PTEN mutations are common in sporadic microsatellite stable colorectal cancer

Obesity-Associated Colorectal Cancer

Colorectal cancer (CRC) affects approximately 2 million people worldwide. Obesity is the major risk factor for CRC. In addition, obesity contributes to a chronic inflammatory stage that enhances tumor progression through the secretion of proinflammatory cytokines. In addition to an increased inflammatory response, obesity-associated cancer presents accrued molecular factors related to cancer characteristics, such as genome instability, sustained cell proliferation, telomere dysfunctions, angiogenesis, and microbial alteration, among others. Despite the evidence accumulated over the last few years, the treatments for obesity-associated CRC do not differ from the CRC treatments in normal-weight individuals. In this review, we summarize the current knowledge on obesity-associated cancer, including its epidemiology, risk factors, molecular factors, and current treatments. Finally, we enumerate possible new therapeutic targets that may improve the conditions of obese CRC patients. Obesity is key for the development of CRC, and treatments resulting in the reversal of obesity should be considered as a strategy for improving antineoplastic CRC therapies.

PTEN, PTENP1, microRNAs, and ceRNA Networks: Precision Targeting in Cancer Therapeutics

The phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a well characterised tumour suppressor, playing a critical role in the maintenance of fundamental cellular processes including cell proliferation, migration, metabolism, and survival. Subtle decreases in cellular levels of PTEN result in the development and progression of cancer, hence there is tight regulation of the expression, activity, and cellular half-life of PTEN at the transcriptional, post-transcriptional, and post-translational levels. PTENP1, the processed pseudogene of PTEN, is an important transcriptional and post-transcriptional regulator of PTEN. PTENP1 expression produces sense and antisense transcripts modulating PTEN expression, in conjunction with miRNAs. Due to the high sequence similarity between PTEN and the PTENP1 sense transcript, the transcripts possess common miRNA binding sites with the potential for PTENP1 to compete for the binding, or 'sponging', of miRNAs that would otherwise target the PTEN transcript. PTENP1 therefore acts as a competitive endogenous RNA (ceRNA), competing with PTEN for the binding of specific miRNAs to alter the abundance of PTEN. Transcription from the antisense strand produces two functionally independent isoforms (PTENP1-AS-α and PTENP1-AS-β), which can regulate PTEN transcription. In this review, we provide an overview of the post-transcriptional regulation of PTEN through interaction with its pseudogene, the cellular miRNA milieu and operation of the ceRNA network. Furthermore, its importance in maintaining cellular integrity and how disruption of this PTEN-miRNA-PTENP1 axis may lead to cancer but also provide novel therapeutic opportunities, is discussed. Precision targeting of PTENP1-miRNA mediated regulation of PTEN may present as a viable alternative therapy.

Immunotherapy for Colorectal Cancer: Mechanisms and Predictive Biomarkers

Simple Summary

Late-stage colorectal cancer treatment often involves chemotherapy and radiation that can cause dose-limiting toxicity, and therefore there is great interest in developing targeted therapies for this disease. Immunotherapy is a targeted therapy that uses peptides, cells, antibodies, viruses, or small molecules to engage or train the immune system to kill cancer. Here, we discuss the preclinical and clinical development of immunotherapy for treatment of colorectal cancer and provide an overview of predictive biomarkers for such treatments. We also consider open questions including optimal combination treatments and sensitization of colorectal cancer patients with proficient mismatch repair enzymes.

Abstract

Though early-stage colorectal cancer has a high 5 year survival rate of 65–92% depending on the specific stage, this probability drops to 13% after the cancer metastasizes. Frontline treatments for colorectal cancer such as chemotherapy and radiation often produce dose-limiting toxicities in patients and acquired resistance in cancer cells. Additional targeted treatments are needed to improve patient outcomes and quality of life. Immunotherapy involves treatment with peptides, cells, antibodies, viruses, or small molecules to engage or train the immune system to kill cancer cells. Preclinical and clinical investigations of immunotherapy for treatment of colorectal cancer including immune checkpoint blockade, adoptive cell therapy, monoclonal antibodies, oncolytic viruses, anti-cancer vaccines, and immune system modulators have been promising, but demonstrate limitations for patients with proficient mismatch repair enzymes. In this review, we discuss preclinical and clinical studies investigating immunotherapy for treatment of colorectal cancer and predictive biomarkers for response to these treatments. We also consider open questions including optimal combination treatments to maximize efficacy, minimize toxicity, and prevent acquired resistance and approaches to sensitize mismatch repair-proficient patients to immunotherapy.

The PI3K/Akt/mTOR axis in colorectal cancer: Oncogenic alterations, non-coding RNAs, therapeutic opportunities, and the emerging role of nanoparticles

Colorectal cancer (CRC) is one of the deadliest human malignancies worldwide. Several molecular pathways have been demonstrated to be involved in the initiation and development of CRC which among them, the overactivation of the phosphatidyl-inositol 3-kinase (PI3K)/Akt/mTOR axis is of importance. The current review aims to unravel the mechanisms by which the PI3K/Akt/mTOR pathway affects CRC progression; and also, to summarize the original data obtained from international research laboratories on the oncogenic alterations and polymorphisms affecting this pathway in CRC. Besides, we provide a special focus on the regulatory role of noncoding RNAs targeting the PI3K/Akt/mTOR pathway in this malignancy. Questions on how this axis is involved in the inhibition of apoptosis, in the induction of drug resistance, and the angiogenesis, epithelial to mesenchymal transition, and metastasis are also responded. We also discussed the PI3K/Akt pathway-associated prognostic and predictive biomarkers in CRC. In addition, we provide a general overview of PI3K/Akt/mTOR pathway inhibition whether by chemical-based drugs or by natural-based medications in the context of CRC, either as monotherapy or in combination with other therapeutic agents; however, those treatments might have life-threatening side effects and toxicities. To the best of our knowledge, the current review is one of the first ones highlighting the emerging roles of nanotechnology to overcome challenges related to CRC therapy in the hope that providing a promising platform for the treatment of CRC.

The Novel Phosphatase Domain Mutations Q171R and Y65S Switch PTEN from Tumor Suppressor to Oncogene

Phosphatase and tensin homolog deleted on chromosome 10, or PTEN, is a well-characterized tumor suppressor with both lipid and protein phosphatase activities. PTEN is often downregulated by epigenetic mechanisms such as hypermethylation, which leads to constitutive activation of the PI3K-Akt pathway. Large datasets from next-generation sequencing, however, revealed that mutations in PTEN may not only hamper protein function but may also affect interactions with downstream effectors, leading to variable oncogenic readouts. Here, two novel PTEN mutations, Q171R and Y65S, identified in Filipino colorectal cancer patients, were phenotypically characterized in NIH3T3 and HCT116 cells, alongside the C124S canonical mutant and wild-type controls. The novel mutants increased cellular proliferation, resistance to apoptosis and migratory capacity. They induced gross morphological changes including cytoplasmic shrinkage, increased cellular protrusions and extensive cytoskeletal reorganization. The mutants also induced a modest increase in Akt phosphorylation. Further mechanistic studies will help determine the differential oncogenic potencies of these mutants, and resolve whether the structural constraints imposed by the mutations may have altered associations with downstream effectors.

Redefining the PTEN promoter: Identification of novel upstream transcription start regions

Germline mutation of PTEN is causally observed in Cowden syndrome (CS) and is one of the most common, penetrant risk genes for autism spectrum disorder (ASD). However, the majority of individuals who present with CS-like clinical features are PTEN-mutation negative. Reassessment of PTEN promoter regulation may help explain abnormal PTEN dosage, as only the minimal promoter and coding regions are currently included in diagnostic PTEN mutation analysis. Therefore, we reanalyzed the architecture of the PTEN promoter using next-generation sequencing datasets. Specifically, run-on sequencing assays identified two additional transcription start regions (TSRs) at -2053 and - 1906 basepairs from the canonical start of PTEN, thus extending the PTEN 5'UTR and redefining the PTEN promoter. We show that these novel upstream TSRs are active in cancer cell lines, human cancer, and normal tissue. Further, these TSRs can produce novel PTEN transcripts due to the introduction of new splice donors at -2041, -1826, and - 1355, which may allow for splicing out of the PTEN 5'UTR or the first and second exon in upstream-initiated transcripts. Combining ENCODE ChIP-seq and pertinent literature, we also compile and analyze all transcription factors (TFs) binding at the redefined PTEN locus. Enrichment analyses suggest that TFs bind specifically to the upstream TSRs may be implicated in inflammatory processes. Together, these data redefine the architecture of the PTEN promoter, an important step toward a comprehensive model of PTEN transcription regulation, a basis for future investigations into the new promoters' role in disease pathogenesis.

Effects of molecular markers on the treatment decision and prognosis of colorectal cancer: a narrative review

OBJECTIVE

To summarize the effects of molecular markers on the treatment decision and prognosis of colorectal cancer.

BACKGROUND

Colorectal cancer is a highly heterogeneous disease. Even colorectal cancers of the same pathological type and clinical stage may have significant differences in treatment efficacy and prognosis. There are three main molecular mechanisms for the occurrence and development of colorectal cancer: chromosomal instability (CIN) pathway, microsatellite instability (MSI), and CpG island methylate phenotype (CIMP). There are multiple molecular markers distributed on each pathway.

METHODS

We performed a literature search on the PubMed database for studies published in English (from the date of initiation of the database to the year of 2020) using the following subject terms: "colon cancer", "rectal cancer", "colorectal cancer", "molecular markers", "biomarkers", "treatment strategies", and "prognosis".

CONCLUSIONS

The different expression states of molecular markers have a significant impact on the treatment decision and prognosis of colorectal cancer. Main colorectal cancer molecular markers include MSI and some important genes. Individualized treatments for tumors with different molecular phenotypes have improved the treatment effectiveness for colorectal cancer. The rational use of molecular markers is valuable for treatment decision-making and the prognosis of patients with colorectal cancer.

A synthetically lethal nanomedicine delivering novel inhibitors of polynucleotide kinase 3'-phosphatase (PNKP) for targeted therapy of PTEN-deficient colorectal cancer

Phosphatase and TENsin homolog deleted on chromosome 10 (PTEN) is a major tumor-suppressor protein that is lost in up to 75% of aggressive colorectal cancers (CRC). The co-depletion of PTEN and a DNA repair protein, polynucleotide kinase 3'-phosphatase (PNKP), has been shown to lead to synthetic lethality in several cancer types including CRC. This finding inspired the development of novel PNKP inhibitors as potential new drugs against PTEN-deficient CRC. Here, we report on the in vitro and in vivo evaluation of a nano-encapsulated potent, but poorly water-soluble lead PNKP inhibitor, A83B4C63, as a new targeted therapeutic for PTEN-deficient CRC. Our data confirmed the binding of A83B4C63, as free or nanoparticle (NP) formulation, to intracellular PNKP using the cellular thermal shift assay (CETSA), in vitro and in vivo. Dose escalating toxicity studies in healthy CD-1 mice, based on measurement of animal weight changes and biochemical blood analysis, revealed the safety of both free and nano-encapsulated A83B4C63, at assessed doses of ≤50 mg/kg. Nano-carriers of A83B4C63 effectively inhibited the growth of HCT116/PTEN^-/- xenografts in NIH-III nude mice following intravenous (IV) administration, but not that of wild-type HCT116/PTEN^+/+ xenografts. This was in contrast to IV administration of A83B4C63 solubilized with the aid of Cremophor EL: Ethanol (CE), which led to similar tumor growth to that of formulation excipients (NP or CE without drug) or 5% dextrose. This observation was attributed to the higher levels of A83B4C63 delivered to tumor tissue by its NP formulation. Our data provide evidence for the success of NPs of A83B4C63, as novel synthetically lethal nano-therapeutics in the treatment of PTEN-deficient CRC. This research also highlights the potential of successful application of nanomedicine in the drug development process.

Toward Systems Pathology for PTEN Diagnostics

Germline alterations of the tumor suppressor PTEN have been extensively characterized in patients with PTEN hamartoma tumor syndromes, encompassing subsets of Cowden syndrome, Bannayan-Riley-Ruvalcaba syndrome, Proteus and Proteus-like syndromes, as well as autism spectrum disorder. Studies have shown an increase in the risk of developing specific cancer types in the presence of a germline PTEN mutation. Furthermore, outside of the familial setting, somatic variants of PTEN occur in numerous malignancies. Here we introduce and discuss the prospect of moving toward a systems pathology approach for PTEN diagnostics, incorporating clinical and molecular pathology data with the goal of improving the clinical management of patients with a PTEN mutation. Detection of a germline PTEN mutation can inform cancer surveillance and in the case of somatic mutation, have value in predicting disease course. Given that PTEN functions in the PI3K/AKT/mTOR pathway, identification of a PTEN mutation may highlight new therapeutic opportunities and/or inform therapeutic choices.

Interplay between DNA damage repair and apoptosis shapes cancer evolution through aneuploidy and microsatellite instability

Driver mutations and chromosomal aneuploidy are major determinants of tumorigenesis that exhibit complex relationships. Here, we identify associations between driver mutations and chromosomal aberrations that define two tumor clusters, with distinct regimes of tumor evolution underpinned by unique sets of mutations in different components of DNA damage response. Gastrointestinal and endometrial tumors comprise a separate cluster for which chromosomal-arm aneuploidy and driver mutations are mutually exclusive. The landscape of driver mutations in these tumors is dominated by mutations in DNA repair genes that are further linked to microsatellite instability. The rest of the cancer types show a positive association between driver mutations and aneuploidy, and a characteristic set of mutations that involves primarily genes for components of the apoptotic machinery. The distinct sets of mutated genes derived here show substantial prognostic power and suggest specific vulnerabilities of different cancers that might have therapeutic potential.

Hypermethylation of Corticotropin Releasing Hormone Receptor-2 Gene in Ulcerative Colitis Associated Colorectal Cancer

BACKGROUND/AIM

The difficulty of early diagnosis of colitis associated colorectal cancer (CACRC) due to colonic mucosal changes in long-standing ulcerative colitis (UC) patients is often experienced in daily clinical practice. Noninvasive objective monitoring for cancer development is advantageous for optimizing treatment strategies in UC patients. We aimed to examine the epigenetic alterations occurring in CACRC, focusing on DNA hypermethylation of CpG islands.

MATERIALS AND METHODS

The level of DNA methylation in CpG cites was compared between CACRC and the counterpart non-tumorous mucosa using Infinium HumanMethylation 450K BeadChip.

RESULTS

Our subjects included 3 males and 3 females (median age, 49.5 years). The 450K CpG site DNA methylation microarray revealed that the difference in β value (level of hypermethylation) was the highest for corcicotropin releasing hormone receptor 2 (CRHR2) between CACRC and counterpart non-tumorous mucosa.

CONCLUSION

Detection of hypermethylation of CRHR2 may be promising for cancer screening in UC patients.

Precise Immunodetection of PTEN Protein in Human Neoplasia

PTEN is a major tumor-suppressor protein whose expression and biological activity are frequently diminished in sporadic or inherited cancers. PTEN gene deletion or loss-of-function mutations favor tumor cell growth and are commonly found in clinical practice. In addition, diminished PTEN protein expression is also frequently observed in tumor samples from cancer patients in the absence of PTEN gene alterations. This makes PTEN protein levels a potential biomarker parameter in clinical oncology, which can guide therapeutic decisions. The specific detection of PTEN protein can be achieved by using highly defined anti-PTEN monoclonal antibodies (mAbs), characterized with precision in terms of sensitivity for the detection technique, specificity for PTEN binding, and constraints of epitope recognition. This is especially relevant taking into consideration that PTEN is highly targeted by mutations and posttranslational modifications, and different PTEN protein isoforms exist. The precise characterization of anti-PTEN mAb reactivity is an important step in the validation of these reagents as diagnostic and prognostic tools in clinical oncology, including their routine use in analytical immunohistochemistry (IHC). Here, we review the current status on the use of well-defined anti-PTEN mAbs for PTEN immunodetection in the clinical context and discuss their potential usefulness and limitations for a more precise cancer diagnosis and patient benefit.

PTEN Tumor-Suppressor: The Dam of Stemness in Cancer

PTEN is one of the most frequently inactivated tumor suppressor genes in cancer. Loss or variation in PTEN gene/protein levels is commonly observed in a broad spectrum of human cancers, while germline PTEN mutations cause inherited syndromes that lead to increased risk of tumors. PTEN restrains tumorigenesis through different mechanisms ranging from phosphatase-dependent and independent activities, subcellular localization and protein interaction, modulating a broad array of cellular functions including growth, proliferation, survival, DNA repair, and cell motility. The main target of PTEN phosphatase activity is one of the most significant cell growth and pro-survival signaling pathway in cancer: PI3K/AKT/mTOR. Several shreds of evidence shed light on the critical role of PTEN in normal and cancer stem cells (CSCs) homeostasis, with its loss fostering the CSC compartment in both solid and hematologic malignancies. CSCs are responsible for tumor propagation, metastatic spread, resistance to therapy, and relapse. Thus, understanding how alterations of PTEN levels affect CSC hallmarks could be crucial for the development of successful therapeutic approaches. Here, we discuss the most significant findings on PTEN-mediated control of CSC state. We aim to unravel the role of PTEN in the regulation of key mechanisms specific for CSCs, such as self-renewal, quiescence/cell cycle, Epithelial-to-Mesenchymal-Transition (EMT), with a particular focus on PTEN-based therapy resistance mechanisms and their exploitation for novel therapeutic approaches in cancer treatment.

Genomic profiles of colorectal carcinoma with liver metastases and newly identified fusion genes

Every year, approximately 1.2 million cases of colorectal carcinoma (CRC) are newly diagnosed worldwide. Although metastases to distant organs are often fatal complications of CRC, little information is known as to how such metastatic lesions are formed. To reveal the genetic profiles for CRC metastasis, we conducted whole‐exome RNA sequencing on CRC tumors with liver metastasis (LM) (group A, n = 12) and clinical stage‐matched larger tumors without LM (group B, n = 16). While the somatic mutation profiles were similar among the primary tumors and LM lesions in group A and the tumors in group B, the A‐to‐C nucleotide change in the context of “AAG” was only enriched in the LM regions in group A, suggesting the presence of a DNA damage process specific to metastasis. Genes already known to be associated with CRC were mutated in all groups at a similar frequency, but we detected somatic nonsynonymous mutations in a total of 707 genes in the LM regions, but not in the tumors without LM. Signaling pathways linked to such “LM‐associated” genes were overrepresented for extracellular matrix‐receptor interaction or focal adhesion. Further, fusions of the ADAP1 (ArfGAP with dual PH domain 1) were newly identified in our cohort (3 out of 28 patients), which activated ARF6, an ADAP1‐substrate. Infrequently, mutated genes may play an important role in metastasis formation of CRC. Additionally, recurrent ADAP1 fusion genes were unexpectedly discovered. As these fusions activate small GTPase, further experiments are warranted to examine their contribution to CRC carcinogenesis.

Possible predisposition for colorectal carcinogenesis due to altered gene expressions in normal appearing mucosa from patients with colorectal neoplasia

Background

Investigations of colorectal carcinogenesis have mainly focused on examining neoplastic tissue. With our aim of identifying potentially cancer-predisposing molecular compositions, we chose a different approach by examining endoscopically normal appearing colonic mucosa of patients with and without colorectal neoplasia (CRN). Directed by this focus, we selected 18 genes that were previously found with altered expression in colorectal cancer affected mucosa.

Methods

Biopsies of colonic mucosa were sampled from 27 patients referred for colonoscopy on suspicion of colorectal disease. Of these, 14 patients had present or previous CRN and the remaining 13 patients served as controls. Using qPCR and Western blot technique, we investigated mRNA and protein expressions. Expressions were investigated for selected kinases in the extracellular signal-regulated kinase/mitogen activated protein kinase (ERK/MAPK), the phosphoinositide 3-kinase/Akt, and the Wnt/β-catenin pathways as well as for selected phosphatases and several entities associated with prostaglandin E2 (PGE₂) signaling. Colonic mucosal contents of PGE₂ and PGE₂ metabolites were determined by use of ELISA.

Results

We found up-regulation of ERK1, ERK2, Akt1, Akt2, PLA2G4A, prostanoid receptor EP3 and phosphatase scaffold subunit PPP2R1B mRNA expression in normal appearing colonic mucosa of CRN patients compared to controls.

Conclusion

Present study supports that even normal appearing mucosa of CRN patients differs from that of non-CRN patients at a molecular level. Especially expression of ERK1 mRNA was increased (p = 0.007) in CRN group. ERK1 may therefore be considered a potential candidate gene as predictive biomarker for developing CRN. Further validation in larger cohorts are required to determine such predictive use in translational medicine and clinics.

Assessment of epigenetic alterations and in silico analysis of mutation affecting PTEN expression among Indian cervical cancer patients

Genetic and epigenetic anomalies accountable for genetic dysregulation are the most common aberrations that determine the underlying heterogeneity of the tumor cells. Currently, phosphatase and tensin homolog (PTEN) incongruity has emerged as potent and persuasive malfunctioning in varied human malignancies. In this study, we have analysed the promoter hypermethylation and expression status of PTEN. We identified different mutations in the exonic region of PTEN. Functional consequences of these mutations were explored using in silico techniques. Promoter hypermethylation of PTEN was detected using methylation-specific polymerase chain reaction (MS-PCR), expression analysis was performed with immunohistochemistry (IHC) and mutation by direct sequencing in a total of 168 uterine cervix tumor cases. The findings were statistically correlated with the clinical parameters. In addition, the effect of nonsynonymous mutations was studied with molecular dynamics simulations. PTEN promoter hypermethylation (45.8%) was found to be significantly associated with the of PTEN loss (57.14%, P < 0.0001). Tumor stages, tumor size, lymph node (LN) were found to be significantly correlated with both PTEN promoter hypermethylation and PTEN loss. Histological grade, however, showed a significant association with only PTEN loss. In total, 11.76% of tumors exhibited mutations in exon 5 and 7, out of which E150K of exon 5 showed the highest deviations in the crystal structure of PTEN by in silico analysis. This study provides valuable insights into oncology and paves the path in the development of efficient biomarker and/or imperative therapeutic tool for cervical cancer treatment.

Mechanisms of PTEN loss in cancer: It's all about diversity

PTEN is a phosphatase which metabolises PIP₃, the lipid product of PI 3-Kinase, directly opposing the activation of the oncogenic PI3K/AKT/mTOR signalling network. Accordingly, loss of function of the PTEN tumour suppressor is one of the most common events observed in many types of cancer. Although the mechanisms by which PTEN function is disrupted are diverse, the most frequently observed events are deletion of a single gene copy of PTEN and gene silencing, usually observed in tumours with little or no PTEN protein detectable by immunohistochemistry. Accordingly, with the exceptions of glioblastoma and endometrial cancer, mutations of the PTEN coding sequence are uncommon (<10%) in most types of cancer. Here we review the data relating to PTEN loss in seven common tumour types and discuss mechanisms of PTEN regulation, some of which appear to contribute to reduced PTEN protein levels in cancers.

PTEN lipid phosphatase inactivation links the hippo and PI3K/Akt pathways to induce gastric tumorigenesis

Background

Phosphatase and tensin homolog (PTEN) is an important tumor suppressor gene, and its encoded protein has activities of both a protein phosphatase and a lipid phosphatase. However, the substitution effect of protein phosphatase activity remains unclear. PI3K/Akt is the most common pathway negatively regulated by PTEN. The Hippo and PI3K/Akt pathways have a joint effect in regulating cell proliferation and apoptosis. Therefore, how PTEN lipid phosphatase inactivation contributes to the occurrence and development of gastric cancer and the potential role of the Hippo and PI3K/Akt pathways in PTEN lipid phosphatase inactivation mediated gastric tumorigenesis remain to be explored.

Methods

Immunohistochemical staining was performed to detect the expression of p-PTEN and YAP in a gastric cancer tissue microarray. Stable cell lines expressing a wild-type or dominant-negative mutant PTEN were established. The proliferation and migration of stable cells were detected by MTT, BrdU, and colony-formation, transwell assay and high content analysis in vitro, and tumor growth differences were observed in xenograft nude mice. Changes in the expression of key molecules in the Hippo and Akt signaling pathways were detected by western blot. Nuclear-cytoplasm separation, immunofluorescence and coimmunoprecipitation analyses were conducted to explore the dysregulation of Hippo in the stable cell lines.

Results

PTEN lipid phosphatase inactivation strongly promoted the proliferation and migration of gastric cancer cells in vitro and tumor growth in vivo. A immunohistochemical analysis of gastric cancer tissues revealed a significant correlation between phosphorylated PTEN and nuclear YAP expression, and both were determined to be independent prognostic factors for gastric cancer. Mechanistically, PTEN lipid phosphatase inactivation abolished the MOB1-LATS1/2 interaction, decreased YAP phosphorylation and finally promoted YAP nuclear translocation, which enhanced the synergistic effect of YAP-TEAD, thus inducing cell proliferation and migration. Moreover, PTEN lipid phosphatase inactivation promoted the PI3K/Akt pathway, and disruption of YAP-TEAD-driven transcription decreased the activation of Akt in a dose-dependent manner.

Conclusions

Taken together, our findings indicate that PTEN lipid phosphatase inactivation links the Hippo and PI3K/Akt pathways to promote gastric tumorigenesis and cancer development.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0795-2) contains supplementary material, which is available to authorized users.

Colitic Cancer Develops Through Mutational Alteration Distinct from that in Sporadic Colorectal Cancer: A Comparative Analysis of Mutational Rates at Each Step

BACKGROUND

Patients with ulcerative colitis (UC) are at risk of UC-associated colorectal cancer (CRC); however, little is known about genetic alterations occurring during UC carcinogenesis. We examined mutational changes in patients with colitic cancer and the features that differed between the carcinogenesis of UC and sporadic CRC.

MATERIAL AND METHODS

Specimens were obtained from the non-neoplastic mucosa and cancer cells of 12 patients with colitic cancer. The mutational rate of oncogenes in colitic cancer was analyzed and compared to that of oncogenes in sporadic CRC.

RESULTS

We observed a lower mutation rate in adenomatous polyposis coli (APC) (16.7%(2/12) vs. 75.9%(161/212), respectively, p=0.0001) and KRAS (16.7%(2/12) vs. 42% (89/212), respectively, p=0.04) in colitic cancer than in sporadic CRC. With respect to cadherin 1 (CDH1) and fibroblast growth factor receptor 2 (FGFR2), the mutational rates for non-neoplastic colorectal mucosa were similar to those in sporadic CRC.

CONCLUSION

We demonstrated that mutational rates for APC and KRAS differ between colitic cancer and sporadic CRC. Furthermore, we revealed that CDH1 and FGFR2 become mutated at an earlier stage in colitic carcinogenesis than in sporadic CRC.

PTEN/PTENP1: 'Regulating the regulator of RTK-dependent PI3K/Akt signalling', new targets for cancer therapy

Regulation of the PI-3 kinase (PI3K)/Akt signalling pathway is essential for maintaining the integrity of fundamental cellular processes, cell growth, survival, death and metabolism, and dysregulation of this pathway is implicated in the development and progression of cancers. Receptor tyrosine kinases (RTKs) are major upstream regulators of PI3K/Akt signalling. The phosphatase and tensin homologue (PTEN), a well characterised tumour suppressor, is a prime antagonist of PI3K and therefore a negative regulator of this pathway. Loss or inactivation of PTEN, which occurs in many tumour types, leads to overactivation of RTK/PI3K/Akt signalling driving tumourigenesis. Cellular PTEN levels are tightly regulated by a number of transcriptional, post-transcriptional and post-translational regulatory mechanisms. Of particular interest, transcription of the PTEN pseudogene, PTENP1, produces sense and antisense transcripts that exhibit post-transcriptional and transcriptional modulation of PTEN expression respectively. These additional levels of regulatory complexity governing PTEN expression add to the overall intricacies of the regulation of RTK/PI-3 K/Akt signalling. This review will discuss the regulation of oncogenic PI3K signalling by PTEN (the regulator) with a focus on the modulatory effects of the sense and antisense transcripts of PTENP1 on PTEN expression, and will further explore the potential for new therapeutic opportunities in cancer treatment.

Targeting the PI3K Signalling as a Therapeutic Strategy in Colorectal Cancer

Colorectal cancer (CRC) remains one of the leading causes of cancer mortality worldwide. Regarded as a heterogeneous disease, a number of biomarkers have been proposed to help in the stratification of CRC patients and to enable the selection of the best therapy for each patient towards personalized therapy. However, although the molecular mechanisms underlying the development of CRC have been elucidated, the therapeutic strategies available for these patients are still quite limited. Thus, over the last few years, a multitude of novel targets and therapeutic strategies have emerged focusing on deregulated molecules and pathways that are implicated in cell growth and survival. Particularly relevant in CRC are the activating mutations in the oncogene PIK3CA that frequently occur in concomitancy with KRAS and BRAF mutations and that lead to deregulation of the major signalling pathways PI3K and MAPK, downstream of EGFR. This review focus on the importance of the PI3K signalling in CRC development, on the current knowledge of PI3K inhibition as a therapeutic approach in CRC and on the implications PI3K signalling molecules may have as potential biomarkers and as new targets for directed therapies in CRC patients.

An integrated computational and experimental study uncovers FUT9 as a metabolic driver of colorectal cancer

Metabolic alterations play an important role in cancer and yet, few metabolic cancer driver genes are known. Here we perform a combined genomic and metabolic modeling analysis searching for metabolic drivers of colorectal cancer. Our analysis predicts FUT9, which catalyzes the biosynthesis of Ley glycolipids, as a driver of advanced-stage colon cancer. Experimental testing reveals FUT9's complex dual role; while its knockdown enhances proliferation and migration in monolayers, it suppresses colon cancer cells expansion in tumorspheres and inhibits tumor development in a mouse xenograft models. These results suggest that FUT9's inhibition may attenuate tumor-initiating cells (TICs) that are known to dominate tumorspheres and early tumor growth, but promote bulk tumor cells. In agreement, we find that FUT9 silencing decreases the expression of the colorectal cancer TIC marker CD44 and the level of the OCT4 transcription factor, which is known to support cancer stemness. Beyond its current application, this work presents a novel genomic and metabolic modeling computational approach that can facilitate the systematic discovery of metabolic driver genes in other types of cancer.

Molecular Biomarkers for the Evaluation of Colorectal Cancer: Guideline From the American Society for Clinical Pathology, College of American Pathologists, Association for Molecular Pathology, and American Society of Clinical Oncology

OBJECTIVES

- To develop evidence-based guideline recommendations through a systematic review of the literature to establish standard molecular biomarker testing of colorectal cancer (CRC) tissues to guide epidermal growth factor receptor (EGFR) therapies and conventional chemotherapy regimens.

METHODS

- The American Society for Clinical Pathology, College of American Pathologists, Association for Molecular Pathology, and American Society of Clinical Oncology convened an expert panel to develop an evidence-based guideline to establish standard molecular biomarker testing and guide therapies for patients with CRC. A comprehensive literature search that included more than 4,000 articles was conducted.

RESULTS

- Twenty-one guideline statements were established.

CONCLUSIONS

- Evidence supports mutational testing for EGFR signaling pathway genes, since they provide clinically actionable information as negative predictors of benefit to anti-EGFR monoclonal antibody therapies for targeted therapy of CRC. Mutations in several of the biomarkers have clear prognostic value. Laboratory approaches to operationalize CRC molecular testing are presented.

Molecular Biomarkers for the Evaluation of Colorectal Cancer

Objectives: To develop evidence-based guideline recommendations through a systematic review of the literature to establish standard molecular biomarker testing of colorectal cancer (CRC) tissues to guide epidermal growth factor receptor (EGFR) therapies and conventional chemotherapy regimens. Methods: The American Society for Clinical Pathology, College of American Pathologists, Association for Molecular Pathology, and American Society of Clinical Oncology convened an expert panel to develop an evidence-based guideline to establish standard molecular biomarker testing and guide therapies for patients with CRC. A comprehensive literature search that included more than 4,000 articles was conducted. Results: Twenty-one guideline statements were established. Conclusions: Evidence supports mutational testing for EGFR signaling pathway genes, since they provide clinically actionable information as negative predictors of benefit to anti-EGFR monoclonal antibody therapies for targeted therapy of CRC. Mutations in several of the biomarkers have clear prognostic value. Laboratory approaches to operationalize CRC molecular testing are presented.

Molecular Biomarkers for the Evaluation of Colorectal Cancer: Guideline From the American Society for Clinical Pathology, College of American Pathologists, Association for Molecular Pathology, and American Society of Clinical Oncology

OBJECTIVES

To develop evidence-based guideline recommendations through a systematic review of the literature to establish standard molecular biomarker testing of colorectal cancer (CRC) tissues to guide epidermal growth factor receptor (EGFR) therapies and conventional chemotherapy regimens.

METHODS

The American Society for Clinical Pathology, College of American Pathologists, Association for Molecular Pathology, and American Society of Clinical Oncology convened an expert panel to develop an evidence-based guideline to establish standard molecular biomarker testing and guide therapies for patients with CRC. A comprehensive literature search that included more than 4,000 articles was conducted.

RESULTS

Twenty-one guideline statements were established.

CONCLUSIONS

Evidence supports mutational testing for EGFR signaling pathway genes, since they provide clinically actionable information as negative predictors of benefit to anti-EGFR monoclonal antibody therapies for targeted therapy of CRC. Mutations in several of the biomarkers have clear prognostic value. Laboratory approaches to operationalize CRC molecular testing are presented. Key Words: Molecular diagnostics; Gastrointestinal; Histology; Genetics; Oncology.

Molecular Biomarkers for the Evaluation of Colorectal Cancer: Guideline From the American Society for Clinical Pathology, College of American Pathologists, Association for Molecular Pathology, and the American Society of Clinical Oncology

Purpose Molecular testing of colorectal cancers (CRCs) to improve patient care and outcomes of targeted and conventional therapies has been the center of many recent studies, including clinical trials. Evidence-based recommendations for the molecular testing of CRC tissues to guide epidermal growth factor receptor (EGFR) -targeted therapies and conventional chemotherapy regimens are warranted in clinical practice. The purpose of this guideline is to develop evidence-based recommendations to help establish standard molecular biomarker testing for CRC through a systematic review of the literature. Methods The American Society for Clinical Pathology (ASCP), College of American Pathologists (CAP), Association for Molecular Pathology (AMP), and the American Society of Clinical Oncology (ASCO) convened an Expert Panel to develop an evidence-based guideline to help establish standard molecular biomarker testing, guide targeted therapies, and advance personalized care for patients with CRC. A comprehensive literature search that included over 4,000 articles was conducted to gather data to inform this guideline. Results Twenty-one guideline statements (eight recommendations, 10 expert consensus opinions and three no recommendations) were established. Recommendations Evidence supports mutational testing for genes in the EGFR signaling pathway, since they provide clinically actionable information as negative predictors of benefit to anti-EGFR monoclonal antibody therapies for targeted therapy of CRC. Mutations in several of the biomarkers have clear prognostic value. Laboratory approaches to operationalize molecular testing for predictive and prognostic molecular biomarkers involve selection of assays, type of specimens to be tested, timing of ordering of tests and turnaround time for testing results. Additional information is available at: www.asco.org/CRC-markers-guideline and www.asco.org/guidelineswiki.

Depletion of the triggering receptor expressed on myeloid cells 2 inhibits progression of renal cell carcinoma via regulating related protein expression and PTEN-PI3K/Akt pathway

The triggering receptor expressed on myeloid cells 2 (TREM-2) is suggested to be involved in the development of certain human malignancies. However, the functions of TREM-2 in renal cell carcinoma (RCC) are still less known. To reveal the effects of TREM-2 on the RCC progression, we examined the TREM-2 expression in RCC tumor tissues. Then, we analyzed the cell proliferation, cell apoptosis, cell cycle and expression of the relative factors in two selected RCC cell lines post RNA interference. We also analyzed the functions of TREM-2 in an in vivo nude mouse model. We found that, the expression of TREM-2 was abnormally elevated in RCC tumor tissues. Silencing TREM-2 inhibited cell growth, induced G1 phase arrest of cell cycle and cell apoptosis in RCC cells. In vivo, the results showed that depletion of TREM-2 significantly inhibited the ACHN tumor growth in the nude mouse model. The analysis of relative protein factors suggested that silencing TREM-2 downregulated the expression levels of Bcl2 and PCNA, and upregulated the expression levels of Bax and caspase-3 in RCC cell lines. Depletion of TREM-2 inactivated PI3K/Akt pathway through increasing the expression of PTEN. Taken together, TREM-2 acts as an oncogene in the development of RCC and can be considered as a novel therapeutic factor in the treatment of RCC.

Gene heterogeneity in metastasis of colorectal cancer to the lung

Colorectal cancer (CRC) as a heterogeneous disease, is one of the most common and serious cancers with high metastases and mortality. Lung is one of the most common sites of CRC metastases with high heterogeneity between cells, pathways, or molecules. The present review will focus on potential roles of gene heterogeneity in KRAS pathway in the development of CRC metastasis to lung and clinical therapies, which would lead to better understanding of the metastatic control and benefit to the treatment of metastases. KRAS is the central relay for pathways originating at the epidermal growth factor receptor (EGFR) family. KRAS mutation exists in about 40% CRC, associated with higher cumulative incidence of CRC lung metastasis, and acts as an independent predictor of metastasis to lung. Mutations in KRAS can lead to poor response of patients to panitumumab, and inferior progression-free survival. However, most patients with KRAS wild-type tumors still do not respond, which indicates other mutations. Phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) mutation was associated with lung metastases in metastatic colorectal cancer. PIK3CA mutation in exon 20 was found to be correlated with patient survival in the metastatic setting after the treatment with cetuximab and chemotherapy. The heterogeneity of KRAS pathway was found in the phosphatase and tensin homologue deleted on chromosome ten loss, disheveled binding antagonist of beta catenin 2 overexpression and increased dual-specificity protein phosphatase 4 expression of CRC lung metastasis.

In depth evaluation of the prognostic and predictive utility of PTEN immunohistochemistry in colorectal carcinomas: performance of three antibodies with emphasis on intracellular and intratumoral heterogeneity

Background

Phosphatase and tensin homolog deleted in chromosome 10 (PTEN) loss of function is frequently detected in advanced colorectal cancer. Its detection is thought to have prognostic significance and it is being considered to predict responsiveness to anti-EGFR therapy. Unfortunately, while immunohistochemical assessment of PTEN expression is widespread, it lacks standardization and the results are hardly comparable across the available publications.

Methods

Retrospectively collected, formalin-fixed and paraffin-embedded colorectal tumor tissue samples from 55 patients were combined into tissue microarray (TMA) blocks. We used three different PTEN antibodies to determine the frequency, intensity and intracellular pattern of PTEN immunohistochemical labeling: Neomarkers, Dako and CellSignaling. We evaluated the aforementioned parameters in selected regions of colorectal cancers and in their lymph node metastases by using three scoring methods that take into consideration both staining frequency and intensity (H1-H3-score). We also evaluated intracellular localization.

Results

The Dako and CellSignaling antibodies stained predominantly cytoplasms, while the Neomarkers antibody specifically stained cell nuclei. PTEN H-scores were significantly lower in all tumor areas as compared to the normal colonic mucosa based on staining with the DAKO and CellSignaling antibodies. Intratumoral regional differences or differences between matching tumors and metastases were not detected with any of the antibodies. Neither Dako, neither CellSignaling, nor the Neomarkers antibodies revealed a significant correlation between PTEN expression and pT, Dukes/MAC and clinical stage. KRAS status, histological grade correlated with PTEN H-scores based on staining with the Neomarkers antibody. PTEN H-scores did not correlate with MMR status. PTEN H-scores did not show any correlation with relapse-free survival based on staining with either antibody.

Conclusions

While PTEN expression decreased in colorectal cancer according to two antibodies, neither of the three applied PTEN antibodies could justify significant correlation with clinicopathological data, nor had prognostic value. Thus, we might conclude that immunohistochemical PTEN investigation remains a challenge requiring more standardized evaluation on larger number of cases to clarify its utility as a prognostic and predictive tool in CRC. The standardization of immunohistochemical method is key in the evaluation process, which is further discussed.

Electronic supplementary material

The online version of this article (doi:10.1186/s13000-016-0508-0) contains supplementary material, which is available to authorized users.

BCL-3 expression promotes colorectal tumorigenesis through activation of AKT signalling

OBJECTIVE

Colorectal cancer remains the fourth most common cause of cancer-related mortality worldwide. Here we investigate the role of nuclear factor-κB (NF-κB) co-factor B-cell CLL/lymphoma 3 (BCL-3) in promoting colorectal tumour cell survival.

DESIGN

Immunohistochemistry was carried out on 47 tumour samples and normal tissue from resection margins. The role of BCL-3/NF-κB complexes on cell growth was studied in vivo and in vitro using an siRNA approach and exogenous BCL-3 expression in colorectal adenoma and carcinoma cells. The question whether BCL-3 activated the AKT/protein kinase B (PKB) pathway in colorectal tumour cells was addressed by western blotting and confocal microscopy, and the ability of 5-aminosalicylic acid (5-ASA) to suppress BCL-3 expression was also investigated.

RESULTS

We report increased BCL-3 expression in human colorectal cancers and demonstrate that BCL-3 expression promotes tumour cell survival in vitro and tumour growth in mouse xenografts in vivo, dependent on interaction with NF-κB p50 or p52 homodimers. We show that BCL-3 promotes cell survival under conditions relevant to the tumour microenvironment, protecting both colorectal adenoma and carcinoma cells from apoptosis via activation of the AKT survival pathway: AKT activation is mediated via both PI3K and mammalian target of rapamycin (mTOR) pathways, leading to phosphorylation of downstream targets GSK-3β and FoxO1/3a. Treatment with 5-ASA suppressed BCL-3 expression in colorectal cancer cells.

CONCLUSIONS

Our study helps to unravel the mechanism by which BCL-3 is linked to poor prognosis in colorectal cancer; we suggest that targeting BCL-3 activity represents an exciting therapeutic opportunity potentially increasing the sensitivity of tumour cells to conventional therapy.

Patterns of somatic uniparental disomy identify novel tumor suppressor genes in colorectal cancer

Colorectal cancer (CRC) is characterized by specific patterns of copy number alterations (CNAs), which helped with the identification of driver oncogenes and tumor suppressor genes (TSGs). More recently, the usage of single nucleotide polymorphism arrays provided information of copy number neutral loss of heterozygosity, thus suggesting the occurrence of somatic uniparental disomy (UPD) and uniparental polysomy (UPP) events. The aim of this study is to establish an integrative profiling of recurrent UPDs/UPPs and CNAs in sporadic CRC. Our results indicate that regions showing high frequencies of UPD/UPP mostly coincide with regions typically involved in genomic losses. Among them, chromosome arms 3p, 5q, 9q, 10q, 14q, 17p, 17q, 20p, 21q and 22q preferentially showed UPDs/UPPs over genomic losses suggesting that tumor cells must maintain the disomic state of certain genes to favor cellular fitness. A meta-analysis using over 300 samples from The Cancer Genome Atlas confirmed our findings. Several regions affected by recurrent UPDs/UPPs contain well-known TSGs, as well as novel candidates such as ARID1A, DLC1, TCF7L2 and DMBT1. In addition, VCAN, FLT4, SFRP1 and GAS7 were also frequently involved in regions of UPD/UPP and displayed high levels of methylation. Finally, sequencing and fluorescence in situ hybridization analysis of the gene APC underlined that a somatic UPD event might represent the second hit to achieve biallelic inactivation of this TSG in colorectal tumors. In summary, our data define a profile of somatic UPDs/UPPs in sporadic CRC and highlights the importance of these events as a mechanism to achieve the inactivation of TSGs.

Nuclear localized Akt enhances breast cancer stem-like cells through counter-regulation of p21(Waf1/Cip1) and p27(kip1)

Cancer stem-like cells (CSCs) are a rare subpopulation of cancer cells capable of propagating the disease and causing cancer recurrence. In this study, we found that the cellular localization of PKB/Akt kinase affects the maintenance of CSCs. When Akt tagged with nuclear localization signal (Akt-NLS) was overexpressed in SKBR3 and MDA-MB468 cells, these cells showed a 10-15% increase in the number of cells with CSCs enhanced ALDH activity and demonstrated a CD44(+High)/CD24(-Low) phenotype. This effect was completely reversed in the presence of Akt-specific inhibitor, triciribine. Furthermore, cells overexpressing Akt or Akt-NLS were less likely to be in G0/G1 phase of the cell cycle by inactivating p21(Waf1/Cip1) and exhibited increased clonogenicity and proliferation as assayed by colony-forming assay (mammosphere formation). Thus, our data emphasize the importance the intracellular localization of Akt has on stemness in human breast cancer cells. It also indicates a new robust way for improving the enrichment and culture of CSCs for experimental purposes. Hence, it allows for the development of simpler protocols to study stemness, clonogenic potency, and screening of new chemotherapeutic agents that preferentially target cancer stem cells.

SUMMARY

The presented data, (i) shows new, stemness-promoting role of nuclear Akt/PKB kinase, (ii) it underlines the effects of nuclear Akt on cell cycle regulation, and finally (iii) it suggests new ways to study cancer stem-like cells.

Increased proliferation in atypical hyperplasia/endometrioid intraepithelial neoplasia of the endometrium with concurrent inactivation of ARID1A and PTEN tumour suppressors

Abstract Uterine endometrioid carcinoma is the most common neoplastic disease in the female genital tract and develops from a common precursor lesion, atypical hyperplasia/endometrioid intraepithelial neoplasia (AH/EIN). Although the genomic landscape of endometrioid carcinoma has been recently revealed, the molecular alterations that contribute to tumour progression from AH/EIN to carcinoma remain to be elucidated. In this study, we used immunohistochemistry to determine if loss of expression of two of the most commonly mutated tumour suppressors in endometrioid carcinoma, PTEN and ARID1A, was associated with increased proliferation in AH/EIN. We found that 80 (70%) of 114 cases exhibited decreased or undetectable PTEN and 17 (15%) of 114 cases had focal loss of ARID1A staining. ARID1A loss was focal, while PTEN loss was diffuse, and all specimens with ARID1A loss had concurrent PTEN loss (p = 0.0003). Mapping the distribution of PTEN and ARID1A staining in the same specimens demonstrated that all AH/EIN areas with ARID1A loss were geographically nested within the areas of PTEN loss. A significant increase in the proliferative activity was observed in areas of AH/EIN with concurrent loss of PTEN and ARID1A compared to immediately adjacent AH/EIN areas showing only PTEN loss. In a cell culture system, co‐silencing of ARID1A and PTEN in human endometrial epithelial cells increased cellular proliferation to a greater degree than silencing either ARID1A or PTEN alone. These results suggest an essential gatekeeper role for ARID1A that prevents PTEN inactivation from promoting cellular proliferation in the transition of pre‐cancerous lesions to uterine endometrioid carcinoma.

A comprehensive analysis of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) loss in colorectal cancer

Background

Alterations of PTEN, regulator of the PTEN/PI3K-AKT pathway, are common in several types of cancer. This study aimed to do comprehensive analysis of PTEN in colorectal cancer patients.

Methods

Totally, 198 colorectal cancer patients who received surgery at Taipei Veterans General Hospital from 2006 to 2008 were enrolled. Mutations, loss of protein expression, promoter hypermethylation, and DNA copy number of PTEN were analyzed by sequencing, immunohistochemistry, methylation-specific polymerase chain reaction PCR, and quantitative (QPCR), respectively, and correlated with clinicopathological features and patients’ outcome.

Results

Genomic mutations, loss of protein expression, promoter hypermethylation, and decreased DNA copy number of PTEN were found in 4 (2.02 %), 68 (34.3 %), 54 (27.3 %), and 36 (18.2 %) tumors, respectively. Of these 68 tumors with loss expression of PTEN, 34 (50 %) tumors had promoter methylation and 18 (26.5 %) had decreased DNA copy number. All four tumors with PTEN mutations demonstrated loss of PTEN expression. In the stage I disease, frequency of loss of PTEN expression was 20 % and significantly increased to 56.9 % in stage IV disease. Either loss expression of PTEN, PTEN hypermethylation or decreased PTEN copy number was not associated with colorectal cancer (CRC) patients’ outcome.

Conclusions

PTEN alterations were found in up to one-third of colorectal cancers but did not impact CRC patients’ prognosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12957-015-0601-y) contains supplementary material, which is available to authorized users.

A genetic dissection of intestinal fat-soluble vitamin and carotenoid absorption

Carotenoids are currently investigated regarding their potential to lower the risk of chronic disease and to combat vitamin A deficiency. Surprisingly, responses to dietary supplementation with these compounds are quite variable between individuals. Genome-wide studies have associated common genetic polymorphisms in the BCO1 gene with this variability. The BCO1 gene encodes an enzyme that is expressed in the intestine and converts provitamin A carotenoids to vitamin A-aldehyde. However, it is not clear how this enzyme can impact the bioavailability and metabolism of other carotenoids such as xanthophyll. We here provide evidence that BCO1 is a key component of a regulatory network that controls the absorption of carotenoids and fat-soluble vitamins. In this process, conversion of β-carotene to vitamin A by BCO1 induces via retinoid signaling the expression of the intestinal homeobox transcription factor ISX. Subsequently, ISX binds to conserved DNA-binding motifs upstream of the BCO1 and SCARB1 genes. SCARB1 encodes a membrane protein that facilitates absorption of fat-soluble vitamins and carotenoids. In keeping with its role as a transcriptional repressor, SCARB1 protein levels are significantly increased in the intestine of ISX-deficient mice. This increase results in augmented absorption and tissue accumulation of xanthophyll carotenoids and tocopherols. Our study shows that fat-soluble vitamin and carotenoid absorption is controlled by a BCO1-dependent negative feedback regulation. Thus, our findings provide a molecular framework for the controversial relationship between genetics and fat-soluble vitamin status in the human population.

MicroRNA‑135b regulates the stability of PTEN and promotes glycolysis by targeting USP13 in human colorectal cancers

Dysregulation of microRNAs has been reported to be involved in the progression of human colorectal cancers (CRCs). Loss of the adenomatous polyposis coli (APC) gene is a common initiating event in CRCs. PTEN inactivation by mutation or allelic loss also occurs in CRCs. miR‑135b was reported to be upregulated in CRCs and its overexpression was due to APC/β‑catenin and PTEN/PI3K pathway deregulation. APC was proven to be a target of miR‑135b and forms a feedback loop with miR‑135b. In the present study, we found that ubiquitin‑specific peptidase 13 (USP13) was a target of miR‑135b. miR‑135b downregulated the expression of USP13, and reduced the stability of PTEN. miR‑135b promoted cell proliferation and glycolysis that could be reversed by the overexpression of USP13 or PTEN. Moreover, knockdown of USP13 upregulated the levels of endogenous miR‑135b, but not those in CRC cells with PTEN mutation. The results showed positive feedback loops between miR‑135b and PTEN inactivation in CRCs.

Portrait of the PI3K/AKT pathway in colorectal cancer

PI3K/AKT signaling leads to reduced apoptosis, stimulates cell growth and increases proliferation. Under normal conditions, PI3K/AKT activation is tightly controlled and dependent on both extracellular growth signals and the availability of amino acids and glucose. Genetic aberrations leading to PI3K/AKT hyper-activation are observed at considerable frequency in all major nodes in most tumors. In colorectal cancer the most commonly observed pathway changes are IGF2 overexpression, PIK3CA mutations and PTEN mutations and deletions. Combined, these alterations are found in about 40% of large bowel tumors. In addition, but not mutually exclusive to these, KRAS mutations are observed at a similar frequency. There are however additional, less frequent and more poorly understood events that may also push the PI3K/AKT pathway into overdrive and thus promote malignant growth. Here we discuss aberrations of components at the genetic, epigenetic, transcriptional, post-transcriptional, translational and post-translational level where perturbations may drive excessive PI3K/AKT signaling. Integrating multiple molecular levels will advance our understanding of this cancer critical circuit and more importantly, improve our ability to pharmacologically target the pathway in view of clonal development, tumor heterogeneity and drug resistance mechanisms. In this review, we revisit the PI3K/AKT pathway cancer susceptibility syndromes, summarize the known aberrations at the different regulatory levels and the prognostic and predictive values of these alterations in colorectal cancer.

The PI3K/AKT/mTOR pathway in the pathophysiology and treatment of pituitary adenomas

Pituitary adenomas are common intracranial neoplasms. Patients with these tumors exhibit a wide range of clinically challenging problems, stemming either from results of sellar mass effect in pituitary macroadenoma or the diverse effects of aberrant hormone production by adenoma cells. While some patients are cured/controlled by surgical resection and/or medical therapy, a proportion of patients exhibit tumors that are refractory to current modalities. New therapeutic approaches are needed for these patients. Activation of the AKT/phophotidylinositide-3-kinase pathway, including mTOR activation, is common in human neoplasia, and a number of therapeutic approaches are being employed to neutralize activation of this pathway in human cancer. This review examines the role of this pathway in pituitary tumors with respect to tumor biology and its potential role as a therapeutic target.

Predictive biomarkers of response to anti-EGF receptor monoclonal antibody therapies

SUMMARY 

The EGF receptor (EGFR) pathway plays an important role in the progression of several carcinomas, including colorectal cancer (CRC). The EGFR has emerged as a candidate for targeted therapy for CRC. Two monoclonal antibodies used to inhibit the EGFR signaling pathway are cetuximab and panitumumab. Both these monoclonal antibodies inhibit tumor-promoting activities, such as tumor cell proliferation, survival, angiogenesis and metastasis. However, only a subpopulation of metastatic CRC patients responds to such therapy. Constitutive activation within the pathway gives rise to other aberrantly expressed biomarkers that are able to circumvent the anti-EGFR treatment and confer resistance. Mechanisms of resistance and the value of these emerging predictive biomarkers in the clinical setting are discussed in this review.

PTEN mutation, loss of heterozygosity, promoter methylation and expression in colorectal carcinoma: two hits on the gene?

The phosphatase and tensin homologue (PTEN) gene is considered to be a tumour-suppressor gene in various types of cancer, colorectal carcinoma among them. According to the 'two-hit' tumour-suppressor gene concept, inactivation occurs by any combination of the following three pathogenetic processes: mutation, loss of one allele [i.e. loss of heterozygosity (LOH)] or promoter methylation. To determine the frequencies of PTEN tumour-suppressor gene features in colorectal carcinoma, we used DNA from colorectal carcinoma xenografts/primary tumour cell lines (N=22) or neoplastic glands isolated by laser-capture microdissection (N=20). Sequencing exons 1-9 of the gene revealed a total of 8 somatic mutations in 5 tumours (3 with high-degree microsatellite instability). In 1 tumour, a truncating mutation of one allele was combined with two missense mutations of the other allele. Polymorphic microsatellite marker analyses (D10S5412, D10S579 and D10S1765) showed complete loss of one allele (i.e. LOH sensu stricto) in 3 tumours, but combined LOH and mutation was found only once. Promoter methylation, tested by MethyLight technology, was found in only 1 of the tumours, not combined with mutation or LOH. In contrast, by immunohistochemistry (mAb 6H2.1), reduction or even loss of PTEN expression was found in 18 tumours. Taken together, PTEN downregulation is a fairly frequent event in colorectal carcinoma, but this apparently is not usually caused by two hits on the gene.

Genetic unraveling of colorectal cancer

Colorectal cancer is a common disease in both men and women (being the third most common cancer in men and the second most common among women) and thus represents an important and serious public health issue, especially in the western world. Although it is a well-established fact that cancers of the large intestine produce symptoms relatively earlier at a stage that can be easily cured by resection, a large number of people lose their lives to this deadly disease each year. Recent times have seen an important change in the incidence of colorectal cancer in different parts of the world. The etiology of colorectal cancer is multifactorial and is likely to involve the actions of genes at multiple levels along the multistage carcinogenesis process. Exhaustive efforts have been made out in the direction of unraveling the role of various environmental factors, gene mutations, and polymorphisms worldwide (as well as in Kashmir-"a valley of gastrointestinal cancers") that have got a role to play in the development of this disease so that antitumor drugs could be developed against this cancer, first, and, finally, the responsiveness or resistance to these agents could be understood for combating this global issue.

Can we accurately report PTEN status in advanced colorectal cancer?

BACKGROUND

Loss of phosphatase and tensin homologue (PTEN) function evaluated by loss of PTEN protein expression on immunohistochemistry (IHC) has been reported as both prognostic in metastatic colorectal cancer and predictive of response to anti-EGFR monoclonal antibodies although results remain uncertain. Difficulties in the methodological assessment of PTEN are likely to be a major contributor to recent conflicting results.

METHODS

We assessed loss of PTEN function in 51 colorectal cancer specimens using Taqman® copy number variation (CNV) and IHC. Two blinded pathologists performed independent IHC assessment on each specimen and inter-observer variability of IHC assessment and concordance of IHC versus Taqman® CNV was assessed.

RESULTS

Concordance between pathologists (PTEN loss vs no loss) on IHC assessment was 37/51 (73%). In specimens with concordant IHC assessment, concordance between IHC and Taqman® copy number in PTEN loss assessment was 25/37 (68%).

CONCLUSION

Assessment PTEN loss in colorectal cancer is limited by the inter-observer variability of IHC, and discordance of CNV with loss of protein expression. An understanding of the genetic mechanisms of PTEN loss and implementation of improved and standardized methodologies of PTEN assessment are required to clarify the role of PTEN as a biomarker in colorectal cancer.

Quantitative mass spectrometry for colorectal cancer proteomics

This review documents the uses of quantitative MS applied to colorectal cancer (CRC) proteomics for biomarker discovery and molecular pathway profiling. Investigators are adopting various labeling and label-free MS approaches to quantitate differential protein levels in cells, tumors, and plasma/serum. We comprehensively review recent uses of this technology to examine mouse models of CRC, CRC cell lines, their secretomes and subcellular fractions, CRC tumors, CRC patient plasma/serum, and stool samples. For biomarker discovery these approaches are uncovering proteins with potential diagnostic and prognostic utility, while in vitro cell culture experiments are characterizing proteomic and phosphoproteomic responses to disrupted signaling pathways due to mutations or to inhibition of drugable enzymes.

Functions and Regulation of the PTEN Gene in Colorectal Cancer

Phosphatase and TENsin homolog deleted on chromosome 10 (PTEN) is a tumor suppressor gene located at chromosome 10q23.31, encoding for a 403-amino acid protein that possesses both lipid and protein phosphatase activities. The main function of PTEN is to block the PI3K pathway by dephosphorylating phosphatidylinositol (PI) 3,4,5-triphosphate to PI-4,5-bisphosphate thus counteracting PI3K function. PTEN inactivation is a frequent event in many cancer types and can occur through various genetic alterations including point mutations, large chromosomal deletions, and epigenetic mechanisms. In colorectal cancer (CRC) PTEN is altered through mixed genetic/epigenetic mechanisms (typically: mutations and promoter hypermethylation or 10q23 LOH and promoter hypermethylation), which lead to the biallelic inactivation of the protein in 20–30% of cases. The role of PTEN as a prognostic and predictive factor in CRC has been addressed by relatively few works. This review is focused on the report and on the discussion of the studies investigating these aspects. Overall, at the moment, there are conflicting results and, therefore it has not been clarified whether PTEN might play a prognostic role in CRC. The same is valid also for the predictive role, leading to the fact that PTEN evaluation cannot be used in routinely diagnosis for the early identification of patients who might be addressed to the treatment with EGFR-targeted therapies, at odds with other genetic alterations belonging to EGFR-downstream pathways. The reason of discordant results may be attributable to several issues: (1) the size of the analyzed cohort, (2) patients inclusion criteria, (3) the methods of assessing PTEN alteration. In particular, there are no standardized methods to evaluate this marker, especially for immunohistochemistry, a technique suffering of intra and inter-observer variability due to the semi-quantitative character of such an analysis. In conclusion, much work, especially in large and homogeneous cohorts of cases from different laboratories, has to be done before the establishment of PTEN as prognostic or predictive marker in CRC.

MC1R is a potent regulator of PTEN after UV exposure in melanocytes

The individuals carrying melanocortin-1 receptor (MC1R) variants, especially those associated with red hair color, fair skin, and poor tanning ability (RHC trait), are more prone to melanoma; however, the underlying mechanism is poorly defined. Here, we report that UVB exposure triggers phosphatase and tensin homolog (PTEN) interaction with wild-type (WT), but not RHC-associated MC1R variants, which protects PTEN from WWP2-mediated degradation, leading to AKT inactivation. Strikingly, the biological consequences of the failure of MC1R variants to suppress PI3K/AKT signaling are highly context dependent. In primary melanocytes, hyperactivation of PI3K/AKT signaling leads to premature senescence; in the presence of BRAF(V600E), MC1R deficiency-induced elevated PI3K/AKT signaling drives oncogenic transformation. These studies establish the MC1R-PTEN axis as a central regulator for melanocytes' response to UVB exposure and reveal the molecular basis underlying the association between MC1R variants and melanomagenesis.

Phosphatidylinositol-3-kinase pathway aberrations in gastric and colorectal cancer: meta-analysis, co-occurrence and ethnic variation

Inhibition of the phosphatidylinositol-3-kinase (PI3K) signaling pathway is a cancer treatment strategy that has entered into clinical trials. We performed a meta-analysis on the frequency of prominent genetic (PIK3CA mutation, PIK3CA amplification and PTEN deletion) and protein expression (high PI3K, PTEN loss and high pAkt) aberrations in the PI3K pathway in gastric cancer (GC) and colorectal cancer (CRC). We also performed laboratory analysis to investigate the co-occurrence of these aberrations. The meta-analysis indicated that East Asian and Caucasian GC patients differ significantly for the frequencies of PIK3CA Exon 9 and 20 mutations (7% vs. 15%, respectively), PTEN deletion (21% vs. 4%) and PTEN loss (47% vs. 78%), while CRC patients differed for PTEN loss (57% vs. 26%). High study heterogeneity (I(2) > 80) was observed for all aberrations except PIK3CA mutations. Laboratory analysis of tumors from East Asian patients revealed significant differences between GC (n = 79) and CRC (n = 116) for the frequencies of PIK3CA amplification (46% vs. 4%) and PTEN loss (54% vs. 78%). The incidence of GC cases with 0, 1, 2 and 3 concurrent aberrations was 14%, 52%, 27% and 8%, respectively, while for CRC it was 10%, 60%, 25% and 4%, respectively. Our study consolidates knowledge on the frequency, co-occurrence and clinical relevance of PI3K pathway aberrations in GC and CRC. Up to 86% of GC and 90% of CRC have at least one aberration in the PI3K pathway, and there are significant differences in the frequencies of these aberrations according to cancer type and ethnicity.

A new mathematical approach for qualitative modeling of the insulin-TOR-MAPK network

In this paper we develop a novel mathematical model of the insulin-TOR-MAPK signaling network that controls growth. Most data on the properties of the insulin and MAPK signaling networks are static and the responses to experimental interventions, such as knockouts, overexpression, and hormonal input are typically reported as scaled quantities. The modeling paradigm we develop here uses scaled variables and is ideally suited to simulate systems in which much of the available data are scaled. Our mathematical representation of signaling networks provides a way to reconcile theory and experiments, thus leading to a better understanding of the properties and function of these signaling networks. We test the performance of the model against a broad diversity of experimental data. The model correctly reproduces experimental insulin dose-response relationships. We study the interaction between insulin and MAPK signaling in the control of protein synthesis, and the interactions between amino acids, insulin and TOR signaling. We study the effects of variation in FOXO expression on protein synthesis and glucose transport capacity, and show that a FOXO knockout can partially rescue protein synthesis capacity of an insulin receptor (INR) knockout. We conclude that the modeling paradigm we develop provides a simple tool to investigate the qualitative properties of signaling networks.

PIK3CA and PTEN gene and exon mutation-specific clinicopathologic and molecular associations in colorectal cancer

PURPOSE

PIK3CA and PTEN mutations are prevalent in colorectal cancer and potential markers of response to mitogen-activated protein/extracellular signal-regulated kinase inhibitors and anti-EGF receptor antibody therapy. Relationships between phosphoinositide 3-kinase (PI3K) pathway mutation, clinicopathologic characteristics, molecular features, and prognosis remain controversial.

EXPERIMENTAL DESIGN

A total of 1,093 stage I-IV colorectal cancers were screened for PIK3CA (exons 9 and 20), KRAS (codons 12-13), BRAF (codon 600) mutations, and microsatellite instability (MSI). PTEN (exons 3-8) and CpG island methylator phenotype (CIMP) status were determined in 744 and 489 cases. PIK3CA data were integrated with 17 previous reports (n = 5,594).

RESULTS

PIK3CA and PTEN mutations were identified in 11.9% and 5.8% of colorectal cancers. PTEN mutation was associated with proximal tumors, mucinous histology, MSI-high (MSI-H), CIMP-high (CIMP-H), and BRAF mutation (P < 0.02). PIK3CA mutation was related to older age, proximal tumors, mucinous histology, and KRAS mutation (P < 0.04). In integrated cohort analysis, PIK3CA exon 9 and 20 mutations were overrepresented in proximal, CIMP-low (CIMP-L), and KRAS-mutated cancers (P ≤ 0.011). Comparing PIK3CA exonic mutants, exon 20 mutation was associated with MSI-H, CIMP-H, and BRAF mutation, and exon 9 mutation was associated with KRAS mutation (P ≤ 0.027). Disease-free survival for stage II/III colorectal cancers did not differ by PI3K pathway status.

CONCLUSION

PI3K pathway mutation is prominent in proximal colon cancers, with PIK3CA exon 20 and PTEN mutations associated with features of the sessile-serrated pathway (MSI-H/CIMP-H/BRAF(mut)), and PIK3CA exon 9 (and to a lesser extent exon 20) mutation associated with features of the traditional serrated pathway (CIMP-L/KRAS(mut)) of tumorigenesis. Our data highlight the PI3K pathway as a therapeutic target in distinct colorectal cancer subtypes.

Restoration of PTEN activity decreases metastases in an orthotopic model of colon cancer

BACKGROUND

Mutational loss of tumor suppressor phosphatase and tensin homologue deleted on chromosome ten (PTEN) is associated with malignant progression in many cancers, including colorectal cancer (CRC). PTEN is involved in negatively regulating the phosphatidylinositol 3-kinase/AKT oncogenic signaling pathway and has been implicated in the metastatic colonization process. Few in vivo models are available to study CRC metastasis. The purpose of this study was to determine the effect of restoring PTEN activity on metastases in an orthotopic murine model.

METHODS

Green fluorescent protein labeled TENN, a highly metastatic human colon cancer cell line with mutational loss of PTEN gene and TENN clones (with restoration of PTEN gene) tumors were orthotopically implanted onto the colons of BALB/c nude mice and allowed to develop primary and metastatic tumors. Seven weeks post-implantation, mice were euthanized and organs extracted for examination.

RESULTS

Both TENN and TENN clone cell lines demonstrated 100% primary invasion. However, compared with the parental TENN cells, which demonstrated 62% metastases to both lungs and liver, TENN clone cells showed an approximately 50% reduction in metastasis, with only 31.6% liver metastasis and no metastasis to the lungs (P = 0.02).

CONCLUSIONS

Our study shows that reactivation of PTEN tumor suppressor pathway leads to a 50% reduction in CRC metastasis without affecting primary tumor formation. Importantly, PTEN restoration also changed the organotropic homing from liver and lung metastasis to liver metastasis only. This in vivo study demonstrates that PTEN might act specifically as a metastasis suppressor and, thus, efforts to target the phosphatidylinositol 3-kinase/PTEN pathway are legitimate.