Within the cell, several mechanisms exist to maintain homeostasis of the endoplasmic reticulum (ER). One of the primary mechanisms is the unfolded protein

A novel Pinellia ternata lectin was purified from the bulbs of a Chinese herb Pinellia ternata using a combination of hydrophobic chromatography and DEAE-ion exchange chromatography. The lectin was found to be a homodimer of 12093.3 Da subunits as determined by gel filtration and MS. Biochemical characterization of the lectin revealed the existence of a glycoprotein, which contains 3.22% neutral sugars. The N-terminal 10-amino acid sequence of the lectin, QGVNISGQVK, has not been reported for other lectins. The lectin had a special agglutinating activity with mouse erythrocytes at a minimum concentration of 8.0 ug/ml. The lectin was stable in the pH range of pH 5–12 and temperatures up to 80°C for 30 min. The results of MTT experiment showed that the lectin had significant effect towards tumor cells, the maximum inhibition of cell proliferation with Sarcoma 180, HeLa and K562 cell line were 85.2%, 74.6% and 59.4% respectively. Experimental therapy in vivo also showed that PTL apparently inhibited transplanted tumor in mice. Flow cytometric analysis demonstrated that PTL inhibited the proliferation of Sarcoma 180 in a time- and dose-dependent manner through inhibiting the transition of G₁/S and subsequently inducing G₀/G₁ cell cycle arrest. Thus, Pinellia ternata lectin displays a high potential for antitumor activity.

Previous studies revealed that PYROXD2 was more highly expressed in normal liver tissue and liver cell lines than in cancer tissue and cancer cell lines, which indicated that decreased PYROXD2 expression may be involved in hepatocarcinogenesis. To identify the mechanisms which regulate PYROXD2 gene transcription, we constructed a series of luciferase reporter plasmids and used them to perform luciferase‑based reporter assays with HepG2, Sk-hep1, L02 and 293T cells with the purpose of characterizing the PYROXD2 reporter region. Our results revealed that the transcription factor myeloid zinc finger 1 (MZF1) is necessary for PYROXD2 gene transcription and that it functions as a trans-activator. DNA binding assays revealed that the MZF1 protein binds to the cis-element TGGGGA located in the -320/-312 region of the PYROXD2 promoter. This promoter had a significantly enhanced activity when the MZF1 protein was overexpressed and a significantly decreased activity when the MZF1 protein expression was silenced. However, MZF1 gene expression was not significantly correlated with PYROXD2 protein expression in the samples of resected tumor tissues, which revealed that the PYROXD2 promoter transcription activity was determined by the aggregated effect of numerous transcription factors. This finding may be helpful in understanding the underlying mechanism which regulates the PYROXD2 expression.