Targeting HER1/EGFR in cancer therapy: experience with erlotinib

Targeted Engineering of Medicinal Chemistry for Cancer Therapy: Recent Advances and Perspectives

Severe side effects and poor therapeutic efficacy are the main drawbacks of current anticancer drugs. These problems can be mitigated by targeting, but the targeting efficacy of current drugs is poor and urgently needs improvement. Taking this into consideration, this Review first summarizes the current targeting strategies for cancer therapy in terms of cancer tissue and organelles. Then, we analyse the systematic targeting of anticancer drugs and conclude that a typical journey for a targeted drug administered by intravenous injection is a CTIO cascade of at least four steps. Furthermore, to ensure high overall targeting efficacy, the properties of a targeting drug needed in each step are further analysed, and some guidelines for structure optimization to obtain effective targeting drugs are offered. Finally, some viewpoints highlighting the crucial problems and potential challenges of future research on targeted cancer therapy are presented. This review could actively promote the development of precision medicine against cancer.

LncZEB1-AS1 regulates hepatocellular carcinoma bone metastasis via regulation of the miR-302b-EGFR-PI3K-AKT axis

In patients with hepatocellular carcinoma (HCC), disease progression and associated bone metastasis (BM) can markedly reduce quality of life. While the long non-coding RNA (lncRNA) zinc finger E-box binding homeobox 1 antisense 1 (ZEB1-AS1) has been shown to function as a key regulator of oncogenic processes in HCC and other tumor types, whether it plays a role in controlling HCC BM remains to be established. In the current study, we detected the significant upregulation of lncZEB1-AS1 in HCC tissues, and we found this expression to be associated with BM progression. When we knocked down this lncRNA in HCC cells, we found that this significantly reduced their migratory, invasive, and metastatic activity both in vitro and in vivo. At a mechanistic level, we found that lncZEB1-AS1 was able to target miR-302b and to thereby increase PI3K-AKT pathway activation and EGFR expression, resulting in the enhanced expression of downstream matrix metalloproteinase genes in HCC cells. In summary, our results provide novel evidence that lncZEB1-AS1 can promote HCC BM through a mechanism dependent upon the activation of PI3K-AKT signaling, thus highlighting a potentially novel therapeutic avenue for the treatment of such metastatic progression in HCC patients.

Cyclooxygenase-2 mediates gefitinib resistance in non-small cell lung cancer through the EGFR/PI3K/AKT axis

Gefitinib is a potent inhibitor of EGFR and represents the front-line treatment for non-small cell lung cancer (NSCLC) therapeutics. However, NSCLC patients are prone to develop acquired resistance through as yet, undefined mechanisms of resistance. Here, we investigated the role of COX-2 during gefitinib resistance in NSCLC cells and revealed its underlying mechanism(s) of action. We report the upregulation of COX-2 in gefitinib-resistant NSCLC tissues and cells, which is associated with poor prognosis. In vitro assays in NSCLC cells (PC9/GR) showed that COX-2 facilitates gefitinib resistance in NSCLC cells through its effects on P-gp, MRP1, and BCRP, and cancer cell migration and invasion. In vivo, COX-2 silencing could repress tumor growth. We found that the overexpression of COX-2 enhances the transcription of MMP-2, MMP-7, and MMP-9 which mediates PI3K-AKT activation. In summary, we demonstrate that COX-2 mediates the gefitinib resistance of NSCLC cells through its interaction with EGFR and the PI3K-AKT axis. This highlights COX-2 as a novel molecular target for NSCLC.

Tropomodulin 3 modulates EGFR-PI3K-AKT signaling to drive hepatocellular carcinoma metastasis

The mechanism of hepatocellular carcinoma (HCC) metastasis remains poorly understood. Tropomodulin 3 (TMOD3) is a member of the pointed end capping protein family that contributes to invasion and metastasis in several types of malignancies. It has been found to be crucial for the membranous skeleton and embryonic development, although, its role in HCC progression remains largely unclear. We observed increased levels of Tmod3 in HCCs, especially in extrahepatic metastasis. High Tmod3 expression correlated with aggressive carcinoma and poor patient with HCC survival. Loss-of-function studies conducted by us determined Tmod3 as an oncogene that promoted HCC growth and metastasis. Mechanistically, Tmod3 increases transcription of matrix metalloproteinase-2, -7, and -9 which required PI3K-AKT. Interaction between Tmod3 and epidermal growth factor receptor (EGFR) that supports the activation of EGFR phosphorylation, is essential for signaling activation of PI3K-AKT viral oncogene homolog. These findings reveal that Tmod3 enhances aggressive behavior of HCC both in vitro and in vivo by interacting with EFGR and by activating the PI3K-AKT signaling pathway.

Neurotensin promotes cholangiocarcinoma metastasis via the EGFR/AKT pathway

Cholangiocarcinoma (CCA) is a fatal disease with increasing morbidity and poor prognosis due to poor response to conventional chemotherapy or radiotherapy. Neurotensin (NTS) has long been recognized as an important factor in the central nervous system and as an endocrine agent in the peripheral circulation via NTS receptor (NTSR) mediated actions. In recent years, NTS has been implicated in the carcinogenesis of numerous cancers; however, its role in cholangiocarcinoma remains obscure. Here, we observed the expression of NTS in cholangiocarcinoma vs. non-cancerous tissues and found that up-regulation of NTS facilitated cholangiocarcinoma cell metastasis and down-regulation of NTS inhibited their migration ability. Mechanistically, NTS drove cholangiocarcinoma cell metastasis via the EGFR/AKT pathway. Both the PI3-K inhibitor LY294002 or EGFR inhibitor Erlotinib stopped the discrepant metastatic capacity between NTS-depleted cholangiocarcinoma cells and control cells, further confirming that EGFR/AKT was required in NTS-promoted cholangiocarcinoma cell metastasis. More importantly, overexpression of NTS predicted poor prognosis of CCA patients. In summary, NTS could promote cholangiocarcinoma cells metastasis by amplifying EGFR/AKT signaling and may therefore be useful to predict patient prognosis.

EGFR Signaling in Liver Diseases

The epidermal growth factor receptor (EGFR) is a transmembrane receptor tyrosine kinase that is activated by several ligands leading to the activation of diverse signaling pathways controlling mainly proliferation, differentiation, and survival. The EGFR signaling axis has been shown to play a key role during liver regeneration following acute and chronic liver damage, as well as in cirrhosis and hepatocellular carcinoma (HCC) highlighting the importance of the EGFR in the development of liver diseases. Despite the frequent overexpression of EGFR in human HCC, clinical studies with EGFR inhibitors have so far shown only modest results. Interestingly, a recent study has shown that in human HCC and in mouse HCC models the EGFR is upregulated in liver macrophages where it plays a tumor-promoting function. Thus, the role of EGFR in liver diseases appears to be more complex than what anticipated. Further studies are needed to improve the molecular understanding of the cell-specific signaling pathways that control disease development and progression to be able to develop better therapies targeting major components of the EGFR signaling network in selected cell types. In this review, we compiled the current knowledge of EGFR signaling in different models of liver damage and diseases, mainly derived from the analysis of HCC cell lines and genetically engineered mouse models (GEMMs).

CKAP4 inhibited growth and metastasis of hepatocellular carcinoma through regulating EGFR signaling

CKAP4, one kind of type II trans-membrane protein, plays an important role to maintain endoplasmic reticulum structure and inhibits the proliferation of bladder cancer cells by combining its ligand anti-proliferative factor (APF). However, the biological function of CKAP4 in the progression of liver cancer has not been clearly demonstrated. In the present study, we knocked down or overexpressed CKAP4 in hepatocellular carcinoma (HCC) cells and cell proliferation, invasion, and migration capacities were investigated by CCK-8 and transwell assays. In vivo tumor model in mice was used to evaluate the role of CKAP4 on growth and metastasis of HCC. The data documented that HCC cells with high CKAP4 levels were featured by low proliferation capability as well as low invasion potential. Interestingly, we found that CKAP4 suppressed the activation of epithelial growth factor receptor (EGFR) signaling, which may partly explain the role of CKAP4 in cell biological behavior of HCC. Further study revealed that CKAP4 could associate with EGFR at basal status and the complex was reduced upon EGF stimulation, leading to release EGFR into cytoplasm. Thus, we demonstrate the novel mechanism, for the first time, expression of CKAP4 regulates progression and metastasis of HCC and it may provide therapeutic values in this tumor.

MUC15 inhibits dimerization of EGFR and PI3K-AKT signaling and is associated with aggressive hepatocellular carcinomas in patients

BACKGROUND & AIMS

Aberrant expression of MUC15 correlates with development of colorectal adenocarcinoma, and MUC15 has been reported to prevent trophoblast invasion of human placenta. However, little is known about the role of MUC15 in pathogenesis of hepatocellular carcinoma (HCC).

METHODS

We analyzed HCC samples and matched nontumor liver tissues (controls) collected from 313 patients who underwent hepatectomy in Shanghai, China, from January 2006 through September 2009. Levels of messenger RNAs and proteins were determined by immunohistochemical, quantitative reverse transcription polymerase chain reaction, and immunoblot analyses. Statistical analyses were used to associate levels of MUC15 with tumor features and patient outcomes.

RESULTS

Levels of MUC15 messenger RNA and protein were reduced in a greater percentage of HCC samples than control tissues. Tumors with reduced levels of MUC15 were more likely to have aggressive characteristics (eg, high levels of α-fetoprotein, vascular invasion, lack of encapsulation, and poor differentiation) than those with low levels. Patients whose tumors had reduced levels of MUC15 had shorter overall survival times (24 months vs 46 months for patients with tumors with high levels of MUC15) and time to disease recurrence. Stable expression of MUC15 in HCC cell lines (SMMC-7721 and HCC-LM3) reduced their proliferation and invasive features in vitro, and ability to form metastatic tumors in mice. MUC15 reduced transcription of the matrix metalloproteinases 2 and 7 increased expression of tissue inhibitor of metalloproteinase-2, which required phosphoinositide 3-kinase-v-akt murine thymoma viral oncogene homolog signaling. Physical interaction between MUC15 and epidermal growth factor receptor led to its relocation and degradation within early endosomes and was required for inactivation of phosphoinositide 3-kinase-v-akt murine thymoma viral oncogene homolog signaling.

CONCLUSIONS

Reduced levels of MUC15 in HCCs are associated with shorter survival times of patients and reduced time to disease recurrence. Expression of MUC15 in HCC cells reduces their aggressive behavior in vitro and in mice by inducing dimerization of epidermal growth factor receptor and decreasing phosphoinositide 3-kinase signaling via v-akt murine thymoma viral oncogene homolog.

Crizotinib (PF-02341066) reverses multidrug resistance in cancer cells by inhibiting the function of P-glycoprotein

BACKGROUND AND PURPOSE

Besides targeting the well-known oncogenic c-Met, crizotinib is the first oral tyrosine kinase inhibitor inhibiting anaplastic lymphoma kinase (ALK) in clinical trials for the treatment of non-small cell lung cancer. Here, we assessed the possible reversal of multidrug resistance (MDR) by crizotinib in vitro and in vivo.

EXPERIMENTAL APPROACH

1-(4,5-Dimethylthiazol-2-yl)-3,5- diphenylformazan was used in vitro and xenografts in nude mice were used in vivo to investigate reversal of MDR by crizotinib. To understand the mechanisms for MDR reversal, the alterations of intracellular doxorubicin or rhodamine 123 accumulation, doxorubicin efflux, ABCB1 expression level, ATPase activity of ABCB1 and crizotinib-induced c-Met, Akt and ERK1/2 phosphorylation were examined.

KEY RESULTS

Crizotinib significantly enhanced the cytotoxicity of chemotherapeutic agents which are also ABCB1 substrates, in MDR cells with no effect found on sensitive cells in vitro and in vivo. Additionally, crizotinib significantly increased intracellular accumulation of rhodamine 123 and doxorubicin and inhibited the drug efflux in ABCB1-overexpressing MDR cells. Further studies showed that crizotinib enhanced the ATPase activity of ABCB1 in a concentration-dependent manner. However, expression of ABCB1 was not affected, and reversal of MDR by crizotinib was not related to the phosphorylation of c-Met, Akt or ERK1/2. Importantly, crizotinib significantly enhanced the effect of paclitaxel against KBv200 cell xenografts in nude mice.

CONCLUSIONS AND IMPLICATIONS

Crizotinib reversed ABCB1-mediated MDR by inhibiting ABCB1 transport function without affecting ABCB1 expression or blocking the Akt or ERK1/2 pathways. These findings are useful for planning combination chemotherapy of crizotinib with conventional chemotherapeutic drugs.

Role and relevance of TrkB mutations and expression in non-small cell lung cancer

PURPOSE

TrkB has been involved in poor cancer outcome. TrkB mutations have been reported in non-small cell lung cancer. In this study, we aimed at characterizing the role of three potentially sensitizing TrkB mutations previously reported in lung cancer.

EXPERIMENTAL DESIGN

We characterized three activation loop mutants of TrkB (M713I, R715G, and R734C) in terms of pathway activation/phosphorylation, migration, anchorage-independent growth, and sensitivity to a Trk inhibitor, using NIH3T3 cells and Baf3 cells. We also sequenced the tyrosine kinase domain of TrkB in a large number of lung cancer samples of East-Asian origin and cell lines.

RESULTS

None of the mutants were constitutively active in NIH3T3 transformation and migration assays. M713I and R734C mutants showed low levels of autophosphorylation in comparison with wild-type TrkB. Although R715G showed similar level of autophosphorylation to wild-type TrkB on brain-derived neurotrophic factor stimulation, the mutant was not as competent as wild-type TrkB in supporting interleukin-3-independent growth of Baf3 cells. In addition, the Trk inhibitor AZD6918 inhibited wild-type TrkB-induced cell migration and cell growth, whereas the mutants were relatively resistant to the Trk inhibitor compared with wild-type TrkB. We could not confirm the presence of nonsynonymous mutation in 78 lung cancer samples and 29 cell lines.

CONCLUSIONS

Wild-type, but not mutant, TrkB enhances cell migration and transformation. Our study suggests that TrkB mutations should not be used for selection of patients with lung cancer treated with Trk inhibitors. High expression of wild-type TrkB might be beneficial for studies of Trk inhibitors.

New molecular targets for hepatocellular carcinoma: the ErbB1 signaling system

Hepatocellular carcinoma (HCC) is a major cause of cancer-related deaths. This malignancy is often diagnosed at an advanced state, when most potentially curative therapies are of limited efficacy. In addition, HCC is a type of tumor highly resistant to available chemotherapeutic agents, which leaves HCC patients with no effective therapeutic options and a poor prognosis. From a molecular perspective, HCC is a heterogeneous type of tumor. However, in most cases, HCC emerges on a background of persistent liver injury, inflammation and hepatocellular proliferation, which is characteristic of chronic hepatitis and cirrhosis. Recent studies have revealed that dysregulation of a limited number of growth and survival-related pathways can play a key role in HCC development. The epidermal growth factor receptor (ErbB1) can be bound and activated by a broad family of ligands, and can also engage in extensive cross talk with other signaling pathways. This system is considered as an important defense mechanism for the liver during acute tissue injury; however, accumulating evidences suggest that its chronic stimulation can participate in the neoplastic conversion of the liver. Agents that target the ErbB1 receptor have shown antineoplastic activity in other types of tumors, but their efficacy either alone or in combination with other compounds has just started to be tested in experimental and human HCC. Here, we review the evidences that support the involvement of the ErbB1 in HCC development and that provide a rationale for ErbB1 targeting in HCC prevention and treatment.

Dual inhibition of ErbB1 (EGFR/HER1) and ErbB2 (HER2/neu)

Targeting of epidermal growth factor receptor (EGFR) and HER2 is a proven anti-cancer strategy. However, heterodimerisation, compensatory 'crosstalk' and redundancy exist in the ErbB network, and there is therefore a sound scientific rationale for dual inhibition of EGFR and HER2. Trials of approved agents in combination, for example trastuzumab and cetuximab, are underway. There is also a new generation of small molecule tyrosine kinase inhibitors (TKIs) and monoclonal antibodies (mABs) that target two or more ErbB receptors. Lapatinib, a TKI of EGFR and HER2, has shown clinical benefit in trastuzumab refractory breast cancer and is poised for FDA approval. Other agents include BIBW-2992 and HKI-272, irreversible TKIs of EGFR and HER2, and pertuzumab, a heterodimerisation inhibitor of EGFR and HER2.