Dominance of ErbB-1 heterodimers in lung epithelial cells overexpressing ErbB-2. Both ErbB-1 and ErbB-2 contribute significantly to tumorigenicity

The ERBB3 receptor in cancer and cancer gene therapy

ERBB3, a member of the epidermal growth factor receptor (EGFR) family, is unique in that its tyrosine kinase domain is functionally defective. It is activated by neuregulins, by other ERBB and nonERBB receptors as well as by other kinases, and by novel mechanisms. Downstream it interacts prominently with the phosphoinositol 3-kinase/AKT survival/mitogenic pathway, but also with GRB, SHC, SRC, ABL, rasGAP, SYK and the transcription regulator EBP1. There are likely important but poorly understood roles for nuclear localization and for secreted isoforms. Studies of ERBB3 expression in primary cancers and of its mechanistic contributions in cultured cells have implicated it, with varying degrees of certainty, with causation or sustenance of cancers of the breast, ovary, prostate, certain brain cells, retina, melanocytes, colon, pancreas, stomach, oral cavity and lung. Recent results link high ERBB3 activity with escape from therapy targeting other ERBBs in lung and breast cancers. Thus a wide and centrally important role for ERBB3 in cancer is becoming increasingly apparent. Several approaches for targeting ERBB3 in cancers have been tested or proposed. Small inhibitory RNA (siRNA) to ERBB3 or AKT is showing promise as a therapeutic approach to treatment of lung adenocarcinoma.

Specificity and heregulin regulation of Ebp1 (ErbB3 binding protein 1) mediated repression of androgen receptor signalling

Although ErbB receptors have been implicated in the progression of prostate cancer, little is known about proteins that may mediate their interactions with the androgen receptor (AR). Ebp1, a protein cloned via its association with the ErbB3 receptor, binds the AR and inhibits androgen-regulated transactivation of wild-type AR in COS cells. As the complement of coregulators in different cells are important for AR activity, we determined the effect of Ebp1 on AR function in prostate cancer cell lines. In addition, we examined the regulation of Ebp1 function by the ErbB3/4 ligand heregulin (HRG). In this study, we demonstrate, using several natural AR-regulated promoters, that Ebp1 repressed transcriptional activation of wild-type AR in prostate cancer cell lines. Downregulation of Ebp1 expression in LNCaP cells using siRNA resulted in activation of AR in the absence of androgen. Ebp1 associated with ErbB3 in LNCaP cells in the absence of HRG, but HRG induced the dissociation of Ebp1 from ErbB3. In contrast, HRG treatment enhanced both the association of Ebp1 with AR and also the ability of Ebp1 to repress AR transactivation. These studies suggest that Ebp1 is an AR corepressor whose biological activity can be regulated by the ErbB3 ligand, HRG.

Nonsmall-cell lung cancer: chemoprevention studies

Lung cancer is the leading cause of cancer-related death in the world. Tobacco is an addictive agent producing carcinogenic effects that have been extremely difficult to prevent or detect in a curable stage. Important randomized controlled studies have been published in "healthy" smokers (primary prevention); patients with early lesions, such as mucosal dysplasia/metaplasia (secondary prevention); and those who have already had definitive treatment for their first tobacco-related malignancy (tertiary prevention). To date, the results have been generally disappointing. It is critical to remember that lung cancer is usually diagnosed decades after the patient has begun or even stopped smoking. We must intervene with more effective agents or combinations of agents and do it earlier in the process of carcinogenesis. Approximately 10% of patients with lung cancer either never smoked or only were "passive" smokers due to their environment, workplace. These "never-smokers" may actually benefit from retinoids, while current smokers have not benefited from alpha-tocopherol, retinal, N-acetylcysteine, or isotretinoin. Smokers are actually harmed by the concurrent use of beta-carotene. We now have unprecedented knowledge regarding the control of cellular growth and senescence. New diagnostic tools also allow detection of smaller lesions. We must use all our knowledge of the cancer biology, new risk models, more refined intermediate markers, and modern detection tools to focus more clearly on the pathology of lung cancer and design research to ask more probing and relevant questions so we can begin to put an end to the worldwide scourge of this terrible killer.

Frequent overexpression of the c-kit protein in large cell neuroendocrine carcinoma of the lung

Overexpression of receptor-type tyrosine kinases in various cancers is associated with an aggressive tumor phenotype and poor outcome, but their expression had never been evaluated in large cell neuroendocrine carcinoma (LCNEC) of the lung. In the present study, we investigated the expression of three receptor tyrosine kinases, epidermal growth factor receptor (EGFR), c-erbB-2, and c-kit protein, by comparing surgically resected 40 LCNECs with other neuroendocrine (NE) lung tumors: 9 typical carcinoids (TCs), 5 atypical carcinoids (ACs), and 13 small cell lung carcinomas (SCLCs). None of the NE lung tumors showed expression of EFGR or c-erbB-2, but c-kit was overexpressed in 55% of the LCNEC tumor cells and 46% of the SCLC tumor cells. None of the clinicopathologic factors in either the LCNEC or SCLC patients correlated with c-kit overexpression. The finding that c-kit expression in LCNEC is similar to its expression in SCLC suggests that inhibition of c-kit may be effective as a therapy targeting LCNEC as well as SCLC.

The role of epidermal growth factor receptor in head and neck squamous cell carcinoma

Growth factor receptors play a crucial role in the cell proliferation pathways involved in the development of cancer. One such receptor, the epidermal growth factor receptor (EGFR), is upregulated in many types of human tumors, particularly head and neck squamous cell carcinoma (HNSCC). EGFR overexpression in HNSCC has been the basis for investigation of therapeutic strategies that target EGFR. EGFR-blocking methods under evaluation involve immunotoxins, monoclonal antibodies, EGFR-specific tyrosine kinase inhibitors, and antisense approaches. These molecular targeting tactics have produced a number of agents that are currently in various stages of preclinical investigation, along with clinical trials to assess their potential as anticancer treatments.

EGFR family expression in breast carcinomas. c-erbB-2 and c-erbB-4 receptors have different effects on survival

One hundred patients with breast carcinoma followed for 7-11 years were included in the present study of EGFR family members, using immunohistochemistry and RT-PCR. By immunohistochemistry, 36%, 27%, 26%, and 82% of the tumours were positive for EGFR, c-erbB-2, c-erbB-3, and c-erbB-4. All the immunoreactive tumours were confirmed positive by RT-PCR. Tumour size, histological grade, lymph node status, S-phase fraction, and stage were confirmed to be significantly associated with both disease-free and cancer-specific survival in the present study. Methods of treatment, histological type, and ploidy had no significant effect on survival. Statistical analysis of EGFR family members in these tumours showed a significant association between c-erbB-2 expression and reduced disease-free and cancer-specific survival. c-erbB-4 expression was associated with a more favourable outcome. Co-expression of c-erbB-2 and EGFR was associated with a worse prognosis. c-erbB-4 expression, however, showed an antagonistic effect on the clinical influence of c-erbB-2 expression. In conclusion, c-erbB-2 expression in breast carcinomas is associated with an unfavourable clinical course and EGFR expression has a synergistic effect. However, c-erbB-4 antagonizes the c-erbB-2 effect on clinical course in breast carcinomas. To achieve best results with immunotherapy against the c-erbB-2 receptor, clarifying the status of c-erbB-4 expression may be of significance.

Correlation between c-erbB-4 receptor expression and response to gemcitabine-cisplatin chemotherapy in non-small-cell lung cancer

BACKGROUND

While the overexpression of c-erbB gene family in several malignancies is associated with poorer prognosis, the association between the expression of the cellular markers and the response to chemotherapy is not yet clear. In this study we investigated the expression of c-erbB-4 receptor in NSCLC and correlated it with the response to gemcitabine-cisplatin combination chemotherapy.

PATIENTS AND METHODS

Forty-three NSCLC patients with histologically or cytologically proven disease were treated with gemcitabine-cisplatin combination chemotherapy. Immunohistochemical stains for c-erbB-4 receptor were performed in 20 cases on paraffin sections using the avidin-biotin-peroxidase method.

RESULTS

Two patients achieved complete response (5%), and 16 achieved partial response (37%) yielding an overall objective response rate of 42%. Minimal response was observed in seven patients (16%) and disease stabilization in 7%. Immunohistochemical stain was positive for the presence of c-erbB-4 receptor in 25% of patients, and negative in 75%. No response was documented in c-erbB-4 positive patients (0 of 5) while an objective response (complete, partial or minimal) was seen in 11 of 15 (73%) c-erbB-4 negative patients. Negative stain for c-erbB-4 significantly favored response to gemcitabine-cisplatin combination (P < 0.01).

CONCLUSION

C-erbB-4 expression status showed no correlation with survival and cannot be accepted at this time as a guiding factor for therapeutic management. These interesting results deserve further evaluation in a large-scale prospective trial before treatment recommendations on the basis of c-erbB-4 presence can be finally made.