Antitumor effect of para-toluenesulfonamide against lung cancer xenograft in a mouse model

Abstract

Background: Conventional chemotherapy and radiation therapy against non-small cell lung cancer (NSCLC) are relatively insensitive and unsatisfactory. Para-toluenesulfonamide (PTS), a unique antitumor drug for local intratumoral injection, shows an efficacy of severely suppressing solid tumor growth with mild side effects in clinical trials. The aim of this study was to investigate the effect of PTS on lung cancer H460 cells in vivo in nude mice and its underlying mechanisms in vitro.

Methods: A lung cancer model for in vivo experiment was established in BALB/c nude mice using H460 cells to examine the effect of local injection of PTS on tumor suppression. We also assessed the injury to the normal tissue by subcutaneous injection of PTS. In vitro, PTS was diluted into different doses for study on its antitumor mechanisms. We evaluated the necrotic effect of PTS on H460 cells by PI and Hoechst 33342 staining. Cell viability and membrane permeability were also determined by using CCK-8 and LDH assays respectively. All these tests were conducted in comparison with traditional local injection of anhydrous ethanol.

Results: PTS was shown to significantly inhibit the growth of H460 tumor xenografts in nude mice by inducing necrosis of the tumor histologically. Its effect on tumor growth was significantly stronger than that of anhydrous ethanol. By contrast, the injured normal tissue by PTS injection was less than that by ethanol. In vitro, PTS still demonstrated excellent necrotizing effect on H460 cells when diluted to a lower concentration. Detailed analysis of PTS on H460 cells indicated that PTS had a better effect on attenuating the cell viability and increasing the cell membrane permeability than ethanol at the same level.

Conclusions: PTS exhibits excellent inhibition effect on the growth of lung cancer by necrotizing tumor in vivo and in vitro, reducing tumor cell viability and augmenting the membrane permeability in vitro, with only mild injury to normal tissue. The antitumor effect of PTS on lung cancer in vivo and in vitro is stronger than that of ethanol.

Keywords: Para-toluenesulfonamide (PTS); antitumor agent; lung cancer; necrosis; therapy.

Figure 1

General condition of the mice at 24 h after first injection. A. PTS; B. Ethanol; C. 30% ethanol; D. Normal saline (NS).

Figure 2

The volume and weight of tumor xenografts. A. Growth curves of tumor xenografts in nude mice; B. Weights of extirpated tumor xenografts (#P<0.05 vs. Ethanol; *P<0.05 vs. 30% ethanol and NS).

Figure 3

Histopathological features of the tumors in nude mice (Magnification, ×100). A. PTS; B. Ethanol; C. 30% ethanol; D. NS.

Figure 4

Necrotic areas of the tumors from histopathological images (#P<0.05 vs. Ethanol; *P<0.05 vs. 30% ethanol and NS).

Figure 5

Necrotic effects of PTS and ethanol on H460 cells at the concentration of 1/100 under fluorescence microscopy (Magnification, ×200). A. PTS with Hoechst 33342 stained; B. PTS with PI stained in the same view; C. Hoechst 33342 stained; D. PI stained in the same view. Blue spots represented the cell nuclei stained by Hoechst 33342 and red spots were PI conjugates. Cells incubated with PTS were double stained, indicating necrosis.

Figure 6

Viability of H460 cells incubated with PTS and ethanol at different concentrations (1/200, 1/100, 1/50, 1/10) for 2 h (A), 6 h (B) and 24 h (C).

Figure 7

LDH release from H460 cells with continuous exposure to PTS and ethanol at different concentrations (1/1600, 1/800, 1/400, 1/200) for 2 h (A) and 6 h (B) (*P<0.05 PTS vs. ethanol).

Figure 8

Injury to normal tissue by PTS and ethanol. A, B, C. Morphological damage to normal tissue induced by PTS and ethanol (left side injected with ethanol and right side with PTS); D. Areas of damage to normal tissue (*P<0.05 vs. ethanol).

Figure 9

Histopathological features of the normal tissue incubated with PTS and ethanol in the nude mice. A, B and C were samples taken from the tissue damaged by PTS injection respectively at 0, 0.2 and 0.5 cm away from the injection spot. Accordingly, D, E and F were samples from the tissue damaged by ethanol injection respectively at 0, 0.2 and 0.5 cm away from the injection spot.