Anti-angiogenic therapies for metastatic colorectal cancer: Current and future perspectives

ESM1 promotes angiogenesis in colorectal cancer by activating PI3K/Akt/mTOR pathway, thus accelerating tumor progression

BACKGROUND

This study aimed to explore the influence of endothelial cell-specific molecule 1 (ESM1) expression on colorectal cancer (CRC) cells and preliminarily analyze its possible mechanism, so as to lay a foundation for research about potential biological targets of CRC.

METHODS

First, CRC cells were transfected with ESM1-negative control (NC), ESM1-mimic and ESM1-inhibitor and randomly assigned to ESM1-NC group, ESM1-mimic group and ESM1-inhibitor group, respectively. Then the cells were harvested at 48 h after transfection for subsequent experiments.

RESULTS

The results manifested that after up-regulation of ESM1, the distance of CRC SW480 and SW620 cell lines migrating to the scratch center rose notably, and the number of migrating cells, basement membrane-penetrating cells, colonies formed and angiogenesis was increased overtly, indicating that ESM1 overexpression can promote tumor angiogenesis in CRC and accelerate tumor progression. Combined with results of bioinformatics analysis, the molecular mechanism by which ESM1 promoted tumor angiogenesis in CRC and accelerated tumor progression was explored through suppressing the protein expression of phosphatidylinositol 3-kinase (PI3K). Western blotting revealed that after intervention with PI3K inhibitor, the protein expressions of phosphorylated PI3K (p-PI3K), phosphorylated protein kinase B (p-Akt) and phosphorylated mammalian target of rapamycin (p-mTOR) were decreased evidently, and the protein expressions of matrix metalloproteinase-2 (MMP-2), MMP-3, MMP-9, Cyclin D1, Cyclin A2, VEGF, COX-2 and HIF-1α subsequently declined.

CONCLUSION

ESM1 may promote angiogenesis in CRC by activating the PI3K/Akt/mTOR pathway, thus accelerating tumor progression.

SRSF3 Promotes Angiogenesis in Colorectal Cancer by Splicing SRF

SRSF3, an important member of the serine/arginine-rich protein (SRp) family, is highly expressed in various tumors and plays an important role in tumor cell proliferation, migration and invasion. However, it is still unclear whether SRSF3 is involved in tumor angiogenesis. In this study, we first revealed that SRSF3 regulated the expression of numerous genes related to angiogenesis, including proangiogenic SRF. Then, we confirmed that SRSF3 was highly expressed in colorectal cancer (CRC) and was positively correlated with SRF. Mechanistic studies revealed that SRSF3 directly bound to the “CAUC” motif in exon 6 of SRF and induced the exclusion of introns. Knockdown of SRSF3 significantly reduced the secretion of VEGF from CRC cells. Conditioned medium from SRSF3-knockdown CRC cells significantly inhibited the migration, invasion and tube formation of human umbilical vein endothelial cells (HUVECs). In addition, SRF silencing inhibited angiogenesis, while SRF overexpression reversed the antiangiogenic effects of SRSF3 knockdown on tube formation. These findings indicate that SRSF3 is involved in the splicing of SRF and thereby regulates the angiogenesis of CRC, which offers novel insight into antiangiogenic therapy in CRC.

The roles of miRNAs' clinical efficiencies in the colorectal cancer pathobiology: A review article

MiRNAs (microRNAs) are defined as micro directors and regulators of gene expression. Since altered miRNA expression is signified in the pathobiology of diverse cancers such as colorectal cancers (CRCs), these molecules are described as therapeutic targets, either. Manipulation of miRNAs could lead to further therapy for chemo and radio-resistant CRCs. The usage of microRNAs has indicated prominent promise in the prognosis and diagnosis of CRC, because of their unique expression pattern associated with cancer types and malignancies. Nowadays, many researchers are analyzing the correlation between miRNA polymorphisms and cancer risk. With continuous incompatibility in colorectal cancer (CRC) miRNAs expression data, it is critical to move toward the content of a "pre-laboratory" analysis to speed up efficient accuracy medicine and translational study. Pathway study for the highest expressed miRNAs- regulated target genes resulted in the identification of a considerable number of genes associated with CRC pathway including PI3K, TGFβ, and APC. In this review, we aimed to collect fruitful information about miRNAs and their potential roles in CRC, and provide a meta-analysis of the most frequently studied miRNAs in association with the disease.

Development and therapeutic potential of vasopressin synthetic analog [V4Q5]dDAVP as a novel anticancer agent

Since its discovery, arginine vasopressin (AVP) was subjected to several modifications with the aim of obtaining novel derivatives with increased potency and selectivity for biomedical use. Desmopressin (dDAVP) is a first generation synthetic analog of AVP with hemostatic and antimetastatic activity. dDAVP acts as a selective agonist of the arginine vasopressin type 2 receptor (AVPR2) present in microvascular endothelium and cancer cells. Considering its selective effects on AVPR2-expressing malignant and vascular tissue, and interesting antitumor profile, dDAVP was used as a lead compound for the development of novel peptide analogs with enhanced anticancer efficacy. After conducting different structure-activity relationship studies to determine key aminoacidic positions for its antitumor activity against AVPR2-expressing malignant cells, dDAVP was rationally modified and a wide panel of synthetic analogs with different sequence and structural modifications was assessed. As a result of this structure-based drug derivatization novel AVP analog [V⁴Q⁵]dDAVP (1-deamino-4-valine-5-glutamine-8-d-arginine vasopressin) was selected as the most active candidate and further developed. [V⁴Q⁵]dDAVP was evaluated in highly aggressive and metastatic cancer preclinical models deploying enhanced cytostatic, antimetastatic and angiostatic effects in comparison to parental peptide dDAVP. In addition, novel compound demonstrated good tolerability as evaluated in several toxicological studies, and cooperative therapeutic effects after combination with standard-of-care chemotherapy. In summary, due to its ability to inhibit growth and tumor-associated angiogenesis, as well as impairing progression of metastatic disease, AVP analogs such as novel [V⁴Q⁵]dDAVP are promising compounds for further development as coadjuvant agents for the management of advance or recurrent cancers.

Toll-like receptor 6 expression, sequence variants, and their association with colorectal cancer risk

This is the first study to examine the potential correlation of the rs3796508 and rs5743810 SNPs of the TLR6 gene in patients with colorectal cancer (CRC) in a subset of the Saudi population. TLR6 gene expression was studied by real-time PCR assaysin 10 matching normal and cancer colon tissues. TLR6 expression at the protein level was determined by immunohistochemistry. A case-control search was conductedon 115 case patients and 102 controls. All samples were genotyped with the TaqMan assay for the TLR6 gene. Odds ratios and 95% confidence interval were computed from logistic regression models after adjusting for age, sex, and tumor localization. Our findings showed a decrease in TLR6 expression (p <0.001) in colon cancer tissues when compared to normal colon tissues. Global analysis revealed no significant association between the TLR6 rs3796508 and rs5743810 and CRC in this population. However, the Val/Met genotype of rs3796508 had a significantly higher frequency in the control group than in the cases for the male group (OR= 0.095, and p= 0.03385) or the volunteers aged more than 57 years OR= 0.152; and p= 0.04069, respectively). Two non-synonymous single nucleotide polymorphisms (SNP; S249P and V327M) were common in a few patients and were predicted as damaging by SIFT and Polyphen and were further analyzed for their protein stability and function using advanced bioinformatics tools. The results suggest that TLR6 rs3796508 has a crucial role as a protective factor against colorectal cancer in the older Saudi male population.

Microsatellite instability and manifestations of angiogenesis in stage IV of sporadic colorectal carcinoma

Angiogenesis represents one of the critical mechanisms that facilitates carcinoma development. The study objective was to evaluate whether the microsatellite instability of colorectal carcinoma has impact on the angiogenesis activity in liver metastases.In a cohort of 80 randomly selected patients with stage IV colorectal carcinoma, 30% were recognized as microsatellite unstable (Microsatellite instability high-frequency (MSI-H)). The endothelial progenitor cell fraction (CD309+) was counted within the subpopulation of CD34+CD45+ cell and CD34+CD45- cells by flow cytometer. vascular endothelial growth factor (VEGF) factor levels were quantified in serum samples by enzyme-linked immunosorbent assay (ELISA). A control group consisted of 36 healthy volunteers. The relationship of genomic instability to angiogenesis activity was evaluated by multivariate analysis in comparison to the controls, adopting a P < .05 value as statistically significant.The expression of endothelial progenitor cells (EPCs) and VEGF was significantly higher in MSI-H compared to both microsatellite stability (MSS) patients and healthy controls (P < .008). Multi-parametric analysis showed microsatellite instability (OR=9.12, P < .01), metastases in both lobes (OR = 32.83, P < .001) and simultaneous metastases outside liver (OR = 8.32, P < .01), as independent factors associated with increased angiogenesis as assessed by measures of EPC and VEGF. A higher percentage of EPCs within the white blood cell fraction (total % EPCs / white blood cells (WBC)) and higher serum concentrations of VEGF were present in patients with MSI-H colorectal cancer, and not with MSS cancers (P < .001).MSI-H patients with colorectal cancer metastases are associated with the overexpression of circulating EPCs and VEGF, potentially driving angiogenesis. This should be considered in therapeutic decision-making.

Anti-colorectal cancer effects of tripolinolate A from Tripolium vulgare

Tripolinolate A (TLA) is recently identified as a new compound from a halophyte plant Tripolium vulgare and has been shown to have significant in vitro activity against the proliferation of colorectal cancer and glioma cells. This study was designed to further investigate the effects of TLA on the proliferation of human normal cells, and the apoptosis and cell cycle in colorectal cancer cells, and the growth of tumors in the colorectal cancer-bearing animals. The data obtained from this study demonstrated that: 1) TLA had much less cytotoxicity in the human normal cells than the colorectal cancer cells; 2) TLA remarkably induced apoptosis in the human colorectal cancer cells and blocked cell cycle at G₂/M phase, and 3) TLA had significant anti-colorectal cancer activity in the tumor-bearing animals.

Preclinical Efficacy of [V4 Q5 ]dDAVP, a Second Generation Vasopressin Analog, on Metastatic Spread and Tumor-Associated Angiogenesis in Colorectal Cancer

Purpose

Control of metastatic spread of colorectal cancer (CRC) remains as a major therapeutic challenge. [V4 Q5 ]dDAVP is a vasopressin peptide analog with previously reported anticancer activity against carcinoma tumors. By acting as a selective agonist of arginine vasopressin type 2 membrane receptor (AVPR2) present in endothelial and tumor cells, [V⁴Q⁵]dDAVP is able to impair tumor aggressiveness and distant spread. Our aim was to evaluate the potential therapeutic benefits of [V⁴Q⁵]dDAVP on highly aggressive CRC disease using experimental models with translational relevance.

Materials and Methods

Murine CT-26 and human Colo-205 AVPR2-expressing CRC cell lines were used to test the preclinical efficacy of [V⁴Q⁵]dDAVP, both in vitro and in vivo.

Results

In syngeneic mice surgically implanted with CT-26 cells in the spleen, sustained intravenous treatment with [V⁴Q⁵]dDAVP (0.3 µg/kg) dramatically impaired metastatic progression to liver without overt signs of toxicity, and also reduced experimental lung colonization. The compound inhibited in vivo angiogenesis driven by Colo-205 cells in athymic mice, as well as in vitro endothelial cell migration and capillary tube formation. [V⁴Q⁵]dDAVP exerted AVPR2-dependent cytostatic activity in vitro (IC₅₀ 1.08 µM) and addition to 5-fluorouracil resulted in synergistic antiproliferative effects both in CT-26 and Colo-205 cells.

Conclusion

The present preclinical study establishes for the first time the efficacy of [V⁴Q⁵]dDAVP on CRC. These encouraging results suggest that the novel second generation vasopressin analog could be used for the management of aggressive CRC as an adjuvant agent during surgery or to complement standard chemotherapy, limiting tumor angiogenesis and metastasis and thus protecting the patient from CRC recurrence.

What Will We Expect From Novel Therapies to Esophageal and Gastric Malignancies?

Esophageal cancer and gastric cancer are aggressive diseases for which treatment approaches are facing a new era. Some molecular pathways, such as VEGF, EGFR, fibroblast growth factor receptor, PIK3CA, and PARP-1, have been studied, and novel targeted drugs are presumed to be developed in the near future. From The Cancer Genome Atlas report, 80% of Epstein-Barr virus tumors and 42% of tumors with microsatellite instability have PIK3CA mutations, suggesting that this pathway could be reevaluated as a possible target for new systemic treatment of gastric cancer. Notably, higher PARP-1 expression can be found in gastric cancer, which might be related to more advanced disease and worse prognosis. In addition, PD-L1 expression, high microsatellite instability, and mismatch repair deficiency can be found in gastric cancer, thus suggesting that immunotherapy may also play a role in those patients. We discuss trends related to the potential of novel therapies for patients with esophageal and gastric cancers in the near future.

Monitoring circulating tumor DNA revealed dynamic changes in KRAS status in patients with metastatic colorectal cancer

KRAS mutated circulating tumor DNA (MctDNA) can be monitored in the blood of patients with metastatic colorectal cancer (mCRC), but dynamic changes have not been determined. Four hundred and fifty-seven plasma samples were collected prospectively from 85 mCRC patients who underwent chemotherapy. MctDNA in plasma was detected by droplet digital PCR, and the percentage of MctDNA in total circulating cell-free DNA was calculated. KRAS assessment in tumor tissues showed 29 patients with the mutant-type (MT) and 56 patients with the wild-type (WT). Twenty-three of 29 MT patients (79.3%) and 28 of 56 WT patients (50.0%) showed MctDNA. Emergence of MctDNA was recognized during treatments with various drugs. Regardless of KRAS status in tumor tissues, patients with MctDNA in blood showed poor progression-free survival with first-line treatment. Median percentage of MctDNA accounted for 10.10% in MT patients and 0.22% in WT patients. These differences between MT and WT likely affected patterns of changes in MctDNA. KRAS monitoring identified dynamic changes in MctDNA, such as continuous, intermittent, and transient changes (quick elevation and disappearance). Emergence of MctDNA involved drug resistance, except for transient changes, which were seen in WT patients and likely corresponded with the drug response. Transient changes could be involved in recovery of sensitivity to anti-EGFR antibody in WT patients. Monitoring MctDNA during various treatments showed dynamic changes in KRAS status and could provide useful information for determining treatments for patients with mCRC.

Next-generation sequencing analysis of receptor-type tyrosine kinase genes in surgically resected colon cancer: identification of gain-of-function mutations in the RET proto-oncogene

BACKGROUND

Improvement in genetic characterization of Colon Cancer (CC) patients is required to propose new potential targets, since surgical resection coupled to chemotherapy, presents several limits such as cancer recurrence and drug resistance. Targeted therapies have more efficacy and less toxicity than standard treatments. One of the most relevant cancer-specific actionable targets are receptor tyrosine kinases (RTKs) whose role in CC need to be better investigated.

METHODS

We have analysed 37 CC patients using the Ion AmpliSeq™ Comprehensive Cancer Panel (CCP). We have confirmed the somatic nature of RET variants through Sanger sequencing and assessed RET activation status and protein expression by immunofluorescence and western-blot analyses. We have used RET mutant expression vectors to evaluate the effect of selected mutations in HEK293 cells by performing proliferation, migration and clonogenic assays.

RESULTS

Among the 409 cancer-related genes included in the CCP we have focused on the RTKs. Overall, we have observed 101 different potentially damaging variants distributed across 31 RTK genes in 28 patients. The most frequently mutated RTKs were FLT4, ROS1, EPH7, ERBB2, EGFR, RET, FGFR3 and FGFR4. In particular, we have identified 4 different somatic variants in 10% of CC patients in RET proto-oncogene. Among them, we have demonstrated that the G533C variant was able to activate RET by promoting dimer formation and enhancing Y1062 phosphorylation. Moreover, we have demonstrated that RET G533C variant was able to stimulate anchorage-dependent proliferation, migration and clonogenic cell survival. Notably, the effects induced by the RET G533C variant were abolished by vandetanib.

CONCLUSIONS

The discovery of pathogenic variants across RTK genes in 75% of the CC patients under analysis, suggests a previously underestimated role for RTKs in CC development. The identification of a gain-of-function RET mutation in CC highlights the potential use of RET in targeted therapy.

Lysine-specific demethylase 1 activation by vitamin B2 attenuates efficacy of apatinib for proliferation and migration of gastric cancer cell MGC-803

B vitamins play an essential role in the biosynthesis of nucleotides, replication of DNA, supply of methyl-groups, growth and repair of cells, aberrancies of which have all been implicated in carcinogenesis. Although the potential role of vitamin B in relation to the risk of cancer, including breast, and colorectal cancer, has been investigated in several observational studies, the mechanism of action is still unclear. In this study, vitamin B2 exhibited efficient activation of LSD1 by occupying the active sites where FAD stands. Interestingly, vitamin B2 significantly downregulated expression of CD86, a sensitive surrogate biomarker of LSD1 inhibition, and showed marked activation of gastric cancer cell migration and invasion. Meanwhile, vitamin B2 induced activation of LSD1 may attenuate the proliferation inhibition, and anti-migration effects of apatinib in gastric cancer cells. These findings suggested that vitamin B supplementation may interfere with the efficacy of apatinib in patients with gastric cancer.

The YAP1/SIX2 axis is required for DDX3-mediated tumor aggressiveness and cetuximab resistance in KRAS-wild-type colorectal cancer

The mechanism underlying tumor aggressiveness and cetuximab (CTX) resistance in KRAS-wild-type (KRAS -WT) colorectal cancer remains obscure. We here provide evidence that DDX3 promoted soft agar growth and invasiveness of KRAS-WT cells, as already confirmed in KRAS-mutated cells. Mechanistically, increased KRAS expression induced ROS production, which elevated HIF-1α and YAP1 expression. Increased HIF-1α persistently promoted DDX3 expression via a KRAS/ROS/HIF-1α feedback loop. DDX3-mediated aggressiveness and CTX resistance were regulated by the YAP1/SIX2 axis in KRAS-WT cells and further confirmed in animal models. Kaplan-Meier and Cox regression analysis indicated that DDX3, KRAS, and YAP1 expression had prognostic value for OS and RFS in KRAS-WT and KRAS-mutated tumors, but SIX2 and YAP1/SIX2 were prognostic value only in KRAS-WT patients. The observation from patients seemed to support the mechanistic action of cell and animal models. We therefore suggest that combining YAP1 inhibitors with CTX may therefore suppress DDX3-mediated tumor aggressiveness and enhance CTX sensitivity in KRAS-WT colorectal cancer.

[Devastating surgical complications after aflibercept chemotherapy]

BACKGROUND

The use of a new chemotherapy as adjuvant treatment of colorectal cancer is not free of complications. Monoclonal antibodies are associated with bleeding and intestinal perforations.

OBJECTIVE

To report the case of a patient who developed a serious complication after treatment with an antiangiogenic drug for colorectal neoplasm.

CLINICAL CASE

The case is presented of a 42-year-old male operated on due to subocclusive rectal cancer with metástasis at the time of diagnosis. Sixteen months after surgery during second-line adjuvant therapy, an intestinal perforation was observed with haemorrhage and intestinal leak to retroperitoneum and left lower extremity. Despite intensive medical and surgical treatment this complication had fatal consequences.

CONCLUSIONS

Future research should be directed at obtaining biomarkers for the specific use of antiangiogenic agents in order to decrease the rate of adverse factors.

Effect of Recepteur d'Origine Nantais expression on chemosensitivity and tumor cell behavior in colorectal cancer

Recepteur d'Origine Nantais (RON) expression is known to induce oncogenic properties including tumor cell growth, survival, motility, angiogenesis and chemoresistance. In the present study, we evaluated whether RON affects chemosensitivity and oncogenic behavior of colorectal cancer cells and investigated its prognostic value in colorectal cancer. To evaluate the impact of RON on chemosensitivity and tumor cell behavior, we treated colorectal cancer cells with small interfering RNAs specific to RON. This was followed by flow cytometric analyses and migration, Matrigel invasion and endothelial tube formation assays. The expression of RON was investigated by immunohistochemistry in colorectal cancer tissues. TUNEL assay and immunohistochemical staining for CD34 and D2-40 were deployed to determine apoptosis, angiogenesis and lymphangiogenesis. RON knockdown enhanced 5-fluorouracil (FU)-induced apoptosis by upregulating the activities of caspases and expression of proapoptotic genes. Moreover, it enhanced 5-FU-induced cell cycle arrest by decreasing the expression of cyclins and cyclin‑dependent kinases and inducing that of p21. Furthermore, RON knockdown augmented the 5-FU-induced inhibition of invasion and migration of colorectal cancer cells. The β-catenin signaling cascade was blocked by RON knockdown upon 5-FU treatment. RON knockdown also decreased endothelial tube formation and expression of VEGF-A and HIF-1α and increased angiostatin expression. Furthermore, it inhibited lymphatic endothelial cell tube formation and the expression of VEGF-C and COX-2. RON expression was observed to be associated with age, tumor size, lymphovascular and perineural invasion, tumor stage, lymph node and distant metastasis, and poor survival rate. The mean microvessel density value of RON-positive tumors was significantly higher than that of RON-negative ones. These results indicate that RON is associated with tumor progression by inhibiting chemosensitivity and enhancing angiogenesis in colorectal cancer.

Genistein suppresses FLT4 and inhibits human colorectal cancer metastasis

Dietary consumption of genistein, found in soy, has been associated with a potentially protective role in colorectal cancer (CRC) development and progression. Herein we demonstrate that genistein will inhibit human CRC cell invasion and migration, that it does so at non-cytotoxic concentrations and we demonstrate this in multiple human CRC cell lines. After orthotopic implantation of human CRC tumors into mice, oral genistein did not inhibit tumor growth, but did inhibit distant metastasis formation, and was non-toxic to mice. Using a qPCR array, we screened for genistein-induced changes in gene expression, followed by Western blot confirmation, demonstrating that genistein downregulated matrix metalloproteinase 2 and Fms-Related Tyrosine Kinase 4 (FLT4; vascular endothelial growth factor receptor 3). After demonstrating that genistein suppressed neo-angiogenesis in mouse tumors, we examined FLT4 expression in primary CRC and adjacent normal colonic tissue from 60 human subjects, demonstrating that increased FLT4 significantly correlates with increased stage and decreased survival. In summary, we demonstrate for the first time that genistein inhibits human CRC metastasis at dietary, non-toxic, doses. FLT4 is identified as a marker of metastatic disease, and as a response marker for small molecule therapeutics that inhibit CRC metastasis.

Impact of KITENIN on tumor angiogenesis and lymphangiogenesis in colorectal cancer

Angiogenesis and lymphangiogenesis are involved in the dissemination of tumor cells from solid tumors to regional lymph nodes and various distant sites. KAI1 COOH-terminal interacting tetraspanin (KITENIN) contributes to tumor progression and poor clinical outcomes in various cancers including colorectal cancer. The aim of the present study was to evaluate whether KITENIN affects tumor angiogenesis and lymphangiogenesis in colorectal cancer. A KITENIN small interfering RNA vector was used to silence KITENIN expression in colorectal cancer cell lines including DLD1 and SW480 cells. To evaluate the ability of KITENIN to induce angiogenesis and lymphangiogenesis in human umbilical vein endothelial cells (HUVECs) and lymphatic endothelial cells (HLECs), we performed Matrigel invasion and tube formation assays. Immunohistochemistry was used to determine the expression of KITENIN in colorectal cancer tissues. Angiogenesis and lymphangiogenesis were evaluated by immunostaining with CD34 and D2-40 antibodies. KITENIN silencing inhibited both HUVEC invasion and tube formation in the DLD1 and SW480 cells. KITENIN silencing led to decreased expression of the angiogenic inducers vascular endothelial growth factor (VEGF)-A and hypoxia-inducible factor-1α and increased expression of the angiogenic inhibitor angiostatin. KITENIN silencing did not inhibit either HLEC invasion or tube formation in all tested cells, but it resulted in decreased expression of the lymphangiogenic inducer VEGF-C. KITENIN expression was significantly associated with tumor stage, depth of invasion, lymph node and distant metastases and poor survival. The mean microvessel density was significantly higher in the KITENIN-positive tumors than that in the KITENIN-negative tumors. However, the mean lymphatic vessel density of KITENIN-positive tumors was not significantly higher than that of the KITENIN-negative tumors. These results suggest that KITENIN promotes tumor progression by enhancing angiogenesis in colorectal cancer.

Targeted therapy: resistance and re-sensitization

The last two decades have witnessed a paradigm shift from cytotoxic drugs to targeted therapy in medical oncology and pharmaceutical innovation. Inspired by breakthroughs in molecular and cellular biology, a number of novel synthesized chemical compounds and recombinant antibodies have been developed to selectively target oncogenic signaling pathways in a broad array of tumor types. Although targeted therapeutic agents show impressive clinical efficacy and minimized adverse effects compared with traditional treatments, the challenging drug-resistant issue has also emerged to limit their benefits to cancer patients. In this regard, we aim to improve targeted therapy by presenting a systematic framework regarding the drug resistance mechanisms and alternative approaches to re-sensitize cancer cells/tissues therapeutically.

Inhibition of protein phosphatase 5 (PP5) suppresses survival and growth of colorectal cancer cells

Protein phosphatase 5 (PP5) is a unique member of the protein phosphatases family that functions in multiple signaling pathways involved in DNA damage, cell cycle control, cell growth, and apoptosis. Recent evidence indicated that PP5 may play a role in cancer progression. In this study, we aimed to examine the biological effect of PP5 on cell growth and apoptosis in human colorectal cancer (CRC). We first knocked down PP5 expression in RKO cells via a short hairpin RNA containing lentivirus system. Then, methylthiazoletetrazolium assay, colony formation assay, and flow cytometry analysis were performed. The proliferation and colony formation ability of RKO cells were remarkably suppressed in PP5-silenced groups, as compared with control groups. Moreover, downregulation of PP5 resulted in a significant G0/G1 phase cell cycle arrest and an induction of apoptosis. In all, these results demonstrated the importance of PP5 in CRC cell growth, and it might be used as a potential therapeutic target for the treatment of CRC.

Geraniol Suppresses Angiogenesis by Downregulating Vascular Endothelial Growth Factor (VEGF)/VEGFR-2 Signaling

Geraniol exerts several direct pharmacological effects on tumor cells and, thus, has been suggested as a promising anti-cancer compound. Because vascularization is a major precondition for tumor growth, we analyzed in this study the anti-angiogenic action of geraniol. In vitro, geraniol reduced the migratory activity of endothelial-like eEND2 cells. Western blot analyses further revealed that geraniol downregulates proliferating cell nuclear antigen (PCNA) and upregulates cleaved caspase-3 (Casp-3) expression in eEND2 cells. Moreover, geraniol blocked vascular endothelial growth factor (VEGF)/VEGFR-2 signal transduction, resulting in a suppression of downstream AKT and ERK signaling pathways. In addition, geraniol significantly reduced vascular sprout formation in a rat aortic ring assay. In vivo, geraniol inhibited the vascularization of CT26 tumors in dorsal skinfold chambers of BALB/c mice, which was associated with a smaller tumor size when compared to vehicle-treated controls. Immunohistochemical analyses confirmed a decreased number of Ki67-positive cells and CD31-positive microvessels with reduced VEGFR-2 expression within geraniol-treated tumors. Taken together, these findings indicate that geraniol targets multiple angiogenic mechanisms and, therefore, is an attractive candidate for the anti-angiogenic treatment of tumors.

Simultaneous inhibition of EGFR/VEGFR and cyclooxygenase-2 targets stemness-related pathways in colorectal cancer cells

Despite the demonstrated benefits of anti-EGFR/VEGF targeted therapies in metastatic colorectal cancer (mCRC), many patients initially respond, but then show evidence of disease progression. New therapeutic strategies are needed to make the action of available drugs more efficient. Our study aimed to explore whether simultaneous targeting of EGFR/VEGF and cyclooxygenase-2 (COX-2) may aid the treatment and management of mCRC patients. The dual tyrosine kinase inhibitor AEE788 and celecoxib were used to inhibit EGFR/VEGFR and COX-2, respectively, in colorectal cancer cells. COX-2 inhibition with celecoxib augmented the antitumoral and antiangiogenic efficacy of AEE788, as indicated by the inhibition of cell proliferation, induction of apoptosis and G1 cell cycle arrest, down-regulation of VEGF production by cancer cells and reduction of cell migration. These effects were related with a blockade in the EGFR/VEGFR signaling axis. Notably, the combined AEE788/celecoxib treatment prevented β-catenin nuclear accumulation in tumor cells. This effect was associated with a significant downregulation of FOXM1 protein levels and an impairment in the interaction of this transcription factor with β-catenin, which is required for its nuclear localization. Furthermore, the combined treatment also reduced the expression of the stem cell markers Oct 3/4, Nanog, Sox-2 and Snail in cancer cells, and contributed to the diminution of the CSC subpopulation, as indicated by colonosphere formation assays. In conclusion, the combined treatment of AEE788 and celecoxib not only demonstrated enhanced anti-tumoral efficacy in colorectal cancer cells, but also reduced colon CSCs subpopulation by targeting stemness-related pathways. Therefore, the simultaneous targeting of EGFR/VEGF and COX-2 may aid in blocking mCRC progression and improve the efficacy of existing therapies in colorectal cancer.

Correlation of perfusion MRI and 18F-FDG PET imaging biomarkers for monitoring regorafenib therapy in experimental colon carcinomas with immunohistochemical validation

Objectives

To investigate a multimodal, multiparametric perfusion MRI / ¹⁸F-fluoro-deoxyglucose-(¹⁸F-FDG)-PET imaging protocol for monitoring regorafenib therapy effects on experimental colorectal adenocarcinomas in rats with immunohistochemical validation.

Materials and Methods

Human colorectal adenocarcinoma xenografts (HT-29) were implanted subcutaneously in n = 17 (n = 10 therapy group; n = 7 control group) female athymic nude rats (Hsd:RH-Foxn1^rnu). Animals were imaged at baseline and after a one-week daily treatment protocol with regorafenib (10 mg/kg bodyweight) using a multimodal, multiparametric perfusion MRI/¹⁸F-FDG-PET imaging protocol. In perfusion MRI, quantitative parameters of plasma flow (PF, mL/100 mL/min), plasma volume (PV, %) and endothelial permeability-surface area product (PS, mL/100 mL/min) were calculated. In ¹⁸F-FDG-PET, tumor-to-background-ratio (TTB) was calculated. Perfusion MRI parameters were correlated with TTB and immunohistochemical assessments of tumor microvascular density (CD-31) and cell proliferation (Ki-67).

Results

Regorafenib significantly (p<0.01) suppressed PF (81.1±7.5 to 50.6±16.0 mL/100mL/min), PV (12.1±3.6 to 7.5±1.6%) and PS (13.6±3.2 to 7.9±2.3 mL/100mL/min) as well as TTB (3.4±0.6 to 1.9±1.1) between baseline and day 7. Immunohistochemistry revealed significantly (p<0.03) lower tumor microvascular density (CD-31, 7.0±2.4 vs. 16.1±5.9) and tumor cell proliferation (Ki-67, 434.0 ± 62.9 vs. 663.0 ± 98.3) in the therapy group. Perfusion MRI parameters ΔPF, ΔPV and ΔPS showed strong and significant (r = 0.67-0.78; p<0.01) correlations to the PET parameter ΔTTB and significant correlations (r = 0.57-0.67; p<0.03) to immunohistochemical Ki-67 as well as to CD-31-stainings (r = 0.49-0.55; p<0.05).

Conclusions

A multimodal, multiparametric perfusion MRI/PET imaging protocol allowed for non-invasive monitoring of regorafenib therapy effects on experimental colorectal adenocarcinomas in vivo with significant correlations between perfusion MRI parameters and ¹⁸F-FDG-PET validated by immunohistochemistry.

Colorectal carcinogenesis-update and perspectives

Colorectal cancer (CRC) is a very common malignancy in the Western World and despite advances in surgery, chemotherapy and screening, it is still the second leading cause of cancer deaths in this part of the world. Numerous factors are found important in the development of CRC including colonocyte metbolism, high risk luminal environment, inflammation, as well as lifestyle factors such as diet, tobacco, and alchohol consumption. In recent years focus has turned towards the genetics and molecular biology of CRC and several interesting and promising correlations and pathways have been discovered. The major genetic pathways of CRC are the Chromosome Instability Pathway representing the pathway of sporadic CRC through the K-ras, APC, and P53 mutations, and the Microsatellite Instability Pathway representing the pathway of hereditary non-polyposis colon cancer through mutations in mismatch repair genes. To identify early cancers, screening programs have been initiated, and the leading strategy has been the use of faecal occult blood testing followed by colonoscopy in positive cases. Regarding the treatment of colorectal cancer, significant advances have been made in the recent decade. The molecular targets of CRC include at least two important cell surface receptors: the epidermal growth factor receptor and the vascular endothelial growth factor receptor. The genetic and molecular knowledge of CRC has widen the scientific and clinical perspectives of diagnosing and treatment. However, despite significant advances in the understanding and treatment of CRC, results from targeted therapy are still not convincing. Future studies will determine the role for this new treatment modality.

E7080 (lenvatinib), a multi-targeted tyrosine kinase inhibitor, demonstrates antitumor activities against colorectal cancer xenografts

Clinical prognosis of metastasized colorectal carcinoma (CRC) is still not at desired levels and novel drugs are needed. Here, we focused on the multi-tyrosine kinase inhibitor E7080 (Lenvatinib) and assessed its therapeutic efficacy against human CRC cell lines in vitro and human CRC xenografts in vivo. The effect of E7080 on cell viability was examined on 10 human CRC cell lines and human endothelial cells (HUVEC). The inhibitory effect of E7080 on VEGF-induced angiogenesis was studied in an ex vivo mouse aortic ring angiogenesis assay. In addition, the efficacy of E7080 against xenografts derived from CRC cell lines and CRC patient resection specimens with mutated KRAS was investigated in vivo. A relatively low cytotoxic effect of E7080 on CRC cell viability was observed in vitro. Endothelial cells (HUVEC) were more susceptible to the incubation with E7080. This is in line with the observation that E7080 demonstrated an anti-angiogenic effect in a three-dimensional ex vivo mouse aortic ring angiogenesis assay. E7080 effectively disrupted CRC cell-mediated VEGF-stimulated growth of HUVEC in vitro. Daily in vivo treatment with E7080 (5 mg/kg) significantly delayed the growth of KRAS mutated CRC xenografts with decreased density of tumor-associated vessel formations and without tumor regression. This observation is in line with results that E7080 did not significantly reduce the number of Ki67-positive cells in CRC xenografts. The results suggest antiangiogenic activity of E7080 at a dosage that was well tolerated by nude mice. E7080 may provide therapeutic benefits in the treatment of CRC with mutated KRAS.