piRNA, the new non-coding RNA, is aberrantly expressed in human cancer cells

BACKGROUND

Piwi-interacting RNAs (piRNAs) are a novel class of non-coding single strand RNAs. They are involved in germline development, in silencing of selfish DNA elements, and in maintaining germline DNA integrity. The relationship between piRNAs and carcinogenesis has not been shown yet.

METHODS

The relationship between piRNAs and carcinogenesis was identified by microarray screening and real-time quantitative reverse transcription-polymerase chain reaction technology. The piR-651 inhibitor was transfected into gastric cancer cells to assess its influence on cell growth. Cell cycle analysis was used to reveal the cellular mechanisms of piR-651 in the genesis of gastric cancer.

RESULTS

piR-651 expression was upregulated in gastric cancer tissues compared with paired non-cancerous tissues. The levels of piR-651 were associated with TNM stage (P=0.032). The expression of piR-651 in gastric, colon, lung, and breast cancer tissues was higher than that in paired non-cancerous tissues. The upregulated expression of piR-651 was confirmed in several cancer cell lines including gastric, lung, mesothelium, breast, liver, and cervical cancer cell lines. The growth of gastric cancer cells was inhibited by a piR-651 inhibitor and arrested at the G(2)/M phase.

CONCLUSION

piR-651 might be involved in the development of gastric cancer and other cancers, and is a potential marker for cancer diagnosis.

Non-coding RNAs and gastric cancer

Non-coding RNAs (ncRNAs) play key roles in development, proliferation, differentiation and apoptosis. Altered ncRNA expression is associated with gastric cancer occurrence, invasion, and metastasis. Moreover, aberrant expression of microRNAs (miRNAs) is significantly related to gastric cancer tumor stage, size, differentiation and metastasis. MiRNAs interrupt cellular signaling pathways, inhibit the activity of tumor suppressor genes, and affect the cell cycle in gastric cancer cells. Some miRNAs, including miR-21, miR-106a and miR-421, could be potential markers for the diagnosis of gastric cancer. Long non-coding RNAs (lncRNAs), a new research hotspot among cancer-associated ncRNAs, play important roles in epigenetic, transcriptional and post-transcriptional regulation. Several gastric cancer-associated lncRNAs, such as CCAT1, GACAT1, H19, and SUMO1P3, have been explored. In addition, Piwi-interacting RNAs, another type of small ncRNA that is recognized by gastroenterologists, are involved in gastric carcinogenesis, and piR-651/823 represents an efficient diagnostic biomarker of gastric cancer that can be detected in the blood and gastric juice. Small interfering RNAs also function in post-transcriptional regulation in gastric cancer and might be useful in gastric cancer treatment.

Detection of circulating tumor cells in peripheral blood from patients with gastric cancer using microRNA as a marker

Recently, the detection of occult cancer cells in peripheral blood has received a great deal of attention regarding the prediction of postoperative cancer recurrence and for novel strategies of adjuvant therapy. The aim of this study was to establish a new molecular diagnostic method of detecting circulating tumor cells. Gastric cancer SGC-7901 cells in 2 ml blood from healthy volunteers were serially diluted. Additional peripheral blood samples were collected from 90 patients and 27 healthy volunteers. Real-time reverse transcription-polymerase chain reaction was used to detect the levels of microRNA-106a (miR-106a) and microRNA-17 (miR-17). Receiver operating characteristics (ROC) curves were constructed. In recovery experiments, a significant correlation between the number of cancer cells and the levels of both miR-106a (r = -0.906, p = 0.037) and miR-17 (r = -0.912, p = 0.031) was found. In preoperative and postoperative patient groups, miR-106a and miR-17 levels were significantly higher than those in controls. The areas under the ROC curve for miR-106a, miR-17, and combination were 0.684 (p = 0.0066), 0.743 (p = 0.0001), and 0.741 (p = 0.0002), respectively. Our results indicate that the detection of miRNA in peripheral blood may be a novel tool for monitoring circulating tumor cells in patients with gastric cancers.

Biphasic effect of daidzein on cell growth of human colon cancer cells

Colorectal cancer is one of the most common cancers in the world, poorly responding to available chemotherapeutic agents. To investigate whether natural molecules can inhibit colon cancer progression, we investigated a principle phytoestrogen found in soybean known as daidzein, and determined its effects on the human colon cancer cell line LoVo. LoVo cells were treated with 0.1, 1, 5, 10, 50 and 100 microM daidzein for 2, 3, 4 or 5 d. The results indicated that daidzein stimulated the growth of LoVo cells at 0.1 and 1 microM whereas at higher concentrations (10, 50 and 100 microM) cell growth was inhibited in a dose-dependent manner. Treatment of daidzein at 10, 50 and 100 microM resulted in cell cycle arrest at G0/G1 phase, DNA fragmentation and increases in caspase-3 activity. There were no changes in alkaline phosphatase activity (ALP), an indicator of cell differentiation, upon treatment with daidzein when compared to controls. These results indicate that daidzein has a biphasic effect on LoVo cell growth and its tumor suppressive effect is by means of cell cycle arrest and apoptosis but not through cell differentiation.

Effects of daidzein on estrogen-receptor-positive and negative pancreatic cancer cells in vitro

AIM: To study the effects of daidzein on human pancreatic cancer cells in vitro.

METHODS: Human estrogen-receptor (ER)-positive pancreatic cancer cells MiaPaCa-2 and ER-negative pancreatic cancer cells PANC-1 were treated by 0.1 μmol/L, 1 μmol/L, 10 μmol/L, 25 μmol/L, 50 μmol/L, 75 μmol/L and 100 μmol/L of daidzein, respectively. Its antiproliferative effect was studied by MTT assay.

RESULTS: Daidzein inhibited the growth of MiaPaCa-2 and PANC-1 cells at the concentrations from 0.1 μmol/L to 100 μmol/L. A dose- and time-dependent manner was found. The IC₅₀ of daidzein on MiaPaCa-2 and PANC-1 cells was 45 μmol/L and 75 μmol/L, respectively. After MiaPaCa-2 cells were treated by daidzein for 3 d and at the concentrations more than IC₅₀, the inhibitory manner was identical and the inhibition appeared a saturation phenomenon, but the inhibitory manner of daidzein on PANC-1 cells was different from that of MiaPaCa-2 cells.

CONCLUSION: Daidzein has antiproliferative effects on human estrogen-receptor-positive and negative pancreatic cancer cells, but their mechanisms may be different.

Effect of daidzein on cell growth, cell cycle, and telomerase activity of human cervical cancer in vitro

Phytoestrogens are some plant compounds exhibiting estrogen-like activities. However, some studies have shown that they also affect the growth of some nonhormone-dependent diseases. In this study, daidzein--one of the most common phytoestrogens--was used to investigate its effects on human cervical cancer cells HeLa in vitro. First, the cell growth was measured by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Then, the distributions of cell cycle and apoptosis were analyzed with the help of flow cytometry. Finally, the telomerase activity was detected by using real-time quantitative reverse transcription-polymerase chain reaction. The results showed that at the concentrations from 6.25 to 100 micro mol/l, daidzein inhibited the growth of HeLa cells. Flow cytometric analysis showed that cancer cells were arrested at G(0)/G(1) or G(2)/M phase with daidzein. The inductive effects of apoptosis were more obviously observed in low-concentration groups. After HeLa cells were treated with daidzein, the expression of human telomerase catalytic subunit mRNA decreased. These meant that daidzein affected human nonhormone-dependent cervical cancer cells in several ways, including cell growth, cell cycle, and telomerase activity in vitro.

Growth inhibitory effect of 4-phenyl butyric acid on human gastric cancer cells is associated with cell cycle arrest

AIM: To investigate the growth effects of 4-phenyl butyric acid (PBA) on human gastric carcinoma cells and their mechanisms.

METHODS: Moderately-differentiated human gastric carcinoma SGC-7901 and lowly-differentiated MGC-803 cells were treated with 5, 10, 20, 40, and 60 μmol/L PBA for 1-4 d. Cell proliferation was detected using the MTT colorimetric assay. Cell cycle distributions were examined using flow cytometry.

RESULTS: The proliferation of gastric carcinoma cells was inhibited by PBA in a dose- and time-dependent fashion. Flow cytometry showed that SGC-7901 cells treated with low concentrations of PBA were arrested at the G₀/G₁ phase, whereas cells treated with high concentrations of PBA were arrested at the G₂/M phase. Although MGC-803 cells treated with low concentrations of PBA were also arrested at the G₀/G₁ phase, cells treated with high concentrations of PBA were arrested at the S phase.

CONCLUSION: The growth inhibitory effect of PBA on gastric cancer cells is associated with alteration of the cell cycle. For moderately-differentiated gastric cancer cells, the cell cycle was arrested at the G₀/G₁ and G₂/M phases. For lowly-differentiated gastric cancer cells, the cell cycle was arrested at the G₀/G₁ and S phases.

Detecting AFP mRNA in peripheral blood of the patients with hepatocellular carcinoma, liver cirrhosis and hepatitis

BACKGROUND

The low frequency of disseminated carcinoma cells in the blood now makes immunomagnetic bead sorting and reverse transcriptase-polymerase chain reaction (RT-PCR) technique more popular.

METHODS

Three milliliters of peripheral blood were collected from 91 patients and 18 normal donors. The circulating carcinoma cells were enriched with CD45 and Ber-EP4 immunomagnetic beads. The alpha-fetoprotein (AFP) mRNA was amplified with nested RT-PCR.

RESULTS

The total positive detection rate was 72.1%, 43.8%, 25.0%, 100%, and 66.7% in patients with hepatocellular carcinoma (HCC) untreated, liver cirrhosis (LC), hepatitis, metastasis liver cancer, and postsurgery of hepatocellular carcinoma, respectively. There was a significant difference among the patients with HCC, LC and hepatitis (HCC vs. LC, P<0.05; HCC vs. hepatitis, P<0.01) and between Class A and B of the HCC patients (P<0.05). Meanwhile, AFP mRNA was markedly expressed in HCC patients compared to the patients with no HCC (LC and hepatitis). The levels of aspartate transaminase (AST) and gamma-glutamyltranspeptidase (GGT) were significantly different in AFP mRNA-positive patients with autoimmune chronic active hepatitis B (CAHB) or LC in contrast to the corresponding negative patients.

CONCLUSION

Combining negative and positive immunomagnetic bead sorting and RT-PCR technique can effectively detect circulating tumor cells. AFP mRNA is a more reliable marker of metastasis compared to serum AFP.

Suppression of telomerase activity and arrest at G1 phase in human cervical cancer HeLa cells by all-trans retinoic acid

Of all neoplasms found in women, cervical cancer has the third highest incidence and causes the fourth most deaths. All-trans retinoic acid (ATRA) may be with chemopreventive potential on cervical cancer, but the mechanisms underlying is not clear. To investigate the mechanisms, human cervical cancer HeLa cells were treated with ATRA for 1, 2, 3, or 4 days in vitro. We found that ATRA inhibited the growth of HeLa cells in a dose-dependent manner at the concentrations from 0.3 to 9.6 mumol/L. Flow cytometric analysis showed that HeLa cells were arrested at G0/G1 phase by ATRA, and the aneuploidy was found when cells were treated for 4 days, which is the first report that ATRA causes aneuploid cycle in HeLa cells. The expression of human telomerase catalytic subunit messenger RNA was decreased remarkably by ATRA. These findings suggested that the inhibition of telomerase activity and arrest of cells at G0/G1 phase might be the key steps through which ATRA inhibits the proliferation of HeLa cells. Our results provide a possible mechanistic explanation for the growth inhibitory effect of ATRA on HeLa cells. Therefore, retinoids may have therapeutic potential to complement current treatments of cervical cancers.

The effects of all-trans-retinoic acid on cell cycle and alkaline phosphatase activity in pancreatic cancer cells

Pancreatic cancer is one of the tumors with the highest mortality, poorly responding to available chemotherapeutic agents. The objective of this study was to study the anticancer effects of all-trans retinoid acid, a functional form of vitamin A, on pancreatic cancer cells. Human pancreatic cancer MiaPaCa-2 cells were treated with 1, 5, 10, 20, 30, 40 and 50 microM ATRA for 1, 2, 3, 4, 5 or 6 d, respectively. Cell growth was determined by MTT viability assay. The cell cycle distribution and the alkaline phosphatase (ALP) activity were analyzed by flow cytometry and chemical analyzer, respectively. The results show that ATRA significantly inhibited the growth of MiaPaCa-2 cells at 40 and 50 microM. ATRA arrested pancreatic cancer cells at G0/G1 phase. The sub-G1 peak and DNA fragmentation were observed. There were time and dose dependent increases in alkaline phosphatase activity (ALP), an indicator of cell differentiation, upon treatment with ATRA when compared to controls. In conclusion, ATRA has an inhibitory effect on the cell growth of MiaPaCa-2, and its tumor suppressive effect is by means of cell cycle arrest and apoptosis induction.

Effects of survivin siRNA expression plasmid on proliferation of MGC-803 cells

AIM: To silence the expression of survivin gene in MGC-803 cells by the siRNA expression vector-based RNA interference (RNAi) technique, and to investigate its effects on the proliferation of MGC-803 cells.

METHODS: The survivin siRNA expression plasmid was transfected into MGC-803 cells by lipofectamine. Morphological changes of the cells were observed under invert microscope. The expression of survivin mRNA was determined by reverse transcription-polymerase chain reaction (RT-PCR). The changes of cell cycle and the cell proliferation were analyzed by flow cytometry and MTT assay, respectively.

RESULTS: Abnormal morphological changes of MGC-803 cells were observed in the group transfected with the survivin siRNA expression plasmid. The survivin siRNA expression plasmid significantly down-regulated the expression of survivin mRNA in MGC-803 cells with a percentage of 48.2% ( vs empty controls), and it arrested the cell cycle in G1 phase (77.4%). The cell proliferation was significantly inhibited, and the optical density in siRNA-transfected cells was markedly lower than that in the empty controls (24 h: 0.272 ± 0.048 vs 0.576 ± 0.018; 48 h: 0.270 ± 0.060 vs 0.809 ± 0.027; 72 h: 0.143 ± 0.046 vs 1.015 ± 0.075; all P < 0.01). The growth inhibitory rates of MGC-803 cells were 53.4%, 66.7%, and 86.3% after 24, 48, and 72 h of the transfection, respectively.

CONCLUSION: The expression of survivin in MGC-803 cells can be down-regulated by the plasmid-based RNAi technique, and the down-regulation can inhibit the cell proliferation in vitro.

[Gene studies and nobel prize]

Gene is a DNA sequence which can be expressed and produces gene products (protein or RNA). By 2003, there are 51 Nobel Prize owners related to gene studies. Among them, 44 persons are in physiology or medicine (account for 24.72% of total 178), 7 persons are in chemistry (account for 5.69% of total 123). The paper reviews them in following 6 aspects: Drosophlie melanogaster is a good material for gene study; the double helix model of DNA structure provides a hard foundation in gene study; the studies on gene regulation illuminate many functions of gene; genetic central dogma researches created 11 Noble Prize laureates; gene engineering technologies make possible to modify and use genes; and the thorough studies of gene characteristic made us easier to understand many life phenomena.

[The anti-proliferation and anti-migration dual effects of aloe-emodin on KB cells and its mechanism]

OBJECTIVE

To investigate the anti-proliferation and anti-migration dual effects of aloe-emodin on KB cells and its mechanisms.

METHODS

KB cells were treated with 2.5, 5, 10, 20 and 40 micromol/L aloe-emodin. Crystal violet assay was used to determine the long-term growth inhibition of aloe-emodin on human oral cancer KB cells. Scratch wound-healing motility assay was used to measure the antimigration effect The protein kinase C alpha and c-myc expression changes in protein levels were detected by Western blotting.

RESULTS

A durable cell growth inhibitory effect of aloe-emodin on KB cells was found. Treatment of aloe-emodin resulted in the inhibition of cell migration. The protein kinase C alpha and c-myc in protein levels were decreased upon treatment with aloe-emodin compared with controls.

CONCLUSIONS

The anti-proliferation and anti-migration effects of aloe-emodin on KB cells are associated with the suppression of protein kinase C pathway.

[Effect of microRNA on proliferation of human tongue carcinoma Tca8113 cells]

OBJECTIVE

To investigate the effects of microRNA (miRNA) on proliferation of cultured human squamous cell carcinoma of tongue Tca8113 cells.

METHODS

The mimics or inhibitors of miRNA-31 or miRNA-139 were transfected into Tca8113 cells using liposome. Tca8113 cell proliferation was detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay.

RESULTS

The absorbance (A) values of control group at 24 h, 48 h and 72 h were 0.125 +/- 0.002, 0.169 +/- 0.002 and 0.216 +/- 0.004, respectively. The mimics of miRNA-31 increased Tca8113 cell proliferation, with A values increasing to 0.136 +/- 0.001 (P < 0.001), 0.186 +/- 0.004 (P < 0.001) and 0.249 +/- 0.012 (P < 0.01), respectively. The inhibitors of miRNA-139 also increased A values to 0.148 +/- 0.002 (P < 0.001), 0.214 +/- 0.002 (P < 0.001) and 0.250 +/- 0.009 (P < 0.01), respectively. Contrast with these results, the inhibitors of miRNA-31 decreased Tca8113 cell proliferation, with A values decreasing to 0.145 +/- 0.001 and 0.155 +/- 0.011 (both of P < 0.001) at 48 h and 72 h, respectively. The mimics of miRNA-139 also decreased A to 0.135 +/- 0.001 and 0.170 +/- 0.009 (both of P < 0.001).

CONCLUSIONS

miRNA-31 and miRNA-139 play an important role in the carcinogenesis of human tongue carcinomas. It may become a new method for the treatment of tongue carcinomas by adjustment the activities of miRNA.