Epidermal growth factor receptor and metastatic colorectal cancer: Insights into target therapies

Growth Factors, PI3K/AKT/mTOR and MAPK Signaling Pathways in Colorectal Cancer Pathogenesis: Where Are We Now?

Colorectal cancer (CRC) is a predominant malignancy worldwide, being the fourth most common cause of mortality and morbidity. The CRC incidence in adolescents, young adults, and adult populations is increasing every year. In the pathogenesis of CRC, various factors are involved including diet, sedentary life, smoking, excessive alcohol consumption, obesity, gut microbiota, diabetes, and genetic mutations. The CRC tumor microenvironment (TME) involves the complex cooperation between tumoral cells with stroma, immune, and endothelial cells. Cytokines and several growth factors (GFs) will sustain CRC cell proliferation, survival, motility, and invasion. Epidermal growth factor receptor (EGFR), Insulin-like growth factor -1 receptor (IGF-1R), and Vascular Endothelial Growth Factor -A (VEGF-A) are overexpressed in various human cancers including CRC. The phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) and all the three major subfamilies of the mitogen-activated protein kinase (MAPK) signaling pathways may be activated by GFs and will further play key roles in CRC development. The main aim of this review is to present the CRC incidence, risk factors, pathogenesis, and the impact of GFs during its development. Moreover, the article describes the relationship between EGF, IGF, VEGF, GFs inhibitors, PI3K/AKT/mTOR-MAPK signaling pathways, and CRC.

α‑Solanine inhibits growth and metastatic potential of human colorectal cancer cells

Solanum nigrum L. (Longkui) is one the most widely used anticancer herbs in traditional Chinese medicine. α‑Solanine is an important ingredient of S. nigrum L. and has demonstrated anticancer properties in various types of cancer. However, the effects of α‑solanine on colorectal cancer remain elusive. The aim of the present study was to assess the effects of α‑solanine on human colorectal cancer cells. The results demonstrated that α‑solanine inhibited the proliferation of RKO cells in a dose‑ and time‑dependent manner. In addition, α‑solanine arrested the cell cycle at the G0/G1 phase and suppressed the expression levels of cyclin D1 and cyclin‑dependent kinase 2 in RKO cells. α‑Solanine induced apoptosis of RKO cells, as indicated by morphological changes and positive Annexin‑FITC/propidium iodide staining. Additionally, α‑solanine activated caspase‑3, ‑8 and ‑9 in RKO cells, which contributed to α‑solanine‑induced apoptosis. α‑Solanine also increased the generation of reactive oxygen species, which contributed to caspase activation and induction of apoptosis. α‑Solanine inhibited the migration, invasion and adhesion of RKO cells, as well as the expression levels and activity of matrix metalloproteinase (MMP)‑2 and MMP‑9. In addition, α‑solanine inhibited cell proliferation, activated caspase‑3, ‑8 and ‑9, induced apoptosis, and inhibited the migration and invasion of HCT‑116 cells. Furthermore, α‑solanine inhibited tumor growth and induced apoptosis in vivo. These findings demonstrated that α‑solanine effectively suppressed the growth and metastatic potential of human colorectal cancer.

New Trends in the Therapeutic Approach to Metastatic Colorectal Cancer

Important developments in chemotherapy for metastatic colorectal cancer over the last years are reviewed, with an emphasis on the most recently published data from clinical trials. The systematic review of current literature was conducted involving Pubmed Central^® research and full articles were obtained and analyzed when appropriate. Fluorouracil still constitutes the backbone of metastatic colorectal cancer treatment; fluorouracil combination plus either irinotecan (FOLFIRI), oxaliplatin (FOLFOX) or capecitabine (CAPOX or XELOX) are chemotherapy protocols established as treatments producing similar outcomes. Actual treatment involves these chemotherapy protocols in combination with new molecular targeted drugs: bevacizumab and aflibercept (anti-vascular endothelial growth factor monoclonal antibody) and cetuximab and panitumumab (anti-epidermal growth factor receptor monoclonal antibody for patients with wild type KRAS) which confer significant survival benefits in select patients as first- or second-line therapies. The factors affecting the decisions for one treatment over other are related to the patient and toxicity drug. Finally, metastatic colorectal cancer patients progressing after all standard therapies (maintaining a good ECOG performance status) could be candidates for further therapies such as regorafenib and TAS-102. Regarding the future, promising therapies are under development for the metastatic colorectal cancer treatment and several agents are currently being evaluated in different clinical trials.

Global-scale profiling of differential expressed lysine acetylated proteins in colorectal cancer tumors and paired liver metastases

Lysine acetylated modification was indicated to impact colorectal cancer (CRC)'s distant metastasis. However, the global acetylated proteins in CRC and the differential expressed acetylated proteins and acetylated sites between CRC primary and distant metastatic tumor remains unclear. Our aim was to construct a complete atlas of acetylome in CRC and paired liver metastases. Combining high affinity enrichment of acetylated peptides with high sensitive mass spectrometry, we identified 603 acetylation sites from 316 proteins, among which 462 acetylation sites corresponding to 243 proteins were quantified. We further classified them into groups according to cell component, molecular function and biological process and analyzed the metabolic pathways, domain structures and protein interaction networks. Finally, we evaluated the differentially expressed lysine acetylation sites and revealed that 31 acetylated sites of 22 proteins were downregulated in CRC liver metastases compared to that in primary CRC while 40 acetylated sites of 32 proteins were upregulated, of which HIST2H3AK19Ac and H2BLK121Ac were the acetylated histones most changed, while TPM2 K152Ac and ADH1B K331Ac were the acetylated non-histones most altered. These results provide an expanded understanding of acetylome in CRC and its distant metastasis, and might prove applicable in the molecular targeted therapy of metastatic CRC.

BIOLOGICAL SIGNIFICANCE

This study described provides, for the first time, that full-scale profiling of lysine acetylated proteins were identified and quantified in colorectal cancer (CRC) and paired liver metastases. The novelty of the study is that we constructed a complete atlas of acetylome in CRC and paired liver metastases. Moreover, we analyzed these differentially expressed acetylated proteins in cell component, molecular function and biological process. In addition, metabolic pathways, domain structures and protein interaction networks of acetylated proteins were also investigated. Our approaches shows that of the differentially expressed proteins, HIST2H3AK19Ac and H2BLK121Ac were the acetylated histones most changed, while TPM2 K152Ac and ADH1B K331Ac were the acetylated non-histones most altered. Our findings provide an expanded understanding of acetylome in CRC and its distant metastasis, and might prove applicable in the molecular targeted therapy of metastatic CRC.

[New drugs in oncology]

BACKGROUND

Drug development in oncology has seen major innovations in recent years. Based on the molecular changes found in malignant tumors, new drugs are being developed which specifically target these altered signaling pathways.

RESULTS

In addition to the already broadly used inhibitors of growth factor and angiogenic signaling pathways, new and innovative target structures have been identified. Cancer stem cells which are thought to be the reason for drug resistance and tumor recurrence are now being targeted. c-MET signaling has emerged as an important new signaling module which can be influenced pharmacologically. Inhibitors of immune checkpoints like antibodies which target the CTLA4 molecule are leading to impressive results in clinical trials. Drugs which influence the epigenetic changes found in tumor cells are tested specifically for their ability to overcome drug resistance. Finally, treatment with oncolytic viruses has made a comeback in certain tumor entities.

CONCLUSION

Oncological treatments will see a significant addition of new drugs and treatment options in the next few years which will hopefully improve the survival of patients with tumors.

IgE-based Immunotherapy of Cancer -A Comparative Oncology Approach

Antibody-based immunotherapies are important therapy options in human oncology. Although human humoral specific immunity is constituted of five different immunoglobulin classes, currently only IgG-based immunotherapies have proceeded to clinical application.

This review, however, discusses the benefits and difficulties of IgE-based immunotherapy of cancer, with special emphasis on how to translate promising preclinical results into clinical studies. Pursuing the “Comparative Oncology” approach, novel drug candidates are investigated in clinical trials with veterinary cancer patients, most often dogs. By this strategy drug development could be speeded up, animal experiments could be reduced and novel therapy options could be introduced benefitting humans as well as man’s best friend.