PIK3CA mutations are associated with reduced pathological complete response rates in primary HER2-positive breast cancer: pooled analysis of 967 patients from five prospective trials investigating lapatinib and trastuzumab.

BACKGROUND: The predictive value of PIK3CA mutations in HER2 positive (HER2+) breast cancer treated with neoadjuvant anti-HER2 and chemotherapy has been reported, but the power for subgroup analyses was lacking. PATIENTS AND METHODS: We combined individual patient data from five clinical trials evaluating PIK3CA mutations and associations with pathological complete response (pCR), disease-free survival (DFS) and overall survival (OS). Patients received either trastuzumab (T), lapatinib (L) or the combination T/L in addition to a taxane-based chemotherapy. PIK3CA was genotyped in tumour biopsies taken before therapy. RESULTS: A total of 967 patients were included in this analysis; the median follow-up is 47 months. Overall, the pCR rate was significantly lower in the PIK3CA mutant compared with the wild-type group (16.2% versus 29.6%; P < 0.001). Within the hormone-receptor positive (HR+) subgroup, the PIK3CA mutant group had a pCR rate of only 7.6% compared with 24.2% in the wild-type group (P < 0.001). In contrast, in the HER2+/HR- group, there was no difference in pCR (27.2% versus 36.4%; P = 0.125) according to PIK3CA mutation status (interaction test P = 0.036). According to treatment arm, the pCR rate for mutant versus wild-type was 20.3% versus 27.1% for T (P = 0.343), 11.3% versus 16.9% for L (P = 0.369) and 16.7% versus 39.1% for T/L (P < 0.001). In the HR+ T/L group, the pCR rate was 5.5% versus 33.9% (interaction between HR and PIK3CA genotype P = 0.008). DFS and OS were not significantly different by mutation status, though the incidence rate of events was low. However, HR+/PIK3CA mutant patients seemed to have significantly worse DFS {hazard ratio (HR) 1.56 [95% confidence interval (CI) 1.00-2.45], P = 0.050; Pinteraction = 0.021}. T/L tended to improve DFS compared with T in the wild-type cohort, especially in the HR- group [HR 0.72, 95% CI (0.41-1.25), P = 0.242]. CONCLUSION: Overall PIK3CA mutant/HER2+ tumours had significantly lower pCR rates compared with wild-type tumours, however mainly confined to the HR+/PIK3CA mutant population. No definite conclusions can be drawn regarding survival.

Targeting the RB-E2F pathway in breast cancer.

Mutations of the retinoblastoma tumor-suppressor gene (RB1) or components regulating the CDK-RB-E2F pathway have been identified in nearly every human malignancy. Re-establishing cell cycle control through cyclin-dependent kinase (CDK) inhibition has therefore emerged as an attractive option in the development of targeted cancer therapy. The most successful example of this today is the use of the CDK4/6 inhibitor palbociclib combined with aromatase inhibitors for the treatment of estrogen receptor-positive breast cancers. Multiple studies have demonstrated that the CDK-RB-E2F pathway is critical for the control of cell proliferation. More recently, studies have highlighted additional roles of this pathway, especially E2F transcription factors themselves, in tumor progression, angiogenesis and metastasis. Specific E2Fs also have prognostic value in breast cancer, independent of clinical parameters. We discuss here recent advances in understanding of the RB-E2F pathway in breast cancer. We also discuss the application of genome-wide genetic screening efforts to gain insight into synthetic lethal interactions of CDK4/6 inhibitors in breast cancer for the development of more effective combination therapies.

Opportunities and challenges provided by crosstalk between signalling pathways in cancer.

During evolution, connections between the major signalling pathways were established to provide cells with an ability to deal with perturbations of homeostasis. However, these feedback and crosstalk mechanisms can become a liability in the treatment of cancer, as the inhibition of one cancer-relevant signalling pathway can lead to the activation of a secondary survival pathway that interferes with cancer drug efficacy. In this review, we discuss connections between signalling pathways in relation to cancer therapy and we evaluate the use of genetic approaches to identify pathway crosstalk. We also discuss how insight into connections between signalling pathways can be exploited to design powerful synthetic lethal drug combination therapies for the treatment of cancer.

A chromatin modifier genetic screen identifies SIRT2 as a modulator of response to targeted therapies through the regulation of MEK kinase activity.

Resistance to targeted therapies is a major problem in cancer treatment. The epidermal growth factor receptor (EGFR) antibody drugs are effective in a subset of colorectal cancers, but the molecular mechanisms of resistance are understood poorly. Genes involved in epigenetic regulation are frequently deregulated in cancer, raising the possibility that such genes also contribute to drug resistance. Using a focused RNA interference library for genes involved in epigenetic regulation, we identify sirtuin2 (SIRT2), an NAD(+)-dependent deacetylase, as a modulator of the response to EGFR inhibitors in colon and lung cancer. SIRT2 loss also conferred resistance to BRAF and MEK inhibitors in BRAF mutant melanoma and KRAS mutant colon cancers, respectively. These results warrant further investigation into the potential role of SIRT2 in resistance to drugs that act in the receptor tyrosine kinase-RAS-RAF-MEK-ERK signaling pathway.

Long-term impact of the 70-gene signature on breast cancer outcome.

Several studies have validated the prognostic value of the 70-gene prognosis signature (MammaPrint(R)), but long-term outcome prediction of these patients has not been previously reported. The follow-up of the consecutively treated cohort of 295 patients (<53 years) with invasive breast cancer (T1-2N0-1M0; n = 151 N0, n = 144 N1) diagnosed between 1984 and 1995, in which the 70-gene signature was previously validated, was updated. The median follow-up for this series is now extended to 18.5 years. A significant difference is seen in long-term distant metastasis-free survival (DMFS) for the patients with a low- and a high-risk 70-gene signature (DMFS p < 0.0001), as well as separately for node-negative (DMFS p < 0.0001) and node-positive patients (DMFS p = 0.0004). The 25-year hazard ratios (HRs) for all patients for DMFS and OS were 3.1 (95 % CI 2.02-4.86) and 2.9 (95 % CI 1.90-4.28), respectively. The HRs for DMFS and OS were largest in the first 5 years after diagnosis: 9.6 (95 % CI 4.2-22.1) and 11.3 (95 % CI 3.5-36.4), respectively. The 25-year HRs in the subgroup of node-negative patients for DMFS and OS were 4.57 (95 % CI 2.31-9.04) and 4.73 (95 % CI 2.46-9.07), respectively, and for node-positive patients for DMFS and OS were 2.24 (95 % CI 1.25-4.00) and 1.83 (95 % CI 1.07-3.11), respectively. The 70-gene signature remains prognostic at longer follow-up in patients <53 years of age with stage I and II breast cancer. The 70-gene signature's strongest prognostic power is seen in the first 5 years after diagnosis.

The NuRD complex cooperates with DNMTs to maintain silencing of key colorectal tumor suppressor genes.

Many tumor suppressor genes (TSGs) are silenced through synergistic layers of epigenetic regulation including abnormal DNA hypermethylation of promoter CpG islands, repressive chromatin modifications and enhanced nucleosome deposition over transcription start sites. The protein complexes responsible for silencing of many of such TSGs remain to be identified. Our previous work demonstrated that multiple silenced TSGs in colorectal cancer cells can be partially reactivated by DNA demethylation in cells disrupted for the DNA methyltransferases 1 and 3B (DNMT1 and 3B) or by DNMT inhibitors (DNMTi). Herein, we used proteomic and functional genetic approaches to identify additional proteins that cooperate with DNMTs in silencing these key silenced TSGs in colon cancer cells. We discovered that DNMTs and the core components of the NuRD (Mi-2/nucleosome remodeling and deacetylase) nucleosome remodeling complex, chromo domain helicase DNA-binding protein 4 (CHD4) and histone deacetylase 1 (HDAC1) occupy the promoters of several of these hypermethylated TSGs and physically and functionally interact to maintain their silencing. Consistent with this, we find an inverse relationship between expression of HDAC1 and 2 and these TSGs in a large panel of primary colorectal tumors. We demonstrate that DNMTs and NuRD cooperate to maintain the silencing of several negative regulators of the WNT and other signaling pathways. We find that depletion of CHD4 is synergistic with DNMT inhibition in reducing the viability of colon cancer cells in correlation with reactivation of TSGs, suggesting that their combined inhibition may be beneficial for the treatment of colon cancer. Since CHD4 has ATPase activity, our data identify CHD4 as a potentially novel drug target in cancer.

Targeting the epigenome for treatment of cancer.

Cancer genome analyses have revealed that the enzymes involved in epigenetic gene regulation are frequently deregulated in cancer. Here we describe the enzymes that control the epigenetic state of the cell, how they are affected in cancer and how this knowledge can be exploited to treat cancer with a new arsenal of selective therapies.

The cocaine- and amphetamine-regulated transcript mediates ligand-independent activation of ERα, and is an independent prognostic factor in node-negative breast cancer.

Personalized medicine requires the identification of unambiguous prognostic and predictive biomarkers to inform therapeutic decisions. Within this context, the management of lymph node-negative breast cancer is the subject of much debate with particular emphasis on the requirement for adjuvant chemotherapy. The identification of prognostic and predictive biomarkers in this group of patients is crucial. Here, we demonstrate by tissue microarray and automated image analysis that the cocaine- and amphetamine-regulated transcript (CART) is expressed in primary and metastatic breast cancer and is an independent poor prognostic factor in estrogen receptor (ER)-positive, lymph node-negative tumors in two separate breast cancer cohorts (n=690; P=0.002, 0.013). We also show that CART increases the transcriptional activity of ERα in a ligand-independent manner via the mitogen-activated protein kinase pathway and that CART stimulates an autocrine/paracrine loop within tumor cells to amplify the CART signal. Additionally, we demonstrate that CART expression in ER-positive breast cancer cell lines protects against tamoxifen-mediated cell death and that high CART expression predicts disease outcome in tamoxifen-treated patients in vivo in three independent breast cancer cohorts. We believe that CART profiling will help facilitate stratification of lymph node-negative breast cancer patients into high- and low-risk categories and allow for the personalization of therapy.

Loss-of-function genetic screens as a tool to improve the diagnosis and treatment of cancer.

A major impediment to the effective treatment of cancer is the molecular heterogeneity of the disease, which is also reflected in an equally diverse pattern of clinical responses to therapy. Currently, only few drugs are available that can be used safely and effectively to treat cancer. To improve this situation, the development of novel and highly specific targets for therapy is of utmost importance. Possibly even more importantly, we need better tools to predict which patients will respond to specific therapies. Such drug response biomarkers will be instrumental to individualize the therapy of patients having seemingly similar cancers. In this study, we discuss how RNA interference-based genetic screens can be used to address these two pressing needs in the care for cancer patients.

PRAME expression and clinical outcome of breast cancer.

The tumour antigen PReferentially expressed Antigen of MElanoma (PRAME) is expressed in a variety of malignancies, including breast cancer. We have analysed PRAME gene expression in relation to clinical outcome for 295 primary breast cancer patients. Kaplan-Meier survival curves show a correlation of PRAME expression levels with increased rates of distant metastases and decreased overall patient survival. This correlation existed both for the entire patient group (n=295) and for the subgroup of patients (n=185) who did not receive adjuvant chemotherapy. Multivariable analysis indicated that PRAME is an independent marker of shortened metastasis-free interval in patients who did not receive adjuvant chemotherapy. PRAME expression was associated with tumour grade and negative oestrogen receptor status. We conclude that PRAME expression is a prognostic marker for clinical outcome of breast cancer, independent of traditional clinicopathological markers.

An evaluation of the efficacy of topical application of salicylic acid for the treatment of familial cylindromatosis.

BACKGROUND: Familial cylindromatosis is a rare genetic disorder, giving rise to neoplasms of the skin appendages. We have recently shown that loss of the cylindromatosis tumour suppressor gene leads to activation of NF-kappaB, a transcription factor having antiapoptotic activity. This provides a possible explanation for the deregulated growth of cylindromas. In cell-based assays, salicylate can prevent NF-kappaB activation caused by loss of the cylindromatosis gene, suggesting that salicylic acid application might be a potential treatment for cylindromatosis. OBJECTIVES: To assess the effectiveness of topical application of salicylic acid on familial cylindromas. METHODS: Cylindromas in five patients from four different cylindromatosis families were treated with twice daily and then once daily topical salicylic acid. Clinical response was determined by serial tumour measurements. RESULTS: In total 17 cylindromas in five patients were studied: 12 target lesions and five control lesions. The median size of the cylindromas was 1.0 cm (range, 0.6-2.8 cm). Two of the 12 cylindromas showed a complete remission. Another eight lesions showed some response, but not sufficient to qualify as partial remission. The control lesions remained stable or increased in size. CONCLUSIONS: Salicylic acid is a well-tolerated and potential new treatment for cylindromatosis.

A functionally distinct member of the DP family of E2F subunits.

E2F transcription factors regulate genes involved in cell-cycle progression. In mammalian cells, physiological E2F exists as an E2F/DP heterodimer. Currently, eight E2F and two DP subunits have been characterized. We report here the characterization of a new member of the DP family, DP-4. While DP-4 exhibits certain similarities with members of the DP family, it also possesses a number of significant differences. Thus, DP-4 forms a heterodimer with E2F subunits, binds to the E2F site and associates with pocket proteins including pRb. In contrast to DP-1, however, DP-4/E2F-1 complexes exhibit reduced DNA binding activity. Furthermore, DP-4 interferes with E2F-1-dependent transcription and delays cell-cycle progression. These results highlight an emerging complexity in the DP family of E2F subunits, and suggest that DP-4 may endow E2F heterodimers with distinct transcription properties.

[The Nobel Prize in Physiology or Medicine for 2006 for the discovery of RNA interference]. / Nobelprijs fysiologie of Geneeskunde 2006 voor de ontdekking van RNA-interferentie.

The Nobel Prize in Physiology or Medicine has been awarded to Andrew Fire and Craig Mello for their discovery of RNA interference, i.e. the suppression of gene activity by double-stranded RNA. Small interfering RNA molecules (siRNAs), notably the antisense strand, recognise and inhibit the corresponding mRNA, thereby silencing the appropriate gene. RNA interference can help to determine the function of genes and may assist in the development ofnew drugs. It may also lead to a better understanding of mechanisms of drug resistance. In addition, siRNAs themselves may prove to have therapeutic value as many diseases are the result of alterations in gene activity.

Cancer of the esophagus and gastric cardia: recent advances.

Esophageal cancer and cancer of the gastric cardia, in particular adenocarcinomas, have shown a rapid and largely unexplained increase in incidence in many developed countries around the world. These diseases have a poor prognosis and current therapies have a modest impact on survival. This review presents recent advances in the epidemiology, etiology, diagnosis, staging, prevention and treatment of resectable and advanced disease. Although significant progress has been made in these areas of research and patient management over the past years, prognosis for most patients diagnosed with esophageal cancer or cancer of the gastric cardia remains poor. New diagnostic procedures, improved surgical procedures, combined treatment modalities and new treatment modalities are being evaluated and may be expected to contribute to improved patient outcomes and better palliation of symptoms in the future.

B-myb rescues ras-induced premature senescence, which requires its transactivation domain.

B-myb, a ubiquitously expressed member of the myb gene family, is highly regulated throughout the cell cycle and appears to be required for cell cycle progression. In contrast to its relatives A-myb, c-myb, and v-myb, no transforming activity of B-myb has been reported thus far. We report here that B-myb can rescue senescence induced by an activated ras oncogene in rodent cells in vitro. We show that transformation by B-Myb involves its ability to activate transcription. Similar to other oncogenic transcription factors, such as c-Myc and E2F, we show that B-Myb also has repression activity. We demonstrate that the C-terminus of B-Myb can function as a repressor of transcription, that B-Myb interacts with the repressor molecules BS69 and N-CoR and that the repression function, like the transactivation domain, contributes to B-myb transformation.

Escape from premature senescence is not sufficient for oncogenic transformation by Ras.

Resistance of primary cells to transformation by oncogenic Ras has been attributed to the induction of replicative growth arrest. This irreversible 'fail-safe mechanism' resembles senescence and requires induction by Ras of p19ARF and p53 (refs 3-5). Mutation of either p19ARF or p53 alleviates Ras-induced senescence and facilitates oncogenic transformation by Ras. Here we report that, whereas Rb and p107 are each dispensable for Ras-induced replicative arrest, simultaneous ablation of both genes disrupts Ras-induced senescence and results in unrestrained proliferation. This occurs despite activation by Ras of the p19ARF /p53 pathway, identifying pRb and p107 as essential mediators of Ras-induced antiproliferative p19ARF/p53 signalling. Unexpectedly, in contrast to p19ARF or p53 deficiency, loss of Rb/p107 function does not result in oncogenic transformation by Ras, as Ras-expressing Rb-/-/p107-/- fibroblasts fail to grow anchorage-independently in vitro and are not tumorigenic in vivo. These results demonstrate that in the absence of both Rb and p107 cells are resistant to p19ARF/p53-dependent protection against Ras-induced proliferation, and uncouple escape from Ras-induced premature senescence from oncogenic transformation.

p27kip1-independent cell cycle regulation by MYC.

MYC transcription factors are potent stimulators of cell proliferation. It has been suggested that the CDK-inhibitor p27kip1 is a critical G1 phase cell cycle target of c-MYC. We show here that mouse embryo fibroblasts deficient for both p27kip1 and the related p21cip1 are still responsive to stimulation by c-MYC and can be arrested in G1 by a dominant negative mutant of c-MYC. This growth arrest can be overruled by ectopic expression of E2F or adenovirus E1A, but not by a mutant of E1A defective for binding to retinoblastoma family proteins. We show that fibroblasts with a genetic disruption of all three retinoblastoma family members (pRb, p107 and p130) are unresponsive to a dominant negative c-MYC mutant. These data indicate that p27kip1 is not the only rate limiting cell cycle target of c-MYC and suggest that regulation of E2F is also essential for c-MYC's mitogenic activity.