Objective To study the antitumor mechanisms of pirarubicin (THP) and its effect on preventing postoperative recurrence of superficial bladder cancer. Methods MTT assay, flow cytometry and transmission electron microscope were used to assess the effects of different concentration of THP on T24 cell line. THP 40 mg in 50 ml distil water was used intravesically in 60 patients with transitional cell carcinoma after TURBT to prevent tumor recurrence. Results T24 cells were suppressed significantly by THP in concentrations of 10 mg/L and 100 mg/L,the suppressive rates being 80% and 94% respectively. Apoptosis peak was evident before G1 phase. The characteristics of cell apoptosis, such as bubble formation in cytoplasm and condensed chromosome, were typically manifested. Cells became necrotic when the concentration of THP was 1 000 mg/L. One course of THP intravesical administration was completed in 58 cases. All patients were followed up for a mean of 18.8 months (range 6～24 months), and tumor recurred only in 5 cases (8.6%). Conclusions Suppression of tumor cell growth and inducing apoptosis, even necrosis, might be the main antitumor mechanisms of THP. Clinically, intravesical administration of THP after TURBT was effective and safe for preventing tumor recurrence.

Objective To prepare the standard molecular weight fragment mixtures. Methods Primers were designed to prepare clones which contained different sizes of standard molecular weight fragments. The template used for amplification of insert fragments was the pMD18-T vector. Bacteria culture and plasmid extraction were used to obtain abundant target fragment. Unlabeled DNA fragments were prepared by double digestion of the recombinant plasmids, and the fluorescent adaptor was prepared by annealing with two partial reverse complimentary DNA fragments. The unlabeled fragments and fluorescent adaptor were connected by DNA ligation reaction assisted with T4 DNA ligase. In this way, different sizes of standard molecular weight fragments were prepared. Standard molecular weight fragment mixture was finally prepared by mixing all the fragments together before purification. Results Ten standard molecular weight fragments of different sizes were prepared. The sizes of each fragment are 80bp, 124bp, 194bp, 224bp, 254bp, 304bp, 349bp, 399bp, 424bp and 454bp. The internal standard could accurately determine the size of PCR products amplified with the DNATyper15 kit. Conclusion Using this method, the standard molecular weight fragment mixture which meet the requirements of research and laboratory use was prepared, perfectly providing a new method for preparation of the DNA molecular weight standards. The peaks and the size of the prepared DNA internal lane standard are correct, which can be used to calculate the DNA fragments size in capillary electrophoresis.