The effect of targeted therapy on recruited cancer stem cells in a head and neck carcinoma model

pH-Triggered Transformable Peptide Nanocarriers Extend Drug Retention for Breast Cancer Combination Therapy

Increasing the penetration and accumulation of antitumor drugs at the tumor site are crucial in chemotherapy. Smaller drug-loaded nanoparticles (NPs) typically exhibit increased tumor penetration and more effective permeation through the nuclear membrane, whereas larger drug-loaded NPs show extended retention at the tumor site. In addition, cancer stem cells (CSCs) have unlimited proliferative potential and are crucial for the onset, progression, and metastasis of cancer. Therefore, a drug-loaded amphiphilic peptide, DDP- and ATRA-loaded Pep1 (DA/Pep1), is designed that self-assembles into spherical NPs upon the encapsulation of cis-diamminedichloroplatinum (DDP) and all-trans retinoic acid (ATRA). In an acidic environment, DA/Pep1 transforms into aggregates containing sheet-like structures, which significantly increases drug accumulation at the tumor site, thereby increasing antitumor effects and inhibiting metastasis. Moreover, although DDP treatment can increase the number of CSCs present, ATRA can induce the differentiation of CSCs in breast cancer to increase the therapeutic effect of DDP. In conclusion, this peptide nanodelivery system that transforms in response to the acidic tumor microenvironment is an extremely promising nanoplatform that suggests a new idea for the combined treatment of tumors.

Stochastic multicellular modeling of x-ray irradiation, DNA damage induction, DNA free-end misrejoining and cell death

The repair or misrepair of DNA double-strand breaks (DSBs) largely determines whether a cell will survive radiation insult or die. A new computational model of multicellular, track structure-based and pO₂-dependent radiation-induced cell death was developed and used to investigate the contribution to cell killing by the mechanism of DNA free-end misrejoining for low-LET radiation. A simulated tumor of 1224 squamous cells was irradiated with 6 MV x-rays using the Monte Carlo toolkit Geant4 with low-energy Geant4-DNA physics and chemistry modules up to a uniform dose of 1 Gy. DNA damage including DSBs were simulated from ionizations, excitations and hydroxyl radical interactions along track segments through cell nuclei, with a higher cellular pO₂ enhancing the conversion of DNA radicals to strand breaks. DNA free-ends produced by complex DSBs (cDSBs) were able to misrejoin and produce exchange-type chromosome aberrations, some of which were asymmetric and lethal. A sensitivity analysis was performed and conditions of full oxia and anoxia were simulated. The linear component of cell killing from misrejoining was consistently small compared to values in the literature for the linear component of cell killing for head and neck squamous cell carcinoma (HNSCC). This indicated that misrejoinings involving DSBs from the same x-ray (including all associated secondary electrons) were rare and that other mechanisms (e.g. unrejoined ends) may be important. Ignoring the contribution by the indirect effect toward DNA damage caused the DSB yield to drop to a third of its original value and the cDSB yield to drop to a tenth of its original value. Track structure-based cell killing was simulated in all 135306 viable cells of a 1 mm³ hypoxic HNSCC tumor for a uniform dose of 1 Gy.

Approaches to combat hypoxia in cancer therapy and the potential for in silico models in their evaluation

AIM

The negative impact of tumour hypoxia on cancer treatment outcome has been long-known, yet there has been little success combating it. This paper investigates the potential role of in silico modelling to help test emerging hypoxia-targeting treatments in cancer therapy.

METHODS

A Medline search was undertaken on the current landscape of in silico models that simulate cancer therapy and evaluate their ability to test hypoxia-targeting treatments. Techniques and treatments to combat tumour hypoxia and their current challenges are also presented.

RESULTS

Hypoxia-targeting treatments include tumour reoxygenation, hypoxic cell radiosensitization with nitroimidazoles, hypoxia-activated prodrugs and molecular targeting. Their main challenges are toxicity and not achieving adequate delivery to hypoxic regions of the tumour. There is promising research toward combining two or more of these techniques. Different types of in silico therapy models have been developed ranging from temporal to spatial and from stochastic to deterministic models. Numerous models have compared the effectiveness of different radiotherapy fractionation schedules for controlling hypoxic tumours. Similarly, models could help identify and optimize new treatments for overcoming hypoxia that utilize novel hypoxia-targeting technology.

CONCLUSION

Current therapy models should attempt to incorporate more sophisticated modelling of tumour angiogenesis/vasculature and vessel perfusion in order to become more useful for testing hypoxia-targeting treatments, which typically rely upon the tumour vasculature for delivery of additional oxygen, (pro)drugs and nanoparticles.

Shiga-like toxin I exerts specific and potent anti-tumour efficacy against gastric cancer cell proliferation when driven by tumour-preferential Frizzled-7 promoter

OBJECTIVES

Tumour-targeted gene therapy is a promising approach for effective control of gastric cancer cell proliferation. Our study aims to develop a cancer therapy which combines tumour-targeting promoters with cytotoxins.

METHODS

The expression of globotriaosylceramide (Gb3), which is a Shiga-like toxin I (Stx1) receptor, was verified in gastric cancer compared with normal stomach tissues as assessed by flow cytometry and immunohistochemical analysis. We therefore constructed the recombinant pFZD7-Stx1 plasmid vectors with tumour-preferential Frizzled-7 promoter and Stx1. pFZD7-Stx1 was used to treat gastric cancer in vitro and in vivo. The gastric cancer cell proliferation and tumour growth were identified after the transfection with the pFZD7-Stx1.

RESULTS

Globotriaosylceramide was obviously increased in gastric cancer compared with normal stomach. The gastric cancer cell proliferation and tumour growth decreased significantly after the transfection with the pFZD7-Stx1.

CONCLUSION

Frizzled-7 promoter is preferentially active, and Gb3 is abundant in gastric cancer cells. Frizzled-7 promoter and Stx1 may be used to determine a novel and relatively specific and potent gastric cancer therapeutic strategy.

The effect of targeted therapy on recruited cancer stem cells in a head and neck carcinoma model

OBJECTIVE

Head and neck cancers (HNC) are known for their repopulation ability driven by cancer stem cells (CSCs). While a small fraction of CSCs proliferates, there are quiescent CSCs that are long-lived and reside outside the cell cycle. Recruitment of quiescent CSCs into the cycle occurs as a response to cell loss and their proliferation may lead to treatment failure. Therefore, CSCs require a more targeted approach to be destroyed. An agent that sensitizes CSC response to treatment is all-trans-retinoic acid (ATRA). The aim of this work is to assess the impact of ATRA combined with radiotherapy on HNC and to analyse the interplay between these agents and cell recruitment.

METHODS

An in silico model is employed to grow a HNC consisting of all cancer cell lineages, with biologically valid kinetic and dynamic parameters. The fate of both cycling and quiescent cancer stem cells is assessed. The Linear Quadratic model is used to simulate radiotherapy, while cellular recruitment and the effects of ATRA on cancer stem cells are modelled based on literature data.

RESULTS

A Dose Enhancement Factor (DEF) was determined in order to undertake a quantitative assessment of the effect of ATRA on tumour control. Without recruitment, DEF for the tumour population is 1.06, indicating a slight radiosensitizing effect. Yet, when CSCs are being recruited, the dose enhancement factor is significantly greater (DEF = 1.89). Radiation-induced cell arrest and CSC sensitization by ATRA significantly decreases the dose required for CSC eradication in the cycling population. However, the tumour as a whole is not notably affected as the quiescent cells appear to dictate the shape of the survival curve.

CONCLUSIONS

The model shows that ATRA exhibits a powerful effect on CSCs when combined with radiotherapy. However, the more radioresistant quiescent cell population should not be ignored, as it can be a potential threat to treatment outcome when cells are recruited into the cell cycle.