Clinical response to chemotherapy in oesophageal adenocarcinoma patients is linked to defects in mitochondria.

Chemotherapeutic drugs kill cancer cells, but it is unclear why this happens in responding patients but not in non-responders. Proteomic profiles of patients with oesophageal adenocarcinoma may be helpful in predicting response and selecting more effective treatment strategies. In this study, pretherapeutic oesophageal adenocarcinoma biopsies were analysed for proteomic changes associated with response to chemotherapy by MALDI imaging mass spectrometry. Resulting candidate proteins were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and investigated for functional relevance in vitro. Clinical impact was validated in pretherapeutic biopsies from an independent patient cohort. Studies on the incidence of these defects in other solid tumours were included. We discovered that clinical response to cisplatin correlated with pre-existing defects in the mitochondrial respiratory chain complexes of cancer cells, caused by loss of specific cytochrome c oxidase (COX) subunits. Knockdown of a COX protein altered chemosensitivity in vitro, increasing the propensity of cancer cells to undergo cell death following cisplatin treatment. In an independent validation, patients with reduced COX protein expression prior to treatment exhibited favourable clinical outcomes to chemotherapy, whereas tumours with unchanged COX expression were chemoresistant. In conclusion, previously undiscovered pre-existing defects in mitochondrial respiratory complexes cause cancer cells to become chemosensitive: mitochondrial defects lower the cells' threshold for undergoing cell death in response to cisplatin. By contrast, cancer cells with intact mitochondrial respiratory complexes are chemoresistant and have a high threshold for cisplatin-induced cell death. This connection between mitochondrial respiration and chemosensitivity is relevant to anticancer therapeutics that target the mitochondrial electron transport chain.

The impact of cysteine-rich intestinal protein 1 (CRIP1) in human breast cancer.

BACKGROUND: CRIP1 (cysteine-rich intestinal protein 1) has been found in several tumor types, its prognostic impact and its role in cellular processes, particularly in breast cancer, are still unclear. METHODS: To elucidate the prognostic impact of CRIP1, we analyzed tissues from 113 primary invasive ductal breast carcinomas using immunohistochemistry. For the functional characterization of CRIP1, its endogenous expression was transiently downregulated in T47D and BT474 breast cancer cells and the effects analyzed by immunoblotting, WST-1 proliferation assay and invasion assay. RESULTS: We found a significant correlation between CRIP1 and HER2 (human epidermal growth factor receptor 2) expression levels (p = 0.016) in tumor tissues. In Kaplan Meier analyses, CRIP1 expression was significantly associated with the distant metastases-free survival of patients, revealing a better prognosis for high CRIP1 expression (p = 0.039). Moreover, in multivariate survival analyses, the expression of CRIP1 was an independent negative prognostic factor, along with the positive prognosticators nodal status and tumor size (p = 0.029). CRIP1 knockdown in the T47D and BT474 breast cancer cell lines led to the increased phosphorylation of MAPK and Akt, to the reduced phosphorylation of cdc2, and to a significantly elevated cell proliferation in vitro (p < 0.001). These results indicate that reduced CRIP1 levels may increase cell proliferation and activate cell growth. In addition, CRIP1 knockdown increased cell invasion in vitro. CONCLUSIONS: Because the lack of CRIP1 expression in breast cancer tissue is significantly associated with a worse prognosis for patients and low endogenous CRIP1 levels in vitro increased the malignant potential of breast cancer cells, we hypothesize that CRIP1 may act as a tumor suppressor in proliferation and invasion processes. Therefore, CRIP1 may be an independent prognostic marker with significant predictive power for use in breast cancer therapy.

Effects of simultaneous knockdown of HER2 and PTK6 on malignancy and tumor progression in human breast cancer cells.

Breast cancer is the most common malignancy in women of the Western world. One prominent feature of breast cancer is the co- and overexpression of HER2 and protein tyrosine kinase 6 (PTK6). According to the current clinical cancer therapy guidelines, HER2-overexpressing tumors are routinely treated with trastuzumab, a humanized monoclonal antibody targeting HER2. Approximately, 30% of HER2-overexpressing breast tumors at least initially respond to the anti-HER2 therapy, but a subgroup of these tumors develops resistance shortly after the administration of trastuzumab. A PTK6-targeted therapy does not yet exist. Here, we show for the first time that the simultaneous knockdown in vitro, compared with the single knockdown of HER2 and PTK6, in particular in the trastuzumab-resistant JIMT-1 cells, leads to a significantly decreased phosphorylation of crucial signaling proteins: mitogen-activated protein kinase 1/3 (MAPK 1/3, ERK 1/2) and p38 MAPK, and (phosphatase and tensin homologue deleted on chromosome ten) PTEN that are involved in tumorigenesis. In addition, dual knockdown strongly reduced the migration and invasion of the JIMT-1 cells. Moreover, the downregulation of HER2 and PTK6 led to an induction of p27, and the dual knockdown significantly diminished cell proliferation in JIMT-1 and T47D cells. In vivo experiments showed significantly reduced levels of tumor growth following HER2 or PTK6 knockdown. Our results indicate a novel strategy also for the treatment of trastuzumab resistance in tumors. Thus, the inhibition of these two signaling proteins may lead to a more effective control of breast cancer.

Nucleic acids from long-term preserved FFPE tissues are suitable for downstream analyses.

Tissues used for clinical diagnostics are mostly formalin-fixed and paraffin-embedded (FFPE) which provides many advantages. However, the quality of the obtained nucleic acids (NA) is reduced and this turns out to be a challenge for further molecular analyses. Although the spectrum of analyses of NA extracted from FFPE tissue has increased, the standard operating procedures for NA isolation from old tissue blocks still need to be improved. Here, we compared the efficiency of different NA extraction methods, using FFPE tissues of variable age and origin, with respect to downstream analyses. Our study showed that the phenol-chloroform isoamyl alcohol (PCI) and the commercial Qiagen protocol yielded samples with highest purity. The PCI protocol delivered the longest amplicons even from samples from the 1970s. We developed a short (1 h) tissue lysis procedure that turned out to be highly time- and cost-effective when DNA quality was tested using single and multiplex PCR. Compared to a 1-day lysis-protocol, the amplicons were only 100 bp shorter. In addition, single-copy genes used in daily routine were successfully amplified from long-term stored FFPE samples following 1-h tissue-lysis. The RNA integrity numbers (RIN) determined on RNA isolated from FFPE tissues indicated degraded RNA; however, all RINs were above the generally agreed threshold of 1.4. We showed that, depending on the purpose of the analysis, NA retrieved from FFPE tissues older than 40 years may be successfully used for molecular analysis.

Radiation resistance due to high expression of miR-21 and G2/M checkpoint arrest in breast cancer cells.

BACKGROUND: There is evidence that the extent of the G2/M arrest following irradiation is correlated with tumour cell survival and hence therapeutic success. We studied the regulation of cellular response to radiation treatment by miR-21-mediated modulation of cell cycle progression in breast cancer cells and analysed miR-21 expression in breast cancer tissue samples with long-term follow up. METHODS: The miR-21 expression levels were quantified (qRT-PCR) in a panel of 86 cases of invasive breast carcinomas in relation to metastasis free survival. The cellular radiosensitivity of human breast cancer cells after irradiation was determined comparing two cell lines (T47D and MDA-MB-361) by cell proliferation and colony forming assays. The influence of miR-21 overexpression or downregulation on cell cycle progression and G2/M checkpoint arrest after irradiation was assessed by flow cytometric analysis. RESULTS: The expression of miR-21 was transiently increased 8 hours after irradiation in the radioresistant T47D cells and significantly changed with lower extent in radiosensitive MDA-MB-361 cells. Anti-miR-21 treated breast cancer cells failed to exhibit the DNA damage-G2 checkpoint increase after irradiation. Apoptotic activity was significantly enhanced from 7% to 27% in T47D cells and from 18% to 30% in MDA-MB-361 cells 24 hours after 5 Gy irradiation. Additionally, we characterized expression of miR-21 in invasive breast carcinomas. In comparison to non-cancerous adjacent breast tissue, tumours samples had increased miR-21 expression that inversely correlated with the distant metastases-free survival of patients (p = 0.029). CONCLUSIONS: Our data indicate that miR-21 expression in breast cancer cells contributes to radiation resistance by compromising cell cycle progression. These data point to the potential of combining radiotherapy with an anti-miR-21 as a potent G2/M check point inhibitor in overcoming radiation resistance of tumours.

Impact of protein tyrosine kinase 6 (PTK6) on human epidermal growth factor receptor (HER) signalling in breast cancer.

PTK6, also known as Brk, is highly expressed in over 80% of breast cancers. In the last decade several substrates and interaction partners were identified localising PTK6 downstream of HER receptors. PTK6 seems to be involved in progression of breast tumours, in particular in HER receptor signalling. Here, we show the down-regulation effects of PTK6 in the T47D, BT474 and JIMT-1 breast cancer cell lines. PTK6 knockdown leads to a decreased phosphorylation of HER2, PTEN, MAPK (ERK), p38 MAPK, STAT3 and to a reduced expression of cyclin E. Our findings show that silencing PTK6 impairs the downstream targets of HER receptors and consequently the activation of signalling molecules. Furthermore, lower levels of PTK6 result in reduced migration of T47D and JIMT-1 breast cancer cells. Due to decreased migration, the PTK6 RNA interference might contribute to reduced metastasis and malignant potential of breast cancer cells. Since PTK6 plays an important role in HER receptor signal transduction, its down-regulation might be suitable for future therapy approaches in breast cancer.