Background information

Overall, it is estimated that there will be 20 million new cancer cases and 9.7 million cancer deaths globally in 2022. Among these, 49.2% of new cancer cases and 56.1% of cancer deaths occurred in Asia. Additionally, the cancer death burden in Africa and Asia was significantly higher than the corresponding incidence burden, a phenomenon that can be partly attributed to the fact that many newly diagnosed cancers are at advanced stages[1].


Figure 1 Global New Cancer Cases Chart1

It is worth noting that, unlike other countries or regions where the top five cancers account for no more than 51% of cancer-related deaths, in China, the top five cancers account for 67.5% of all cancer deaths[2].


Figure 2 The distribution of cases and deaths for the top 10 common cancers in 20221

In all, this study indicates that in 2022, there were approximately 20 million new cancer cases and nearly 10 million cancer deaths globally. By 2050, the number of new cancer cases per year is expected to reach 35 million1.

According to the World Health Organization, in 2022, cancer-related deaths accounted for about one-fifth of the total deaths[3]. With an estimated 20 million new cancer cases reported worldwide, cancer remains a major global issue. Its high incidence and mortality of cancer make its status as a leading cause of death worldwide. Cancer's influence extends beyond high mortality and incidence rates but also causes a significant economic burden. According to the International Agency for Research on Cancer (IARC), the annual costs associated with cancer treatment, productivity losses, and long-term care amount to trillions of dollars (IARC, 2023). In many low- and middle-income countries, limited resources hinder timely diagnosis and effective treatment, exacerbating the impact of cancer (WHO, 2023). Additionally, cancer intensifies health disparities, with specific populations experiencing higher incidence and mortality rates due to genetic factors, lifestyle, and environmental exposures (Global Cancer Statistics, 2023). While the economic and social impact of cancer underscores the urgent need for comprehensive strategies, advancements in treatment methods offer hope for improving patient outcomes and mitigating these challenges. Cancer treatment approaches have evolved significantly, encompassing a range of techniques tailored to the type and stage of the disease. These include surgery, radiation therapy, chemotherapy, targeted therapy, immunotherapy, cell therapy, and hormone therapy, each with its own set of indications and benefits. Surgery involves the physical removal of tumors and is often used when the cancer is localized. Radiation therapy uses high-energy radiation to target and destroy cancer cells, commonly used in combination with other treatments. Chemotherapy involves drugs that kill or inhibit the growth of cancer cells and can be used as a primary treatment or in conjunction with surgery or radiation. Targeted therapy focuses on specific molecular targets associated with cancer, aiming to minimize damage to normal cells. Immunotherapy leverages the body's immune system to recognize and destroy cancer cells more effectively. Cell therapy utilizes activated immune cells to eliminate tumor cells in the body. Lastly, hormone therapy is used for cancers that are hormone-sensitive, such as some types of breast and prostate cancers. These treatment options represent a broad arsenal in the fight against cancer, with ongoing research continuously enhancing their effectiveness and reducing side effects.

Probiotics and Promoters

Nowadays, although the improvement of cancer treatment methods has significantly increased the survival rates of cancer patients, most cancers still cannot be cured. The newly developed cancer treatment drugs, such as new chemotherapy drugs and immunotherapy, still have many shortcomings, such as poor targeting, the potential for drug resistance, and tumor recurrence. Therefore, genetically engineered bacteria are increasingly gaining attention as a novel disease diagnosis and treatment strategy. Engineered bacteria have been used to monitor liver metastasis, liver dysfunction, and gastrointestinal diseases, including inflammation, pathogen infections, and bleeding. Several bacteria, such as EcN (Nissle 1917, a probiotic), have been shown to selectively colonize tumors as they can infiltrate tumors, particularly in the hypoxic core of immunocompromised regions[4]. These findings underscore the importance of tailoring bacterial behavior to specific tumor environments. Previous research indicates that engineered bacteria can enhance their targeting in particular environments by coupling with genetic circuits that sense oxygen, pH, or lactate. These bacteria preferentially grow under acidic or hypoxic conditions and show increased tumor specificity in animal models with tumors[5],[6]. Consequently, these bacteria have been designed as tumor-specific drug delivery carriers to locally release drugs that inhibit tumor growth.

Our Design

Due to the poor targeting and significant side effects of traditional cancer drugs, they often harm normal cells. Immunomodulatory drugs also suffer from inaccurate targeting issues. So, we optimized probiotics to achieve higher precision and better therapeutic effects.


Figure 3 Drug Delivery Procedure

Our product development process is as follows: Firstly, we constructed a plasmid with a lactate-responsive promoter to control the expression of sfGFP (superfolder GFP). By detecting the expression of GFP, we qualitatively and quantitatively analyzed the activity of the lactate-responsive promoter at different lactate concentrations. Subsequently, the genes for either anti-PD-L1 antibody protein or azurin cytotoxic protein were incorporated into the lactate-responsive promoter vector to verify the expression of lactate-induced therapeutic proteins. Azurin is a protein from Pseudomonas aeruginosa, which can induce cancer cell apoptosis. The anti-PD-L1 antibody can block PD-L1 on tumor cells, thereby blocking its inhibition function on T cells7.

As probiotic injectable drugs, our products utilize the tumor-targeting ability of bacteria. After tracking the tumor and accumulating in the tumor area, the bacteria release the protein drugs. We can apply these plasmids to the probiotic bacterium Nissle 1917 and inject these probiotics into patients. Upon injection, these probiotics are delivered into the bloodstream and rapidly dispersed throughout the blood. As the blood circulates, the probiotics will traverse the arterial and capillary networks. They would be transported to various parts of the body, and utilizing their surface characteristics and biological markers, the probiotics can recognize the specific environment of tumors. The probiotics then migrate into the solid tumor through the capillary walls. Once the probiotics reach the tumor area, they would sense the elevated lactate concentration in the surrounding environment, thereby activating the promoter system within the probiotics. This promoter system has been meticulously designed to activate upon detecting lactate and induces the probiotics to produce and release the drugs. Activation of the promoter leads to the release of chemical and immune drugs into the tumor environment. These drugs then target the tumor cells for treatment. The chemical drugs will directly act on the tumor cells, while the immune drugs can activate the body's immune system to enhance its attack on the tumor[8],[9]. Because traditional chemical drugs cannot distinguish between tumor cells and normal cells, they attack both, and immune drugs lack accurate targeting. The advantage of our project lies in the use of a lactate promoter, which can effectively improve targeting precision and significantly reduce damage to normal cells. Additionally, due to the use of particular cancer treatment methods, our products will be economically affordable, making them accessible and usable for most families. Moreover, our drug has broad applicability and may effectively treat most types of tumors.

Goal

Previous studies have shown that probiotics use their inherent motility, chemotaxis, ability to induce inflammatory responses and evade immune systems to target and penetrate tumors uniquely6. Once colonised in tumors, probiotics expand within the immune-privileged tumor microenvironment (TME), enhancing immune surveillance and reducing immune suppression to induce anti-tumor immunity. However, probiotics alone cannot wholly eradicate tumors; thus, the prospect of bacteria carrying therapeutic payloads (drugs) holds great promise for cancer treatment. Based on synthetic biology, we have designed a precise probiotic therapy where probiotics, after colonizing the tumor, recognize the surrounding lactic acid environment[7]. A lactic acid-responsive promoter then initiates the expression of tumor drugs, allowing precise control of bacterial activity and drug expression and release within tumor tissues, thereby improving the safety and efficacy of probiotic-based cancer therapies.

References
      [1]Bray, F., et al. Global cancer statistics 2022: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA Cancer J Clin 74, 229-263 (2024).
      [2]Zheng, R.S., et al. [Cancer incidence and mortality in China, 2022]. Zhonghua Zhong Liu Za Zhi 46, 221-231 (2024).
      [3]https://www.who.int/news-room/fact-sheets/detail/cancer.
      [4]Gupta, K.H., Nowicki, C., Giurini, E.F., Marzo, A.L. & Zloza, A. Bacterial-Based Cancer Therapy (BBCT): Recent Advances, Current Challenges, and Future Prospects for Cancer Immunotherapy. Vaccines (Basel) 9(2021).
      [5]Chien, T., et al. Enhancing the tropism of bacteria via genetically programmed biosensors. Nat Biomed Eng 6, 94-104 (2022).
      [6]Gurbatri, C.R., Arpaia, N. & Danino, T. Engineering bacteria as interactive cancer therapies. Science 378, 858-864 (2022).
      [7]Nguyen, D.H., Chong, A., Hong, Y. & Min, J.J. Bioengineering of bacteria for cancer immunotherapy. Nat Commun 14, 3553 (2023).
      [8]Raman, V., et al. Intracellular delivery of protein drugs with an autonomously lysing bacterial system reduces tumor growth and metastases. Nat Commun 12, 6116 (2021).
      [9]Duong, M.T., Qin, Y., You, S.H. & Min, J.J. Bacteria-cancer interactions: bacteria-based cancer therapy. Exp Mol Med 51, 1-15 (2019).