Expression of cyclin D1a and D1b as predictive factors for treatment response in colorectal cancer

Aberrant Cyclin D1 splicing in cancer: from molecular mechanism to therapeutic modulation

Cyclin D1 (CCND1), a crucial mediator of cell cycle progression, possesses many mutation types with different mutation frequencies in human cancers. The G870A mutation is the most common mutation in CCND1, which produces two isoforms: full-length CCND1a and divergent C-terminal CCND1b. The dysregulation of the CCND1 isoforms is associated with multiple human cancers. Exploring the molecular mechanism of CCND1 isoforms has offer new insight for cancer treatment. On this basis, the alterations of CCND1 gene are described, including amplification, overexpression, and mutation, especially the G870A mutation. Subsequently, we review the characteristics of CCND1 isoforms caused by G870A mutation. Additionally, we summarize cis-regulatory elements, trans-acting factors, and the splice mutation involved in splicing regulation of CCND1. Furthermore, we highlight the function of CCND1 isoforms in cell cycle, invasion, and metastasis in cancers. Importantly, the clinical role of CCND1 isoforms is also discussed, particularly concerning prognosis, chemotherapy, and radiotherapy. Last, emphasis is given to the corrective strategies that modulate the cancerous CCND1 isoforms. Thus, it is highlighting significance of aberrant isoforms of CCND1 as targets for cancer therapy.

Voacamine is a novel inhibitor of EGFR exerting oncogenic activity against colorectal cancer through the mitochondrial pathway

Colorectal cancer (CRC), among the most aggressive and prevailing neoplasms, is primarily treated with chemotherapy. Voacamine (VOA), a novel bisindole natural product, possesses a variety of conspicuous pharmacological activities. Within the current research, we evaluated in vitro and in vivo the anticancer efficacy of VOA against CRC and its potential mechanisms. Our results illustrated that VOA concentrationdependently suppressed the proliferation and migration of CT26 and HCT116 cells as correspondingly indicated by IC₅₀ values of 1.38 ± 0.09 μM and 4.10 ± 0.14 μM. Furthermore, treatment of VOA also suppressed tumor cell colony formation, escalated the late-stage apoptosis rate of tumor cells, and evoked cell cycle of CT26 and HCT116 cells arrest inhibition in G2-M and G0-G1 phases, respectively. Meanwhile, VOA markedly disrupted the mitochondrial membrane potential eliciting mitochondrial dysfunction, decreased ATP production, and intermediated an enhanced accumulation of intracellular reactive oxygen species with a concentration-dependent pattern, accompanied by elevated expression levels of pro-apoptotic related protein Bax, Cyt-C, cleaved caspases 3/8/9 and by diminished Bcl-2, Bid, PRAP and caspases 3/8/9 expression. Further mechanistic studies revealed VOA treatment suppressed the EGFR/PI3K/Akt pathway with the evidence of the decreased phosphorylation proteins of EGFR, PI3K, Akt, and downstream proteins of p-mTOR, p-NF-kB, and p-P70S6. Additionally, molecular dynamics simulations further displayed VOA could enter the EGFR pocket followed by multiple mutual interaction effects. Interestingly, the EGFR activator (NSC228155) could slack the inhibitory capability of VOA on the EGFR/PI3K/Akt pathway as well as VOA-induced impairment of mitochondrial function. Finally, administration of VOA (15, 30 mg/kg every 2 days, i.p., for 16 days) in CT26 syngeneic mice dose-dependently suppressed the neoplastic development without appreciable organ toxicities. Taken together, our study demonstrated that VOA may be a prospective therapeutic agent for the treatment of CRC.

Histone methyltransferase SETDB1 promotes colorectal cancer proliferation through the STAT1-CCND1/CDK6 axis

Upregulation of histone methyltransferase SET domain bifurcated 1 (SETDB1) is associated with poor prognosis in cancer patients. However, the mechanism of oncogenicity of SETDB1 in cancer is hitherto unknown. Here, we show that SETDB1 is upregulated in human colorectal cancer (CRC) where its level correlates with poor clinical outcome. Ectopic SETDB1 promotes CRC cell proliferation, whereas SETDB1 attenuation inhibits this process. Flow cytometry reveals that SETDB1 promotes proliferation by driving the CRC cell cycle from G0/G1 phase to S phase. Mechanistically, SETDB1 binds directly to the STAT1 promoter region resulting in increased STAT1 expression. Functional characterization reveals that STAT1-CCND1/CDK6 axis is a downstream effector of SETDB1-mediated CRC cell proliferation. Furthermore, SETDB1 upregulation is sufficient to accelerate in vivo proliferation in xenograft animal model. Taken together, our results provide insight into the upregulation of SETDB1 within CRC and can lead to novel treatment strategies targeting this cell proliferation-promoting gene.

Prognostic Significance of Cyclin D1 Over-expression in Colorectal Cancer: An Experience from Madinah, Saudi Arabia

Background and study aim: Cyclin D1 is a key regulatory protein in the cell cycle and is over-expressed in many tumors, including endometrial, thyroid, urothelial, breast, brain gliomas, and esophageal cancers. The main aim of the present study is to examine the expression pattern of cyclin D1 and its correlation with the different clinicopathological features in patients with colorectal camcer (CRC) from the Madinah region of Saudi Arabia. Patients and methods: The archival tumor blocks were analyzed using immunohistochemistry for Cyclin D1 over-expression in 324 CRC patients diagnosed from January 2006 to December 2017, at the Department of Pathology, King Fahad Hospital, Madinah, Saudi Arabia. Results: Cyclin D1 over-expression was absent in normal mucosa, while 15% cases of adenoma showed its over-expression. In CRC, Cyclin D1 was expressed at high levels in 24.1% of case. No significant correlation was observed between Cyclin D1 over-expression and age, gender, tumor size, type and location. However, Cyclin D1 over-expression exhibited a significant correlation with tumor differentiation (p=0.04), lymph node involvement (p=0.001), lymphovascular invasion (p=0.001), distant metastasis (p=0.006) and AJCC staging (p=0.001). The Kaplan-Meir analysis revealed a shorter period of survival with Cyclin D1 over-expression (p=0.000). The Cox-regression model analysis showed that Cyclin D1 over-expression was an independent prognostic marker in CRC (p=0.000). Conclusion: Cyclin D1 over-expression increases during normal-adenoma-carcinoma sequence. The significant association observed between Cyclin D1 over-expression, advanced tumor stage and short survival period clearly suggest the role of Cyclin D1 in the carcinogenesis and progression of CRC.

A network-based predictive gene-expression signature for adjuvant chemotherapy benefit in stage II colorectal cancer

Background

The clinical benefit of adjuvant chemotherapy for stage II colorectal cancer (CRC) is controversial. This study aimed to explore novel gene signature to predict outcome benefit of postoperative 5-Fu-based therapy in stage II CRC.

Methods

Gene-expression profiles of stage II CRCs from two datasets with 5-Fu-based adjuvant chemotherapy (training dataset, n = 212; validation dataset, n = 85) were analyzed to identify the indicator. A systemic approach by integrating gene-expression and protein-protein interaction (PPI) network was implemented to develop the predictive signature. Kaplan-Meier curves and Cox proportional hazards model were used to determine the survival benefit of adjuvant chemotherapy. Experiments with shRNA knock-down were carried out to confirm the signature identified in this study.

Results

In the training dataset, we identified 44 PPI sub-modules, by which we separate patients into two clusters (1 and 2) having different chemotherapeutic benefit. A predictor of 11 PPI sub-modules (11-PPI-Mod) was established to discriminate the two sub-groups, with an overall accuracy of 90.1%. This signature was independently validated in an external validation dataset. Kaplan-Meier curves showed an improved outcome for patients who received adjuvant chemotherapy in Cluster 1 sub-group, but even worse survival for those in Cluster 2 sub-group. Similar results were found in both the training and the validation dataset. Multivariate Cox regression revealed an interaction effect between 11-PPI-Mod signature and adjuvant therapy treatment in the training dataset (RFS, p = 0.007; OS, p = 0.006) and the validation dataset (RFS, p = 0.002). From the signature, we found that PTGES gene was up-regulated in CRC cells which were more resistant to 5-Fu. Knock-down of PTGES indicated a growth inhibition and up-regulation of apoptotic markers induced by 5-Fu in CRC cells.

Conclusions

Only a small proportion of stage II CRC patients could benefit from adjuvant therapy. The 11-PPI-Mod as a potential predictor could be helpful to distinguish this sub-group with favorable outcome.

Electronic supplementary material

The online version of this article (10.1186/s12885-017-3821-4) contains supplementary material, which is available to authorized users.

LGR5 and CD133 as prognostic and predictive markers for fluoropyrimidine-based adjuvant chemotherapy in colorectal cancer

BACKGROUND

Expression of leucine-rich-repeat-containing G-protein-coupled receptor 5 (LGR5) gene is associated with a metastatic phenotype and poor prognosis in colorectal cancer (CRC). CD133 expression is a putative cancer stem cell marker and a proposed prognostic marker in CRC, whereas the predictive value of CD133 expression for effect of adjuvant chemotherapy in CRC is unclear.

MATERIAL AND METHODS

For the study of LGR5 mRNA and CD133 expression, tissue microarrays from 409 primary CRC stage II and III tumors, where patients had been randomized to adjuvant chemotherapy or surgery only, were available. LGR5 mRNA and CD133 expression were assessed by in situ hybridization (ISH) and immunohistochemistry (IHC), respectively. LGR5 mRNA and CD133 expression as prognostic and predictive markers were evaluated by univariate and multivariate analyses.

RESULTS

For all CRC patients, positive LGR5 mRNA and CD133 expression were associated with classic adenocarcinoma histology type (p = 0.001 and p = 0.014, respectively). Positive LGR5 mRNA expression was also associated with smaller tumor diameter for CRC stage II (p = 0.005), but not for CRC stage III (p = 0.054). For CRC stage II, lack of LGR5 mRNA expression was associated with longer time to recurrence (TTR) in Kaplan-Meier (p = 0.045) and in multivariate Cox analysis (HR 0.27, 95% CI 0.08-0.95, p = 0.041). For colon cancer stage III patients, lack of CD133 expression was associated with better effect of adjuvant chemotherapy (p = 0.016) in Kaplan-Meier univariate analysis, but the interaction between CD133 and adjuvant chemotherapy was not statistically significant in multivariate analysis (HR 0.59, 95% CI 0.18-1.89, p = 0.374).

CONCLUSION

LGR5 mRNA expression is a prognostic factor for CRC stage II patients, whereas the value of CD133 expression as prognostic and predictive biomarker is inconclusive.

Human epidermal growth factor receptor 4 (Her4) Suppresses p53 Protein via Targeting the MDMX-MDM2 Protein Complex: IMPLICATION OF A NOVEL MDMX SER-314 PHOSPHOSITE

Deregulated receptor tyrosine kinase (RTK) signaling is frequently associated with tumorigenesis and therapy resistance, but its underlying mechanisms still need to be elucidated. In this study, we have shown that the RTK human epidermal growth factor receptor 4 (Her4, also known as Erbb4) can inhibit the tumor suppressor p53 by regulating MDMX-mouse double minute 2 homolog (MDM2) complex stability. Upon activation by either overexpression of a constitutively active vector or ligand binding (Neuregulin-1), Her4 was able to stabilize the MDMX-MDM2 complex, resulting in suppression of p53 transcriptional activity, as shown by p53-responsive element-driven luciferase assay and mRNA levels of p53 target genes. Using a phospho-proteomics approach, we functionally identified a novel Her4-induced posttranslational modification on MDMX at Ser-314, a putative phosphorylation site for the CDK4/6 kinase. Remarkably, inhibition of Ser-314 phosphorylation either with Ser-to-Ala substitution or with a specific inhibitor of CDK4/6 kinase blocked Her4-induced stabilization of MDMX-MDM2 and rescued p53 activity. Our study offers insights into the mechanisms of deregulated RTK-induced carcinogenesis and provides the basis for the use of inhibitors targeting RTK-mediated signals for p53 restoration.

Association of Mixed Lineage Kinase Domain-Like Protein Expression With Prognosis in Patients With Colon Cancer

BACKGROUND

The mixed lineage kinase domain-like protein has recently been identified as a key downstream component of tumor necrosis factor-induced necroptosis, which is an important pathway of cancer cell death. The goal of the current study is to explore the expression of mixed lineage kinase domain-like protein in colon cancer tissues and evaluate the prognostic value in patients with colon cancer.

METHODS

We collected normal and cancer colon tissues from 135 patients diagnosed with colon cancer after radical operation during July 2007 to April 2009 at The Affiliated Hospital of Qingdao University. Immunohistochemistry analysis was scored using an established scoring system. Kaplan-Meier survival curves were generated for recurrence-free survival and overall survival for all patients and 2 subsets of patients. The relationship between mixed lineage kinase domain-like protein expression and prognosis parameter (recurrence-free survival, overall survival) was analyzed by univariate and multivariate Cox regression analyses.

RESULTS

The median age of all patients was 67 years and 56.3% were male. Low expression of mixed lineage kinase domain-like protein was associated with decreased overall survival (78.6 vs 81.2 months; P = .011) in all patients. In the subset of 79 patients who received adjuvant chemotherapy, low expression of mixed lineage kinase domain-like protein was associated with decreased recurrence-free survival (60.4 vs 72.8 months; P = .032) and decreased overall survival (66.3 vs 72.9 months; P = .005). Low expression of mixed lineage kinase domain-like protein was associated with decreased overall survival (74.9 vs 79.8 months; P = .006) and recurrence-free survival (69.6 vs 78.8 months; P = .005) among patients with Tumor Node Metastasis (TNM) stage II colon cancer.

CONCLUSIONS

Low expression of mixed lineage kinase domain-like protein was associated with decreased overall survival in all patient-group with resected colon cancer. It is associated with decreased recurrence-free survival and overall survival in the subset of patients who receive adjuvant chemotherapy and patients who were TNM stage II. Mixed lineage kinase domain-like protein may provide important prognostic information in patients with colon cancer.

Hepatic injury is associated with cell cycle arrest and apoptosis with alteration of cyclin A and D1 in ammonium chloride-induced hyperammonemic rats

Hyperammonemia is considered to be central to the pathophysiology of hepatic encephalopathy in patients exhibiting hepatic failure (HF). It has previously been determined that hyperammonemia is a serious metabolic disorder commonly observed in patients with HF. However, it is unclear whether hyperammonemia has a direct adverse effect on hepatic cells or serves as a cause and effect of HF. The present study investigated whether hepatic injury is caused by hyperammonemia, and aimed to provide an insight into the causes and mechanisms of HF. Hyperammonemic rats were established via intragastric administration of ammonium chloride solution. Hepatic tissues were assessed using biochemistry, histology, immunohistochemistry, flow cytometry (FCM), semi-quantitative reverse transcription-polymerase chain reaction and western blot analysis. Hyperammonemic rats exhibited significantly increased levels of liver function markers, including alanine transaminase (P<0.01), aspartate aminotransferase (P<0.01), blood ammonia (P<0.01) and direct bilirubin (P<0.05), which indicated hepatic injury. A pathological assessment revealed mild hydropic degeneration, but no necrosis or inflammatory cell infiltration. However, terminal deoxynucleotidyl transferase dUTP nick end-labeling assays confirmed a significant increase in the rate of cellular apoptosis in hyperammonemic rat livers (P<0.01). FCM analysis revealed that there were significantly more cells in the S phase and fewer in the G₂/M phase (P<0.01), and the expression levels of cyclin A and D1 mRNA and proteins were significantly increased (P<0.01). In summary, cell cycle arrest, apoptosis and an alteration of cyclin A and D1 levels were all markers of hyperammonemia-induced hepatic injury. These findings provide an insight into the potential mechanisms underlying hyperammonemia-induced hepatic injury, and may be used as potential targets for treating or preventing hepatic damage caused by hyperammonemia, including hepatic encephalopathy.

Enrichment of nuclear S100A4 during G2/M in colorectal cancer cells: possible association with cyclin B1 and centrosomes

S100A4 promotes metastasis in several types of cancer, but the involved molecular mechanisms are still incompletely described. The protein is associated with a wide variety of biological functions and it locates to different subcellular compartments, including nuclei, cytoplasm and extracellular space. Nuclear expression of S100A4 has been associated with more advanced disease stage as well as poor outcome in colorectal cancer (CRC). The present study was initiated to investigate the nuclear function of S100A4 and thereby unravel potential biological mechanisms linking nuclear expression to a more aggressive phenotype. CRC cell lines show heterogeneity in nuclear S100A4 expression and preliminary experiments revealed cells in G2/M to have increased nuclear accumulation compared to G1 and S cells, respectively. Synchronization experiments validated nuclear S100A4 expression to be most prominent in the G2/M phase, but manipulating nuclear levels of S100A4 using lentiviral modified cells failed to induce changes in cell cycle distribution and proliferation. Proximity ligation assay did, however, demonstrate proximity between S100A4 and cyclin B1 in vitro, while confocal microscopy showed S100A4 to localize to areas corresponding to centrosomes in mitotic cells prior to chromosome segregation. This might indicate a novel and uncharacterized function of the metastasis-associated protein in CRC cells.

Nuclear maspin expression as a predictive marker for fluorouracil treatment response in colon cancer

BACKGROUND

Maspin is a member of the serpin family of protease inhibitors whose function in colorectal cancer is not fully understood. The objective of this study was to determine whether level of maspin expression could have prognostic or predictive value in colorectal cancer.

MATERIAL AND METHODS

Maspin expression was assessed using immunohistochemistry on tissue microarrays obtained from 380 patients with stage II and III colorectal cancer randomized to adjuvant chemotherapy with fluorouracil and levamisole (5-FU/Lev) or to surgery only (control), with scores (0-300) based on presence (0-100) and intensity (0-3) of maspin expression. Associations with disease-free survival (DFS), cancer-specific survival (CSS) and prognostic factors were determined.

RESULTS

Maspin expression was predominantly nuclear and present in tumor tissue in 99% of the cases. No associations with clinicopathological factors were identified. In colon cancer patients receiving adjuvant chemotherapy, maspin expression level was significantly associated with CSS [HR 1.43 per 50 points increase in maspin score (p = 0.021)] in multivariate analyses, and a significant interaction between treatment status and maspin expression (p = 0.045) was found. Kaplan-Meier plots from colon cancer patients showed a significant treatment benefit in patients with low maspin expression, but not for individuals with medium/high expression. Level of maspin expression was not significantly related to clinical outcome in rectal cancer or in any of the control groups.

CONCLUSIONS

In patients with colon cancer a low nuclear maspin expression was an independent predictor of benefit from adjuvant chemotherapy with 5-FU/Lev. A prognostic value of maspin expression was not found in this material.

Immunoexpression of cyclin D1 in colorectal carcinomas is not correlated with survival outcome

Background

Colon and colorectal cancer (CRC) research has entered a new era with recent updates of molecular events and prognostic markers. Among other prognostic markers, exaggerated expression of nuclear CCND1 has key role in tumour pathogenesis and metastases of CRC and has also been claimed to predict response to treatment.

Objectives

This study was designed to evaluate the prognostic and predictive value of CCND1 in CRC and the correlation of CCND1 expression with the different clinicopathological parameters.

Methods

Paraffin blocks from 117 primary CRC were retrieved from the archives of the Department of Pathology at King Abdulaziz University. Tissue microarrays were designed and constructed. The immunostaining of CCND1 was performed and analysed.

Results

There were more cases with low nuclear immunoexpression of CCND1 in both primary tumours and nodal metastasis (p <0.001). Cyclin D1 did not show association with clinicopathological features except with lymphovascular invasion. Low nuclear immunoexpression of CCND1 was associated with negative lymphovascular invasion (p = 0.046). There was no statistically significant correlation between CCND1 immunoexpression and survival probability (Log Rank = 2.474, p = 0.116).

Conclusion

Our study indicates that CCND1 immunoexpression cannot be used as a predictor of survival in CRC. It also shows no significant correlation with clinicopathological features except with lymphovascular invasion.

Inhibition of STAT3/cyclinD1 pathway promotes chemotherapeutic sensitivity of colorectal caner

BACKGROUND

Chemotherapeutic resistance indicated the poor prognosis of colorectal cancer.

OBJECTIVE

Our study aimed to investigate the role of STAT3/cyclinD1 pathway in the chemotherapeutic resistance of colorectal cancer.

METHODS

We firstly measured the expression of cyclinD1 in the colorectal cancer tissues using immunohistochemistry in tissue microarray. Then cell viability and apoptosis were investigated in the HT-29 cell lines dealing with recombinant lentivirus and shRNA to increase or decrease cyclinD1 expression. Furthermore, luciferase and ChIP assays were applied to investigate whether STAT3 regulated cyclinD1 expression by binding to its promoter. Finally, we determined whether inhibition of STAT3 could decrease cyclinD1 and increase the chemotherapy sensitivity.

RESULTS

CyclinD1 expression was significantly increased in the cancer cells and high level of cyclinD1 indicated the poor prognosis. Inhibition of cyclinD1 decreased the cell viability assessed by MTT and increased rate of apoptosis when exposed to 5-FU treatment while overexpression of cyclinD1 showed the reverse effect. ChIP assay showed that STAT3 directly bind to cyclinD1 promoter. Subclone of full promoter of cyclinD1 into pGL4 increased the luciferase activity while delete or mutation of any of STAT3 binding sites resulted in reductions of luciferase activity. Inhibition of STAT3 decreased cyclinD1 expression to decrease the cell viability and increase rate of apoptosis when exposed to 5-FU treatment.

CONCLUSIONS

Inhibition of STAT3/cyclinD1 pathway increased the sensitivity of colorectal cancer cell to chemotherapy.

Ovarian cancer stem-like cells show induced translineage-differentiation capacity and are suppressed by alkaline phosphatase inhibitor

Spheroid formation is one property of stem cells—such as embryo-derived or neural stem cells—that has been used for the enrichment of cancer stem-like cells (CSLCs). However, it is unclear whether CSLC-derived spheroids are heterogeneous or whether they share common embryonic stemness properties. Understanding these features might lead to novel therapeutic approaches. Ovarian carcinoma is a deadly disease of women. We identified two types of spheroids (SR1 and SR2) from ovarian cancer cell lines and patients' specimens according to their morphology. Both types expressed stemness markers and could self-renew and initiate tumors when a low number of cells were used. Only SR1 could differentiate into multiple-lineage cell types under specific induction conditions. SR1 spheroids could differentiate to SR2 spheroids through epithelial–mesenchymal transition. Alkaline phosphatase (ALP) was highly expressed in SR1 spheroids, decreased in SR2 spheroids, and was absent in differentiated progenies in accordance with the loss of stemness properties. We verified that ALP can be a marker for ovarian CSLCs, and patients with greater ALP expression is related to advanced clinical stages and have a higher risk of recurrence and lower survival rate. The ALP inhibitor, levamisole, disrupted the self-renewal of ovarian CSLCs in vitro and tumor growth in vivo. In summary, this research provides a plastic ovarian cancer stem cell model and a new understanding of the cross-link between stem cells and cancers. This results show that ovarian CSLCs can be suppressed by levamisole. Our findings demonstrated that some ovarian CSLCs may restore ALP activity, and this suggests that inhibition of ALP activity may present a new opportunity for treatment of ovarian cancer.

CDK 4/6 inhibitors sensitize PIK3CA mutant breast cancer to PI3K inhibitors

Activation of the phosphoinositide 3-kinase (PI3K) pathway occurs frequently in breast cancer. However, clinical results of single-agent PI3K inhibitors have been modest to date. A combinatorial drug screen on multiple PIK3CA mutant cancers with decreased sensitivity to PI3K inhibitors revealed that combined CDK 4/6-PI3K inhibition synergistically reduces cell viability. Laboratory studies revealed that sensitive cancers suppress RB phosphorylation upon treatment with single-agent PI3K inhibitors but cancers with reduced sensitivity fail to do so. Similarly, patients' tumors that responded to the PI3K inhibitor BYL719 demonstrated suppression of pRB, while nonresponding tumors showed sustained or increased levels of pRB. Importantly, the combination of PI3K and CDK 4/6 inhibitors overcomes intrinsic and adaptive resistance leading to tumor regressions in PIK3CA mutant xenografts.

CDK 4/6 inhibitors sensitize PIK3CA mutant breast cancer to PI3K inhibitors

Activation of the phosphoinositide 3-kinase (PI3K) pathway occurs frequently in breast cancer. However, clinical results of single-agent PI3K inhibitors have been modest to date. A combinatorial drug screen on multiple PIK3CA mutant cancers with decreased sensitivity to PI3K inhibitors revealed that combined CDK 4/6-PI3K inhibition synergistically reduces cell viability. Laboratory studies revealed that sensitive cancers suppress RB phosphorylation upon treatment with single-agent PI3K inhibitors but cancers with reduced sensitivity fail to do so. Similarly, patients' tumors that responded to the PI3K inhibitor BYL719 demonstrated suppression of pRB, while nonresponding tumors showed sustained or increased levels of pRB. Importantly, the combination of PI3K and CDK 4/6 inhibitors overcomes intrinsic and adaptive resistance leading to tumor regressions in PIK3CA mutant xenografts.

Differential survival trends of stage II colorectal cancer patients relate to promoter methylation status of PCDH10, SPARC, and UCHL1

Surgical excision of colorectal cancer at early clinical stages is highly effective, but 20-30% of patients relapse. Therefore, it is of clinical relevance to identify patients at high risk for recurrence, who would benefit from adjuvant chemotherapy. The objective of this study was to identify prognostic and/or predictive methylation markers in stage II colorectal cancer patients. Therefore, we selected six gene promoters (FZD9, PCDH10 (protocadherin 10), SFRP2, SPARC (secreted protein acidic and rich in cysteine), UCHL1 (ubiquitin carboxyl-terminal hydrolase 1), and WIF1) for methylation analysis in formalin-fixed, paraffin-embedded primary tumor samples of colorectal cancer patients (n=143) who were enrolled in a prospective randomized phase III trial of the Austrian Breast and Colorectal cancer Study Group. Patients were randomized to adjuvant chemotherapy with 5-fluorouracil and leucovorin or surveillance only. Survival analyses revealed that combined evaluation of three promoters (PCDH10, SPARC, and UCHL1) showed differential effects with regard to disease-free survival and overall survival in the two treatment groups (significance level 0.007). In the chemotherapy arm, a statistically insignificant trend for patients without methylation toward longer survival was observed (P=0.069 for disease-free survival and P=0.139 for overall survival). Contrary, patients in the surveillance arm without methylation in their gene promoters had shorter disease-free survival and overall survival (P=0.031 for disease-free survival and P=0.003 for overall survival), indicating a prognostic effect of methylation in this group (test for interaction, P=0.006 for disease-free survival and P=0.018 for overall survival). These results indicate that promoter methylation status of PCDH10, SPARC, and UCHL1 may be used both as prognostic and predictive molecular marker for colorectal cancer patients and, therefore, may facilitate treatment decisions for stage II colorectal cancer.

RNA splicing: a new player in the DNA damage response

It is widely accepted that tumorigenesis is a multistep process characterized by the sequential accumulation of genetic alterations. However, the molecular basis of genomic instability in cancer is still partially understood. The observation that hereditary cancers are often characterized by mutations in DNA repair and checkpoint genes suggests that accumulation of DNA damage is a major contributor to the oncogenic transformation. It is therefore of great interest to identify all the cellular pathways that contribute to the response to DNA damage. Recently, RNA processing has emerged as a novel pathway that may contribute to the maintenance of genome stability. In this review, we illustrate several different mechanisms through which pre-mRNA splicing and genomic stability can influence each other. We specifically focus on the role of splicing factors in the DNA damage response and describe how, in turn, activation of the DDR can influence the activity of splicing factors.