Fusobacterium nucleatum Promotes Chemoresistance to Colorectal Cancer by Modulating Autophagy
By Weiping Zou from China and the University of Michigan
Funding through China
1. What is the most important rule in chemistry?
1. Never lick the spoon.
Abstract: Gut microbiota are linked to chronic inflammation and carcinogenesis. Chemotherapy failure is the major cause of recurrence and poor prognosis in colorectal cancer patients. Here, we investigated the contribution of gut microbiota to chemoresistance in patients with colorectal cancer. We found that Fusobacterium(F.) nucleatum was abundant in colorectal cancer tissues in patients with recurrence post chemotherapy, and was associated with patient clinico-pathological characteristics. Furthermore, our bioinformatic and functional studies demonstrated that F. nucleatum promoted colorectal cancer resistance to chemotherapy. Mechanistically, F. nucleatum targeted TLR4 and MYD88 innate immune signaling and specific microRNAs to activate the autophagy pathway and alter colorectal cancer chemotherapeutic response. Thus, F. nucleatum orchestrates a molecular network of the Toll-like receptor, micro-RNAs, and autophagy to clinically, biologically, and mechanistically control colorectal cancer chemoresistance. Measuring and targeting F. nucleatum and its associated pathway will yield valuable insight into clinical management and may ameliorate colorectal cancer patient outcomes.
Notes:
* Colorectal cancer (CRC) is the third most common cancer and the second leading cause of cancer-related death worldwide. In advanced CRC patients, the purpose of chemotherapy is to shrink tumor size, reduce tumor growth, and inhibit tumor metastasis. In general, active cytotoxic drugs, including 5-fluorouracil (5-FU) and capecitabine, inhibit the enzyme activity of thymidylate synthase during DNA replication. Oxaliplatin, another chemotherapy drug, inhibits tumor cell growth and causes cell G2 phase arrest by covalently binding DNA and forming platinum-DNA adducts. The combination of these chemotherapeutic agents is widely used in the treatment of CRCs. The majority of patients with advanced CRC are initially responsive to the combined chemotherapy. However, the patients eventually experience tumor recurrence due to drug resistance, and the 5 year survival rate is lower than 10% in advanced CRC patients. Unfortunately, colon cancer patients are generally not responsive to novel immune checkpoint therapy. Thus, it is of paramount importance to elucidate the mechanism of chemotherapy resistance in CRC patients. Cancer chemoresistance results from a complex interplay between gene regulation and the environment
* Recent mouse studies have shown that the gut microbiota may modulate local immune responses and in turn affect chemotherapy and immunotherapy. Human gut microbiota are linked to inflammatory cytokine production
* A high amount of F. nucleatum was strongly associated with shorter recurrence free survival (RFS) (Figure 1D). The five-year recurrence survival was substantially shorter in the F. nucleatum-high group than the F. nucleatumlow group. Receiver operating characteristic (ROC) curve analysis was conducted to predict the potential CRC recurrence using either AJCC stage or the amount of F. nucleatum
* Given the role of the autophagy pathway in cellular survival, our data suggest that F. nucleatum may cause autophagy pathway activation and potentially support cancer chemoresistance
* Moreover, F. nucleatum had no protective effect on HCT116 cells and HT29 cells treated with Doxorubicin
* We found that the F. nucleatum-induced chemoresistant effect was abolished by CQ treatment in HCT116 cells (Figures 3A and 3B) and HT29 cells
* The data indicate that F. nucleatum may induce autophagy activation via increasing ULK1 and ATG7 expression
* To explore the mechanism by which F. nucleatum induced upregulation of pULK1, ULK1, and ATG7 at both the mRNA and protein level
* Capecitabine (and 5-FU) in combination with platinum-based chemotherapy has been widely used to treat different types of cancer including CRC. Although CRC patients’ initial responses to surgical debulking and chemotherapy is often effective, relapse with drug-resistant cancer usually occurs and patients succumb to disease. Unfortunately, CRC patients are generally not responsive to novel immune checkpoint therapy. Conventional chemotherapy remains the first line therapy for patients with CRC. Thus, understanding the mechanisms of chemoresistance in CRC is essential to optimizing current therapeutic strategies.
* Recent mouse studies have shown that the gut microbiota may modulate local immune responses and in turn affect chemotherapy and immunotherapy
* Furthermore, our data raise an important clinical question: are conventional chemotherapeutic regimens including Capecitabine plus Oxaliplatin suitable for CRC patients with a high amount of F. nucleatum? Alternatively, we suggest that CRC patients with a high amount of F. nucleatum may be treated with conventional chemotherapy in combination with anti-F. nucleatum treatment and/or an autophagy inhibitor. Thus, it is important to detect F. nucleatum and its associated pathway and differentially manage patients with different levels of F. nucleatum.
Dinner Party Tag Line: Researchers from China figured out that one of the reasons colorectal cancer recurrence is so high is because of an imbalance in patients gut microbiota. Basically, one bacteria species in your gut is protecting colorectal cancer from common chemotherapeutics.