BackgroundGene amplification is a frequent manifestation of genomic instability that plays a role in tumour progression and development of drug resistance. It is manifested cytogenetically as extrachromosomal double minutes (DMs) or intrachromosomal homogeneously staining regions (HSRs). To better understand the molecular mechanism by which HSRs and DMs are formed and how they relate to the development of methotrexate (MTX) resistance, we used two model systems of MTX-resistant HT-29 colon cancer cell lines harbouring amplified DHFR primarily in (i) HSRs and (ii) DMs.ResultsIn DM-containing cells, we found increased expression of non-homologous end joining (NHEJ) proteins. Depletion or inhibition of DNA-PKcs, a key NHEJ protein, caused decreased DHFR amplification, disappearance of DMs, increased formation of micronuclei or nuclear buds, which correlated with the elimination of DHFR, and increased sensitivity to MTX. These findings indicate for the first time that NHEJ plays a specific role in DM formation, and that increased MTX sensitivity of DM-containing cells depleted of DNA-PKcs results from DHFR elimination. Conversely, in HSR-containing cells, we found no significant change in the expression of NHEJ proteins. Depletion of DNA-PKcs had no effect on DHFR amplification and resulted in only a modest increase in sensitivity to MTX. Interestingly, both DM-containing and HSR-containing cells exhibited decreased proliferation upon DNA-PKcs depletion.ConclusionsWe demonstrate a novel specific role for NHEJ in the formation of DMs, but not HSRs, in MTX-resistant cells, and that NHEJ may be targeted for the treatment of MTX-resistant colon cancer.

ING4, a new member of the ING (inhibitor of growth) family of tumour suppressor genes, has been found to be deleted or down-regulated in gliomas, breast tumours, and head and neck squamous cell carcinomas. The goal of the present study was to investigate whether the expression and alternative splicing of ING4 transcripts are involved in the initiation and progression of stomach adenocarcinoma. ING4 mRNA and protein expression was examined in gastric adenocarcinoma tissues and human gastric adenocarcinoma cell lines by RT-PCR, real-time RT-PCR, tissue microarray immunohistochemistry, and western blot analysis. Alterations in ING4 transcripts were determined through sequence analysis of ING4 cDNA. Our data showed that ING4 mRNA and protein were dramatically reduced in stomach adenocarcinoma cell lines and tissues, and significantly less in female than in male patients. We also found that reduced ING4 mRNA expression correlated with the stage of the tumour. Interestingly, by sequence analysis, we discovered five novel aberrantly spliced variant forms of ING4_v1 and ING4_v2. These variants cause a codon frame-shift and, eventually, deletion of the NLS or PHD domain contributing to the mislocalization of p53 and/or HAT/HDAC complexes and, subsequently, altered gene expression in gastric adenocarcinoma. These results suggest that attenuated and aberrant ING4 expression may be involved in the initiation and progression of stomach adenocarcinoma.

BackgroundThe signal transducers and activators of transcription 3 (STAT3) signaling pathway plays important roles in oncogenesis, angiogenesis, immunity, and tumor cell invasion. In the present study, we investigated the association of interleukin (IL)-6/STAT3 signaling pathway with T lymphocytes and clinical implication in patients with gastric cancer.MethodsSeventy one patients who underwent gastrectomy due to gastric adenocarcinoma were studied. Blood samples were collected before and after surgical gastrectomy to quantify the levels of IL-6, IL-10 and VEGF using an enzyme-linked immunosorbent assay, as well as T lymphocyte subsets (CD3+, CD4+, CD8+, CD4+/CD8+) and natural killer (NK) cells by a flow cytometry. Furthermore, the expression of IL-6, survivin, STAT3, STAT3 phosphorylation (p-STAT3), and VEGF were determined in human gastric cancer and adjacent normal mucosa through Western blot and immunohistochemistry.ResultsPostoperative levels of IL-6, IL-10 and VEGF in serum were significantly lower than preoperative levels. Percentages of T-cell subsets and NK cells in blood were significantly increased after postoperative-week 1 as compared to preoperative group, which was further augmented at 1 month after gastrectomy. In addition, the expression of IL-6, survivin, STAT3, p-STAT3, and VEGF were increased in human gastric cancer tissues as compared to adjacent normal mucosa. Their expression was associated with TNM stage of gastric cancer. The level of STAT3 activation in clinical samples was correlated with IL-6 expression. All gastric tumor samples, which expressed p-STAT3, also expressed IL-6 with weak expression detected in adjacent normal mucosa.ConclusionIncreased IL-6-induced activation of STAT3 was observed in neoplastic gastric tissue, which positively correlated with tumor progression. Moreover, IL-6 and STAT3 downstream signals such as IL-10 and VEGF were reduced in patients after removal of gastric cancer as compared to pre-operation. Therefore, inhibition of the IL-6/STAT3 signaling pathway may provide a new therapeutic strategy against gastric cancer.

Colorectal cancer (CRC) is the third most common cancer in the world and distant metastasis is the leading cause of death among CRC patients. However, the underlying mechanisms of distant metastasis remain largely unknown. Amplification of 8q24 is a common chromosomal abnormality in CRC. In the present study, a putative oncogene at 8q24, TRIB1, was characterized for its role in CRC metastasis and underlying molecular mechanisms. Higher expression of TRIB1 protein was detected in 58/83 (69.9%) of CRC tissues, compared with adjacent non-tumor tissues. Moreover, the expression of TRIB1 was significantly associated with distant metastasis (P=0.043) and advanced staging (P=0.008) in CRC tissues. TRIB1 overexpression was also correlated with poor prognosis in CRC patients as analyzed in PrognoScan database. In addition, elevated expression of TRIB1 promoted CRC cell motility and adhesive ability, while silencing of TRIB1 reduced those effects. Further study revealed that TRIB1-mediated migration and invasion of CRC cells required up-regulation of MMP-2 through the activation of FAK/Src and ERK pathway. Collectively, the results suggest that TRIB1 promotes CRC cell motility by activation MMP-2 via the FAK/Src and ERK pathways. It may provide a potential diagnostic and therapeutic target for CRC.

Double minute chromosomes are cytogenetic manifestations of gene amplification frequently seen in cancer cells. Genes amplified on double minute chromosomes include oncogenes and multi-drug resistant genes. These genes encode proteins which contribute to cancer formation, cancer progression, and development of resistance to drugs used in cancer treatment. Elimination of double minute chromosomes, and therefore genes amplified on them, is an effective way to decrease the malignancy of cancer cells. We investigated the effectiveness of a cancer drug, gemcitabine, on the loss of double minute chromosomes from the ovarian cancer cell line UACC-1598. Gemcitabine is able to decrease the number of double minute chromosomes in cells at a 7500X lower concentration than the commonly used cancer drug hydroxyurea. Amplified genes present on the double minute chromosomes are decreased at the DNA level upon gemcitabine treatment. Gemcitabine, even at a low nanomolar concentration, is able to cause DNA damage. The selective incorporation of double minutes chromatin and γ-H2AX signals into micronuclei provides a strong link between DNA damage and the loss of double minute chromosomes from gemcitabine treated cells. Cells treated with gemcitabine also showed decreased cell growth, colony formation, and invasion. Together, our results suggest that gemcitabine is effective in decreasing double minute chromosomes and this affects the biology of ovarian cancer cells.

Resistance to anoikis is a characteristic of malignant cells with increased tumorigenesis and metastasis. Altered FAK activity has been strongly implicated in the development, growth, progression, and metastasis of human cancers, but the mechanism of FAK in regulating anoikis is unknown. In this study, the resistance anoikis role of FAK and its downstream mediators was evaluated in the human lung cancer cell line A549. It has been shown that down regulation of FAK stimulates the apoptosis of cells and the down-regulation of p-ERK, p-PI3K, p-Src, and p-p38. Furthermore, in detached A549 cells, increased FAK phosphorylations (Tyr397, Tyr861, Tyr925) were detected in a time-dependent manner, and the specific inhibitors of MEK1, PI3K, and Src (PD98059, LY294002, and PP2) partly abolished the resistance to the anoikis characteristic of cancer cells. Altogether, our data suggested that Src is involved in the progress of detachment-induced FAK activation in lung tumor cells. PI3K/AKT, MAPK-ERK, and perhaps MAPK-p38 but not MAPK-JNK, appear to be the key downstream effectors of FAK in mediating cell survival. The increased FAK activity upon cell detachment may contribute to the metastasis potential of malignant tumors.

Gene amplification, which involves the two major topographical structures double minutes (DMs) and homegeneously stained region (HSR), is a common mechanism of treatment resistance in cancer and is initiated by DNA double-strand breaks. NHEJ, one of DSB repair pathways, is involved in gene amplification as we demonstrated previously. However, the involvement of homologous recombination, another DSB repair pathway, in gene amplification remains to be explored. To better understand the association between HR and gene amplification, we detected HR activity in DM- and HSR-containing MTX-resistant HT-29 colon cancer cells. In DM-containing MTX-resistant cells, we found increased homologous recombination activity compared with that in MTX-sensitive cells. Therefore, we suppressed HR activity by silencing BRCA1, the key player in the HR pathway. The attenuation of HR activity decreased the numbers of DMs and DM-form amplified gene copies and increased the exclusion of micronuclei and nuclear buds that contained DM-form amplification; these changes were accompanied by cell cycle acceleration and increased MTX sensitivity. In contrast, BRCA1 silencing did not influence the number of amplified genes and MTX sensitivity in HSR-containing MTX-resistant cells. In conclusion, our results suggest that the HR pathway plays different roles in extrachromosomal and intrachromosomal gene amplification and may be a new target to improve chemotherapeutic outcome by decreasing extrachromosomal amplification in cancer.

In order to realize high contrast imaging with portable devices for potential mobile healthcare, we demonstrate a hand-held smartphone based quantitative phase microscope using the transport of intensity equation method. With a cost-effective illumination source and compact microscope system, multi-focal images of samples can be captured by the smartphone's camera via manual focusing. Phase retrieval is performed using a self-developed Android application, which calculates sample phases from multi-plane intensities via solving the Poisson equation. We test the portable microscope using a random phase plate with known phases, and to further demonstrate its performance, a red blood cell smear, a Pap smear and monocot root and broad bean epidermis sections are also successfully imaged. Considering its advantages as an accurate, high-contrast, cost-effective and field-portable device, the smartphone based hand-held quantitative phase microscope is a promising tool which can be adopted in the future in remote healthcare and medical diagnosis.