Mechanism of metformin enhancing the sensitivity of human pancreatic cancer cells to gem-citabine by regulating the PI3K/Akt/mTOR signaling pathway

OBJECTIVE

To investigate the effect of metformin (MET) on enhancing the sensitivity of human pancreatic cancer cells to gemcitabine (GEM) by regulating the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathway.

MATERIALS AND METHODS

The GEM-resistant human pancreatic cancer PANC-1/GEM cell line was established, and the proliferation ability of PANC-1 and PANC-1/GEM cell lines was detected using the Cell Counting Kit-8 (CCK-8), which was then detected by flow cytometry after they were labeled by Ki67. Quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR) and Western blotting were adopted to detect the difference in the mTOR expression between PANC-1 and PANC-1/GEM cell lines. The proliferation ability of PANC-1/GEM/MET and PANC-1/GEM cell lines was determined using CCK-8 after drug-resistant cell lines were treated with 20 mmol/L MET combined with 0.4 μmol/L GEM or 0.4 μmol/L GEM alone for 48 h. Colony formation assay was applied to detect the proliferation ability of cells. The difference in the expression of mTOR/PI3K/Akt between PANC-1/GEM/MET and PANC-1/GEM cell lines was tested via qRT-PCR and Western blotting, respectively.

RESULTS

Compared with PANC-1 cells, PANC-1/GEM cells had significantly enhanced proliferation ability (p<0.01). Flow cytometry results showed that the proliferation ability of PANC-1/GEM cells was notably enhanced (p<0.01). The expression level and phosphorylation level of mTOR in drug-resistant cell lines were increased (p<0.01). After the drug-resistant cell lines were treated with 20 mmol/L MET for 48 h, the proliferation ability of PANC-1/GEM/MET cells was evidently decreased compared with that of PANC-1/GEM cells (p<0.01). The messenger ribonucleic acid (mRNA) and protein expression levels of mTOR/PI3K/Akt were markedly down-regulated (p<0.01).

CONCLUSIONS

MET can regulate the PI3K/Akt/mTOR signaling pathway to enhance the sensitivity of human pancreatic cancer cells to GEM.

Expression and clinical significance of long-non-coding RNA GHET1 in pancreatic cancer

OBJECTIVE

To investigate the expression level and biological function of long non-coding RNA gastric carcinoma high expressed transcript 1 (lncRNA-GHET1) in pancreatic ductal adenocarcinoma (pancreatic cancer for short), to analyze the correlation between the expression of GHET1 and clinicopathological features and to explore the role and clinical significance of GHET1 in the development and progression of pancreatic cancer.

PATIENTS AND METHODS

The relative expression of GHET1 in 5 human pancreatic cancer cell lines was detected by quantitative Real-time polymerase chain reaction (qRT-PCR). The specific interference sequence of GHET1 was designed and transiently transfected into pancreatic cancer cells. qRT-PCR assay was used to detect the interference efficiency. Cell counting kit-8 (CCK-8) assay was used to detect the effect of the interference with GHET1 on the proliferation of pancreatic cancer cells. Flow cytometry was used to detect the effect of the interference with GHET1 on the cycle distribution and apoptosis. qRT-PCR was used to detect the relative expression of GHET1 in pancreatic cancer tissues compared with that in cancer-adjacent tissues. The correlation between the expression of GHET1 and the pathological features of pancreatic cancer patients was analyzed.

RESULTS

The expression of GHET1 in human pancreatic cancer cells was relatively high. The results of CCK-8 showed that the proliferation of tumor cells was inhibited after the interference with GHET1 expression. The results of flow cytometry showed that the expression of GHET1 was blocked at G1/G0 phase, and the apoptosis rate was increased. The results of qRT-PCR showed that the expression of GHET1 was upregulated in pancreatic cancer tissues of 49 out of 64 patients compared with that in cancer-adjacent tissues, and the highly expressed GHET1 was positively correlated with the tumor, node and metastasis (TNM) staging of pancreatic cancer.

CONCLUSIONS

Highly expressed GHET1 promotes the proliferation of pancreatic cancer, inhibits apoptosis and is related to TNM staging. The expression of GHET1 can be used as a potential molecular marker for the prognosis and therapeutic target of pancreatic cancer.

Characteristics of growth traits and their effects on body weight of G₁ individuals in the mud crab (Scylla paramamosain)

The mud crab (Scylla paramamosain) is considered a potentially important marine crab species for selective breeding. Here, we first examined sex ratio and differences in 16 growth traits between females and males in a G1 population of S. paramamosain, and we then analyzed the correlation between these growth traits and their effects on body weight (BW). Of these growth traits, nine were significantly different between sexes. In females, the correlation coefficients in all trait pairs ranged from 0.524 to 0.997. The traits carapace length (CL) and distance between lateral spine 2 (DLS2) significantly affected BW directly, with the path coefficients being 1.124 and -0.186, respectively. The determination coefficients of traits CL and DLS2 to BW were 1.263 and 0.035 with the total value being 0.951, indicating that the two traits were the key factors affecting BW. In males, the correlation coefficients in all trait pairs ranged from 0.881 to 0.999. The three traits body height (BH), fixed finger height of the claw (FFHC), and meropodite length of pereopod 2 (MLP2) significantly affected BW directly, with the path coefficients being 0.484, 0.300, and 0.225, respectively. The determination coefficients of traits BH, FFHC and MLP2 to BW were 0.234, 0.090 and 0.051, with the total value being 0.967, indicating that these three traits played a key role in affecting BW. Moreover, we constructed two best-fit linear regression equations, which were Y (BW) = 4.969 X1 (CL) - 0.758 X2 (DLS2) - 140.177 and Y (BW) = 3.806 X1 (BH) + 2.371 X2 (FFHC) + 1.725 X3 (MLP2) - 123.559 in females and males, respectively.

Relationships between parameters describing low-frequency electrical admittance locus plot of human palmar skin

Using a two-frequency three-electrode method, unipolar electrical admittance was measured in the palmar skin of 48 normal healthy humans. Characteristics of and relationships between the phase angle pi alpha/2, the conductance extrapolated at zero frequency G(O) and ion relaxation time tau obtained from the Cole-Cole equation were examined in a low-frequency region (up to 354 Hz). At base-line resting values, the three admittance parameters were interrelated according to the regression model; log tau i = A + B alpha i + D log G(O)i + epsilon i with R2 > or = 0.7434 (p < or = 0.0001), where A, B and D determined from regression analysis showed inter- and intra-individual variation. Multi-factor analyses of variance showed that alpha was greater in women than men (0.8025 versus 0.7545, p < 0.0023), and log G(O) decreased significantly with age (covariate coefficient = -0.0058 log microS cm-2 per year, p < 0.04). For evoked responses, alpha showed a very small change (maximum < 5%), tau decreased while G(O) increased. With increasing frequency, conductance responses increased in absolute amplitudes but decreased in relative changes (amplitude change divided by static level). Statistical analyses from clinical experimental materials (total 130 subjects) showed that the capacitive behaviour of admittance (due to alpha) presented significant variation between controls and patient groups. This may shed new light on the nature of the skin electrical admittance/impedance.

Characteristics of phase angle, extrapolated conductance and ion relaxation time in the low-frequency admittance locus plot of human palmar skin

The Cole-Cole equation can be used to model the electrical admittance of human skin. Using a previously published two-frequency (AC excitation) three-electrode method, the admittance locus plot (ALP) in the low-frequency region (< 1000 Hz) has been shown to be very well approximated by a straight line and can be described with frequency-independent parameters; phase angle alpha pi/2, conductance at extrapolated zero frequency G0 = 1/R0, and ion relaxation time tau. The aim of the paper is to study characteristics of alpha pi/2, G0 and tau in the low-frequency ALP of human palmar skin. The measured data are calculated off-line on a personal computer. Relative changes in alpha pi/2 are small (< 2%) even during a heavy physical-exercise period. G0 corresponds well with GDC obtained by the traditional DC method at excitations up to 200 mV (relative differences < or = 5% during baseline registration). Based on these findings, two comparatively simpler methods using only one lock-in amplifier are suggested: either measuring simultaneously with DC and at one frequency with AC excitation, or measuring at two different frequencies successively. The low-frequency part of the ALP can then be determined. G0, alpha and tau estimated by these simplified methods are in good agreement with the simultaneous two-frequency method and should therefore be suited for clinical applications.

Electrodermal and microcirculatory activity in patients with fibromyalgia during baseline, acoustic stimulation and cold pressor tests

The peripheral sympathetic activity was studied in 27 patients with fibromyalgia and 29 healthy controls through simultaneous measurements of electrodermal variables and blood flow at palmar skin sites during baseline, acoustic stimulation, and cold pressor tests. Compared to the controls, the patient group showed a significantly larger overall increase in the skin electrical conductance and less vasoconstriction during acoustic stimulation and cold pressor tests. These findings imply an increased activity of cholinergic and decreased activity of adrenergic components of the peripheral sympathetic nervous system in patients with fibromyalgia.