LAMB3 mediates apoptotic, proliferative, invasive, and metastatic behaviors in pancreatic cancer by regulating the PI3K/Akt signaling pathway.

The poor prognosis of patients with pancreatic ductal adenocarcinoma (PDAC) is partially attributed to the invasive and metastatic behavior of this disease. Laminin subunit beta-3 (LAMB3) encodes one of the three subunits of LM-332, an extracellular matrix protein secreted by cultured human keratinocytes. In addition, LAMB3 is involved in the invasive and metastatic abilities of some types of cancer, including colon, pancreas, lung, cervix, stomach, and prostate cancer, but the role and mechanism of LAMB3 in PDAC have not been previously determined. Herein, we tentatively investigated the role of LAMB3 in the malignant biological behavior of PDAC. In this study, we demonstrated that LAMB3 is upregulated in PDAC. Inhibition of LAMB3 abrogated the tumorigenic outcomes of PI3K/Akt signaling pathway activation, including those involving cell cycle arrest, cell apoptosis, proliferation, invasion and migration in vitro, and tumor growth and liver metastasis in vivo. Our results showed that LAMB3 could mediate cell cycle arrest and apoptosis in PDAC cells and alter the proliferative, invasive, and metastatic behaviors of PDAC by regulating the PI3K/Akt signaling pathway. LAMB3 may be a novel therapeutic target for the treatment of PDAC in the future.

Targeting focal adhesion kinase with dominant-negative FRNK or Hsp90 inhibitor 17-DMAG suppresses tumor growth and metastasis of SiHa cervical xenografts.

Focal adhesion kinase (FAK), a nonreceptor protein tyrosine kinase and key modulator of integrin signaling, is widely expressed in different tissues and cell types. Recent evidence indicates a central function of FAK in neoplasia where the kinase contributes to cell proliferation, resistance to apoptosis and anoikis, invasiveness, and metastasis. FAK, like other signaling kinases, is dependent on the chaperone heat shock protein 90 (Hsp90) for its stability and proper function. Thus, inhibition of Hsp90 might be a way of disrupting FAK signaling and, consequently, tumor progression. FAK is expressed in high-grade squamous intraepithelial lesions and metastatic cervical carcinomas but not in nonneoplastic cervical mucosa. In SiHa, a cervical cancer cell line with characteristics of epithelial-to-mesenchymal transition, the stable expression of dominant-negative FAK-related nonkinase decreases anchorage independence and delays xenograft growth. FAK-related nonkinase as well as the Hsp90 inhibitor 17-dimethylaminoethylamino-17-demethoxygeldanamycin both negatively interfere with FAK signaling and focal adhesion turnover. Short-term 17-dimethylaminoethylamino-17-demethoxygeldanamycin treatment prolongs survival in a SiHa lung metastasis model and chronic administration suppresses tumor growth as well as metastatic spread in orthotopic xenografts. Taken together, our data suggest that FAK is of importance for tumor progression in cervical cancer and that disruption of FAK signaling by Hsp90 inhibition might be an avenue to restrain tumor growth as well as metastatic spread.

Efficacy of Hsp90 inhibition for induction of apoptosis and inhibition of growth in cervical carcinoma cells in vitro and in vivo.

PURPOSE: Heat shock protein 90 (Hsp90) is a conserved chaperone involved in crucial signaling events in normal and malignant cells. Previous research suggests that tumor cells are particularly dependent on Hsp90 for survival as well as malignant progression. Hsp90 inhibitors which are derivates of the natural compound geldanamycin, such as the orally bioavailable 17-(dimethylaminoethylamino)-17-demethoxygeldanamycin (17-DMAG), are currently being tested in clinical trials and small molecule inhibitors are in development. In this study we investigated the response of a panel of cervical carcinoma cell lines in vitro and in vivo to determine potential factors that might influence the sensitivity towards Hsp90 inhibition. METHODS: Cell viability, proliferation and drug-induced changes on Hsp90 chaperoned "client" factors were examined with focus on G2/M cell cycle regulators, and a comparison with immortalized and normal keratinocytes was performed. ME180 and CaSki cells were grown as subcutaneous xenografts in mice treated with 6-10 mg/kg 17-DMAG by oral gavage 2x/day on a chronic schedule. Tissue concentrations of 17-DMAG were measured by high performance liquid chromatography. RESULTS: Cell death during abnormal mitosis was observed within 48 h after treatment start. ME180 and CaSki showed more cell death at this time point than SiHa and HeLa, and higher levels of pre-treatment Akt activity. IC(50) values ranged between 17 and 37 nanoM geldanamycin (MTS). Keratinocytes were at least as sensitive as carcinoma cells. All cell lines responded with an increase of the G2/M fraction. Despite in vitro effectiveness and tissue concentrations of 1 microM, only a limited tumor growth reduction was observed with 17-DMAG given close to the maximum tolerated dose level. Lower levels of Hsp90 protein, a lower Akt activity and signs of tissue hypoxia were observed in xenografts compared to cell cultures. CONCLUSIONS: We show here that Hsp90 inhibition effectively induces apoptosis and growth arrest in cervical carcinoma cells in vitro. Mitotic catastrophe was identified as one mechanism of cell death. In contrast, a limited efficacy of 17-DMAG was observed in subcutaneous xenograft models. Induction of a heat shock response has previously been implicated in resistance towards Hsp90 inhibition. Additional factors might be (1) an altered abundance and/or activity of primary (Hsp90) and secondary (e.g., Akt) target(s), (2) a narrow therapeutic range of 17-DMAG by oral application and (3) response-modifying factors within the tumor environment. The further development of synthetic Hsp90 inhibitors with increased therapeutic window is warranted.