benefit in the overall survival of the patients. Currently, emerging developments in immunotherapy have yet to bring a significant clinical advantage among pancreatic cancer patients. In fact, pancreatic tumor-driven immune evasion possesses one of the greatest challenges leading to immunotherapeutic resistance. Most of the immune escape pathways are innate, while poor priming of hosts' immune response and immunoediting constitute the adaptive immunosuppressive machinery. In this review, we extensively discuss the pathway perturbations undermining the anti-tumor immunity specific to pancreatic cancer. We also explore feasible up-and-coming therapeutic strategies that may restore immunity and address therapeutic resistance, bringing hope to eliminate the status quo in pancreatic cancer prognosis.

Sphingosine Kinase 1 Regulates the Survival of Breast Cancer Stem Cells and Non-stem Breast Cancer Cells by Suppression of STAT1

Cancer stem cells (CSCs) represent rare tumor cell populations capable of self-renewal, differentiation, and tumor initiation and are highly resistant to chemotherapy and radiotherapy. Thus, therapeutic approaches that can effectively target CSCs and tumor cells could be the key to efficient tumor treatment. In this study, we explored the function of SPHK1 in breast CSCs and non-CSCs. We showed that RNAi-mediated knockdown of SPHK1 inhibited cell proliferation and induced apoptosis in both breast CSCs and non-CSCs, while ectopic expression of SPHK1 enhanced breast CSC survival and mammosphere forming efficiency. We identified STAT1 and IFN signaling as key regulatory targets of SPHK1 and demonstrated that an important mechanism by which SPHK1 promotes cancer cell survival is through the suppression of STAT1. We further demonstrated that SPHK1 inhibitors, FTY720 and PF543, synergized with doxorubicin in targeting both breast CSCs and non-CSCs. In conclusion, we provide important evidence that SPHK1 is a key regulator of cell survival and proliferation in breast CSCs and non-CSCs and is an attractive target for the design of future therapies.

Histone deacetylase (HDAC) inhibitors and doxorubicin combinations target both breast cancer stem cells and non-stem breast cancer cells simultaneously

PURPOSE

Breast cancer stem cells (CSCs) are a small subpopulation of cancer cells that have high capability for self-renewal, differentiation, and tumor initiation. CSCs are resistant to chemotherapy and radiotherapy, and are responsible for cancer recurrence and metastasis.

METHODS

By utilizing a panel of breast cancer cells and mammospheres culture as cell-based screening platforms, we performed high-throughput chemical library screens to identify agents that are effective against breast CSCs and non-CSCs. The hit molecules were paired with conventional chemotherapy to evaluate the combinatorial treatment effects on breast CSCs and non-CSCs.

RESULTS

We identified a total of 193 inhibitors that effectively targeting both breast CSCs and non-CSCs. We observed that histone deacetylase inhibitors (HDACi) synergized conventional chemotherapeutic agents (i.e., doxorubicin and cisplatin) in targeting breast CSCs and non-CSCs simultaneously. Further analyses revealed that quisinostat, a potent inhibitor for class I and II HDACs, potentiated doxorubicin-induced cytotoxicity in both breast CSCs and non-CSCs derived from the basal-like (MDA-MB-468 and HCC38), mesenchymal-like (MDA-MB-231), and luminal-like breast cancer (MCF-7). It was also observed that the basal-like breast CSCs and non-CSCs were more sensitive to the co-treatment of quisinostat with doxorubicin compared to that of the luminal-like breast cancer subtype.

CONCLUSION

In conclusion, this study demonstrates the potential of HDACi as therapeutic options, either as monotherapy or in combination with chemotherapeutics against refractory breast cancer.

The synergism of Clinacanthus nutans Lindau extracts with gemcitabine: downregulation of anti-apoptotic markers in squamous pancreatic ductal adenocarcinoma

BACKGROUND

Clinacanthus nutans extracts have been consumed by the cancer patients with the hope that the extracts can kill cancers more effectively than conventional chemotherapies. Our previous study reported its anti-inflammatory effects were caused by inhibiting Toll-like Receptor-4 (TLR-4) activation. However, we are unsure of its anticancer effect, and its interaction with existing chemotherapy.

METHODS

We investigated the anti-proliferative efficacy of polar leaf extracts (LP), non-polar leaf extracts (LN), polar stem extract (SP) and non-polar stem extracts (SN) in human breast, colorectal, lung, endometrial, nasopharyngeal, and pancreatic cancer cells using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, MTT assay. The most potent extracts was tested along with gemcitabine using our established drug combination analysis. The effect of the combinatory treatment in apoptosis were quantified using enzyme-linked immunosorbent assay (ELISA), Annexin V assay, antibody array and immunoblotting. Statistical significance was analysed using one-way analysis of variance (ANOVA) and post hoc Dunnett's test. A p-value of less than 0.05 (p < 0.05) was considered statistical significance.

RESULTS

All extracts tested were not able to induce potent anti-proliferative effects. However, it was found that pancreatic ductal adenocarcinoma, PDAC (AsPC1, BxPC3 and SW1990) were the cell lines most sensitive cell lines to SN extracts. This is the first report of C. nutans SN extracts acting in synergy with gemcitabine, the first line chemotherapy for pancreatic cancer, as compared to conventional monotherapy. In the presence of SN extracts, we can reduce the dose of gemcitabine 2.38-5.28 folds but still maintain the effects of gemcitabine in PDAC. SN extracts potentiated the killing of gemcitabine in PDAC by apoptosis. Bax was upregulated while bcl-2, cIAP-2, and XIAP levels were downregulated in SW1990 and BxPC3 cells treated with gemcitabine and SN extracts. The synergism was independent of TLR-4 expression in pancreatic cancer cells.

CONCLUSION

These results provide strong evidence of C. nutans extracts being inefficacious as monotherapy for cancer. Hence, it should not be used as a total substitution for any chemotherapy agents. However, SN extracts may synergise with gemcitabine in the anti-tumor mechanism.

Association of BRCA1- and BRCA2-deficiency with mutation burden, expression of PD-L1/PD-1, immune infiltrates, and T cell-inflamed signature in breast cancer

Immune checkpoint inhibitors have demonstrated effective anti-tumour response in cancer types with high mutation burden (e.g. melanoma) and in subset of cancers with features of genomic instability (e.g. mismatch-repair deficiency). One possible explanation for this effect is the increased expression of immune checkpoint molecules and pre-existing adaptive immune response in these cancers. Given that BRCA1 and BRCA2 are integral in maintaining genomic integrity, we hypothesise that the inactivation of these genes may give rise to breast cancers with such immunogenic phenotype. Therefore, using two large series of publicly available breast cancer datasets, namely that from The Cancer Genome Atlas and Wellcome Trust Institute, we sought to investigate the association between BRCA1- and BRCA2-deficiency with features of genomic instability, expression of PD-L1 and PD-1, landscape of inferred tumour-infiltrating immune cells, and T-cell inflamed signature in breast cancers. Here, we report that BRCA1 and BRCA2-deficient breast cancers were associated with features of genomic instability including increased mutation burden. Interestingly, BRCA1-, but not BRCA2-, deficient breast cancers were associated with increased expression of PD-L1 and PD-1, higher abundance of tumour-infiltrating immune cells, and enrichment of T cell-inflamed signature. The differences in immunophenotype between BRCA1- and BRCA2-deficient breast cancers can be attributed, in part, to PTEN gene mutation. Therefore, features of genomic instability such as that mediated by BRCA1- and BRCA2- deficiency in breast cancer were necessary, but not always sufficient, for yielding T cell-inflamed tumour microenvironment, and by extension, predicting clinical benefit from immunotherapy.

Therapeutic challenges and current immunomodulatory strategies in targeting the immunosuppressive pancreatic tumor microenvironment

BACKGROUND

Pancreatic cancer is one of the most lethal type of cancers, with an overall five-year survival rate of less than 5%. It is usually diagnosed at an advanced stage with limited therapeutic options. To date, no effective treatment options have demonstrated long-term benefits in advanced pancreatic cancer patients. Compared with other cancers, pancreatic cancer exhibits remarkable resistance to conventional therapy and possesses a highly immunosuppressive tumor microenvironment (TME).

MAIN BODY

In this review, we summarized the evidence and unique properties of TME in pancreatic cancer that may contribute to its resistance towards immunotherapies as well as strategies to overcome those barriers. We reviewed the current strategies and future perspectives of combination therapies that (1) promote T cell priming through tumor associated antigen presentation; (2) inhibit tumor immunosuppressive environment; and (3) break-down the desmoplastic barrier which improves tumor infiltrating lymphocytes entry into the TME.

CONCLUSIONS

It is imperative for clinicians and scientists to understand tumor immunology, identify novel biomarkers, and optimize the position of immunotherapy in therapeutic sequence, in order to improve pancreatic cancer clinical trial outcomes. Our collaborative efforts in targeting pancreatic TME will be the mainstay of achieving better clinical prognosis among pancreatic cancer patients. Ultimately, pancreatic cancer will be a treatable medical condition instead of a death sentence for a patient.

Identification of inhibitors synergizing gemcitabine sensitivity in the squamous subtype of pancreatic ductal adenocarcinoma (PDAC)

Pancreatic adenocarcinoma (PDAC) is a highly aggressive cancer with a high chance of recurrence, limited treatment options, and poor prognosis. A recent study has classified pancreatic cancers into four molecular subtypes: (1) squamous, (2) immunogenic, (3) pancreatic progenitor and (4) aberrantly differentiated endocrine exocrine. Among all the subtypes, the squamous subtype has the worst prognosis. This study aims to utilize large scale genomic datasets and computational systems biology to identify potential drugs targeting the squamous subtype of PDAC through combination therapy. Using the transcriptomic data available from the International Cancer Genome Consortium, Cancer Cell Line Encyclopedia and Connectivity Map, we identified 26 small molecules that could target the squamous subtype of PDAC. Among them include inhibitors targeting the SRC proto-oncogene (SRC) and the mitogen-activated protein kinase kinase 1/2 (MEK1/2). Further analyses demonstrated that the SRC inhibitors (dasatinib and PP2) and MEK1/2 inhibitor (pimasertib) synergized gemcitabine sensitivity specifically in the squamous subtype of PDAC cells (SW1990 and BxPC3), but not in the PDAC progenitor cells (AsPC1). Further analysis revealed that the synergistic effects are dependent on SRC or MEK1/2 activities, as overexpression of SRC or MEK1/2 completely abrogated the synergistic effects SRC inhibitors (dasatinib and PP2) and MEK1/2 inhibitor (pimasertib). In contrast, no significant toxicity was observed in the MRC5 human lung fibroblast and ARPE-19 human retinal pigment epithelial cells. Together, our findings suggest that combinations of SRC or MEK inhibitors with gemcitabine possess synergistic effects on the squamous subtype of PDAC cells and warrant further investigation.

Fibroblast growth factor receptor 4 (FGFR4) and fibroblast growth factor 19 (FGF19) autocrine enhance breast cancer cells survival

Basal-like breast cancer is an aggressive tumor subtype with poor prognosis. The discovery of underlying mechanisms mediating tumor cell survival, and the development of novel agents to target these pathways, is a priority for patients with basal-like breast cancer. From a functional screen to identify key drivers of basal-like breast cancer cell growth, we identified fibroblast growth factor receptor 4 (FGFR4) as a potential mediator of cell survival. We found that FGFR4 mediates cancer cell survival predominantly via activation of PI3K/AKT. Importantly, a subset of basal-like breast cancer cells also secrete fibroblast growth factor 19 (FGF19), a canonical ligand specific for FGFR4. siRNA-mediated silencing of FGF19 or neutralization of extracellular FGF19 by anti-FGF19 antibody (1A6) decreases AKT phosphorylation, suppresses cancer cell growth and enhances doxorubicin sensitivity only in the FGFR4⁺/FGF19⁺ breast cancer cells. Consistently, FGFR4/FGF19 co-expression was also observed in 82 out of 287 (28.6%) primary breast tumors, and their expression is strongly associated with AKT phosphorylation, Ki-67 staining, higher tumor stage and basal-like phenotype. In summary, our results demonstrated the presence of an FGFR4/FGF19 autocrine signaling that mediates the survival of a subset of basal-like breast cancer cells and suggest that inactivation of this autocrine loop may potentially serve as a novel therapeutic intervention for future treatment of breast cancers.

E-cadherin: Its dysregulation in carcinogenesis and clinical implications

E-cadherin is a transmembrane glycoprotein which connects epithelial cells together at adherens junctions. In normal cells, E-cadherin exerts its tumour suppressing role mainly by sequestering β-catenin from its binding to LEF (Lymphoid enhancer factor)/TCF (T cell factor) which serves the function of transcribing genes of the proliferative Wnt signaling pathway. Despite the ongoing debate on whether the loss of E-cadherin is the cause or effect of epithelial-mesenchymal transition (EMT), E-cadherin functional loss has frequently been associated with poor prognosis and survival in patients of various cancers. The dysregulation of E-cadherin expression that leads to carcinogenesis happens mostly at the epigenetic level but there are cases of genetic alterations as well. E-cadherin expression has been linked to the cellular functions of invasiveness reduction, growth inhibition, apoptosis, cell cycle arrest and differentiation. Studies on various cancers have shown that these different cellular functions are also interdependent. Recent studies have reported a rapid expansion of E-cadherin clinical relevance in various cancers. This review article summarises the multifaceted effect E-cadherin expression has on cellular functions in the context of carcinogenesis as well as its clinical implications in diagnosis, prognosis and therapeutics.

Jerantinine A induces tumor-specific cell death through modulation of splicing factor 3b subunit 1 (SF3B1)

Precursor mRNA (pre-mRNA) splicing is catalyzed by a large ribonucleoprotein complex known as the spliceosome. Numerous studies have indicated that aberrant splicing patterns or mutations in spliceosome components, including the splicing factor 3b subunit 1 (SF3B1), are associated with hallmark cancer phenotypes. This has led to the identification and development of small molecules with spliceosome-modulating activity as potential anticancer agents. Jerantinine A (JA) is a novel indole alkaloid which displays potent anti-proliferative activities against human cancer cell lines by inhibiting tubulin polymerization and inducing G2/M cell cycle arrest. Using a combined pooled-genome wide shRNA library screen and global proteomic profiling, we showed that JA targets the spliceosome by up-regulating SF3B1 and SF3B3 protein in breast cancer cells. Notably, JA induced significant tumor-specific cell death and a significant increase in unspliced pre-mRNAs. In contrast, depletion of endogenous SF3B1 abrogated the apoptotic effects, but not the G2/M cell cycle arrest induced by JA. Further analyses showed that JA stabilizes endogenous SF3B1 protein in breast cancer cells and induced dissociation of the protein from the nucleosome complex. Together, these results demonstrate that JA exerts its antitumor activity by targeting SF3B1 and SF3B3 in addition to its reported targeting of tubulin polymerization.

Cytochrome P450 2W1 (CYP2W1) in Colorectal Cancers

Cytochrome P450, family 2, subfamily W, polypeptide 1 (CYP2W1) is a newly identified monooxygenase enzyme that is expressed specifically in tumor tissues and during fetal life. Particularly, high expression of CYP2W1 was observed in up to 60% of colorectal cancers and its expression correlated with poor survival. CYP2W1 has been shown to metabolize various endogenous substrates including lysophospholipids and several procarcinogens, such as polycyclic aromatic hydrocarbon. The specific substrate for CYP2W1, however, is currently unknown. Due to its tumor-specific expression and its unique catalytic activities in colorectal cancers, CYP2W1 was deemed as an interesting target in colorectal cancer therapy. This review sought to summarize the current understanding of the CYP2W1 biology and biochemistry, its genetic polymorphisms and cancer risk, and its implication as a tumor-specific diagnostic and therapeutic target.

Functional roles of fibroblast growth factor receptors (FGFRs) signaling in human cancers

The fibroblast growth factor receptors (FGFRs) regulate important biological processes including cell proliferation and differentiation during development and tissue repair. Over the past decades, numerous pathological conditions and developmental syndromes have emerged as a consequence of deregulation in the FGFRs signaling network. This review aims to provide an overview of FGFR family, their complex signaling pathways in tumorigenesis, and the current development and application of therapeutics targeting the FGFRs signaling for treatment of refractory human cancers.

6-Shogaol inhibits breast and colon cancer cell proliferation through activation of peroxisomal proliferator activated receptor γ (PPARγ)

6-Shogaol has been shown to possess many antitumor properties including inhibition of cancer cell growth, inhibition of cancer metastasis, induction of apoptosis in cancer cells and induction of cancer cell differentiation. Despite its prominent antitumor effects, the direct molecular target of 6-shogaol has remained elusive. To identify the direct targets of 6-shogaol, a comprehensive antitumor profile of 6-shogaol (NSC752389) was tested in the NCI-60 cell line in an in vitro screen. The results show that 6-shogaol is COMPARE negative suggesting that it functions via a mechanism of action distinct from existing classes of therapeutic agents. Further analysis using microarray gene profiling and Connectivity Map analysis showed that MCF-7 cells treated with 6-shogaol display gene expression signatures characteristic of peroxisome proliferator activated receptor γ (PPARγ) agonists, suggesting that 6-shogaol may activate the PPARγ signaling pathway for its antitumor effects. Indeed, treatment of MCF-7 and HT29 cells with 6-shogaol induced PPARγ transcriptional activity, suppressed NFκB activity, and induced apoptosis in breast and colon cancer cells in a PPARγ-dependent manner. Furthermore, 6-shogaol is capable of binding to PPARγ with a binding affinity comparable to 15-delta prostaglandin J2, a natural ligand for PPARγ. Together, our findings suggest that the antitumor effects of 6-shogaol are mediated through activation of PPARγ and imply that activation of PPARγ might be beneficial for breast and colon cancer treatment.

Triple-negative breast cancer is associated with EGFR, CK5/6 and c-KIT expression in Malaysian women

BACKGROUND

Triple-negative breast cancer (TNBC) is a heterogeneous subgroup of breast cancer characterized by the lack of estrogen receptor (ER), progesterone receptor (PR) and the human epidermal growth factor receptor 2 (HER2) expressions. This subgroup of refractory disease tends to have aggressive clinical behavior, high frequency of metastasis and lack of response to current hormonal or targeted therapies. Despite numerous studies reporting the clinicopathological features of TNBC and its association with the basal-like phenotype in the Western population, only limited data are available in the Asian population. Therefore, the aim of this study was to investigate the clinicopathological characteristics of TNBC and its association with epidermal growth factor receptor (EGFR), cytokeratin 5/6 (CK5/6) and mast/stem cell growth factor receptor (c-KIT or CD117) expression in Malaysian women.

METHODS

A total of 340 patients diagnosed with primary breast cancer between 2002 and 2006 in Malaysia were reviewed and analyzed.

RESULTS

The incidence of TNBC was 12.4% (42/340). Bivariate analysis revealed that TNBC was strongly associated with a younger age, higher grade tumor and p53 expression. Further immunohistochemical analysis suggested that TNBC in Malaysian women was strongly associated with EGFR, CK5/6 and c-KIT expression with high a Ki-67 proliferation index.

CONCLUSION

In conclusion, our study confirms the association of TNBC with basal-like marker expression (EGFR, CK5/6 and c-KIT) in Malaysian women, consistent with studies in other populations.

Suppression of BCL-2 synergizes cisplatin sensitivity in nasopharyngeal carcinoma cells

The efficacy of cisplatin for treating nasopharyngeal carcinoma (NPC) is limited by the dose-related toxicities and the development of resistance to cisplatin. Recent studies have shown that B cell lymphoma-2 (BCL-2) is overexpressed and confers chemoresistance in NPC. Thus, targeted therapy against BCL-2 may enhance the antitumour effects of chemotherapy by sensitizing the tumor cells to undergo apoptosis. This study evaluated the combined effects of BCL-2 inhibition and cisplatin in NPC cells. Our results demonstrate that inhibition of BCL-2 by small-hairpin RNA (shRNA) or the BCL-2 inhibitor YC137, synergizes cisplatin sensitivity in NPC cells that overexpress BCL-2. We also show that YC137 enhance cisplatin-induced apoptosis in HK1 and CNE1 cells through suppression of BCL-2 protein expression, induction of mitochondrial depolarization and activation of caspase 9 and caspase 3/7. These findings suggest that the combination of BCL-2 inhibition and cisplatin represents a promising strategy for treating NPC.

CYP2S1 and CYP2W1 mediate 2-(3,4-dimethoxyphenyl)-5-fluorobenzothiazole (GW-610, NSC 721648) sensitivity in breast and colorectal cancer cells

Both 2-(4-amino-3-methylphenyl)-5-fluorobenzothiazole (5F-203; NSC 703786) and 2-(3,4-dimethoxyphenyl)-5-fluorobenzothiazole (GW-610; NSC 721648) are antitumor agents with novel mechanism(s). Previous studies have indicated that cytochrome (CYP) P450 1A1 is crucial for 5F-203 activity. In the present study, we investigated the functional role of 2 newly identified CYP P450 enzymes, CYP2S1 and CYP2W1, in mediating antitumor activity of benzothiazole compounds. We generated isogenic breast cancer (MDA-MB-468, MCF-7) and colorectal cancer (CRC; KM12 and HCC2998) cell lines depleted for CYP1A1, CYP2S1, or CYP2W1. The sensitivity of these cells to 5F-203 and GW-610 was then compared with vector control cells. 5F-203 exhibited potent activity against breast cancer cells, whereas GW-610 was effective against both breast and colorectal cancer cells. CYP1A1 was induced in both breast cancer and CRC cells, while CYP2S1 and CYP2W1 were selectively induced in breast cancer cells only following treatment with 5F-203 or GW-610. Depletion of CYP1A1 abrogated the sensitivity of breast cancer and CRC cells to 5F-203 and GW-610. Although depletion of CYP2S1 sensitized both breast cancer and CRC cells toward 5F-203 and GW-610, CYP2W1 knockdown caused marked resistance to GW-610 in CRC cells. Our results indicate that CYP-P450 isoforms, with the exception of CYP1A1, play an important role in mediating benzothiazole activity. CYP2S1 appears to be involved in deactivation of benzothiazoles, whereas CYP2W1 is important for bioactivation of GW-610 in CRC cells. Because CYP2W1 is highly expressed in colorectal tumors, GW-610 represents a promising agent for CRC therapy.

Mutant p53 mediates survival of breast cancer cells

Background:

p53 is the most commonly mutated tumour-suppressor gene in human cancers. Unlike other tumour-suppressor genes, most p53 cancer mutations are missense mutations within the core domain, leading to the expression of a full-length mutant p53 protein. Accumulating evidence has indicated that p53 cancer mutants not only lose tumour suppression activity but also gain new oncogenic activities to promote tumourigenesis.

Methods:

The endogenous mutant p53 function in human breast cancer cells was studied using RNA interference (RNAi). Gene knockdown was confirmed by quantitative PCR and western blotting. Apoptosis was evaluated by morphological changes of cells, their PARP cleavage and annexin V staining.

Results:

We show that cancer-associated p53 missense mutants are required for the survival of breast cancer cells. Inhibition of endogenous mutant p53 by RNAi led to massive apoptosis in two mutant p53-expressing cell lines, T47D and MDA-MB-468, but not in the wild-type p53-expressing cells, MCF-7 and MCF-10A. Reconstitution of an RNAi-insensitive mutant p53 in MDA-MB-468 cells completely abolished the apoptotic effects after silencing of endogenous mutant p53, suggesting the specific survival effects of mutant p53. The apoptotic effect induced by mutant p53 ablation, however, is independent of p63 or p73 function.

Conclusion:

These findings provide clear evidence of a pro-survival ‘gain-of-function’ property of a subset of p53 cancer mutants in breast cancer cells.