Quiescence-like Metabolism to Push Cancer Out of the Race

LACTB, a Metabolic Therapeutic Target in Clinical Cancer Application

Serine beta-lactamase-like protein (LACTB) is the only mammalian mitochondrial homolog evolved from penicillin-binding proteins and β-lactamases (PBP-βLs) in bacteria. LACTB, an active-site serine protease, polymerizes into stable filaments, which are localized to the intermembrane space (IMS) of mitochondrion and involved in the submitochondrial organization, modulating mitochondrial lipid metabolism. Cancer pathogenesis and progression are relevant to the alterations in mitochondrial metabolism. Metabolic reprogramming contributes to cancer cell behavior. This article (1) evidences the clinical implications of LACTB on neoplastic cell proliferation and migration and tumor growth and metastasis as well as LACTB’s involvement in chemotherapeutic and immunotherapeutic responses; (2) sketches the structural basis for LACTB activity and function; and (3) highlights the relevant regulatory mechanisms to LACTB. The abnormal expression of LACTB has been associated with clinicopathological features of cancer tissues and outcomes of anticancer therapies. With the current pioneer researches on the tumor-suppressed function, structural basis, and regulatory mechanism of LACTB, the perspective hints at a great appeal of enzymic property, polymerization, mutation, and epigenetic and post-translational modifications in investigating LACTB’s role in cancer pathogenesis. This perspective provides novel insights for LACTB as a metabolic regulator with potential to develop targeted cancer therapies or neoadjuvant therapeutic interventions.

MicroRNA-1276 Promotes Colon Cancer Cell Proliferation by Negatively Regulating LACTB

Purpose

LACTB, regulated by a variety of microRNAs (miRNAs), is proven to be a tumor suppressor. However, there are few reports that LACTB in colon cancer cells is regulated by miRNA. Therefore, the aim of this study was to explore the miRNAs that regulate LACTB in colon cancer.

Patients and Methods

Data from TCGA were analyzed in starBase and GEPIA2, and Western blot and quantitative PCR (qPCR) were used to detect the expression of LACTB in colon cancer cell lines. MiRNAs targeting LACTB were predicted by MicroT-CDS, starBase, miRDB, mirDIP, and DIANA. The relationship between LACTB and miRNA was explored by dual-luciferase assay. MTT, propidium iodide (PI), Western blot, Annexin V-FITC/PI Kit, qPCR and transwell assay were used to detect the changes in cell proliferation, cell cycle, autophagy, apoptosis, epithelial-to-mesenchymal transition (EMT), cell migration, and invasiveness in colon cancer cells that overexpressed miR-1276 and/or LACTB.

Results

The results showed that the LACTB mRNA level was lower and the miR-1276 level was higher in colon cancer than in normal tissue. MiR-1276 inhibited the expression of LACTB. Furthermore, overexpression of miR-1276 in colon cancer cells increased proliferation, migration, invasiveness and EMT, and decreased autophagy and apoptosis. Supplementing LACTB suppressed these effects of miR-1276.

Conclusion

In conclusion, miR-1276, which may be a potential therapy for colon cancer, inhibits cell growth and promotes apoptosis by targeting LACTB in colon cancer cells.

LACTB Regulates PIK3R3 to Promote Autophagy and Inhibit EMT and Proliferation Through the PI3K/AKT/mTOR Signaling Pathway in Colorectal Cancer

Background

Colorectal cancer (CRC) is one of the most common aggressive malignancies. LACTB functions as a tumor suppressor, and previous findings have demonstrated that LACTB can inhibit epithelial-to-mesenchymal transition (EMT) and proliferation of breast cancer and CRC cells. However, few studies have investigated the roles of LACTB in autophagy and proliferation in CRC. The current study aimed to identify the roles of LACTB in EMT and proliferation associated with autophagy in CRC and to elucidate the probable molecular mechanisms through which LACTB are involved in these processes.

Materials and Methods

Transwell invasion, MTT, transmission electron microscopy, RNA-seq, immunoprecipitation, immunohistochemistry and Western blotting assays were performed to evaluate the migratory, invasive, proliferative and autophagic abilities of CRC cells, and the levels of active molecules involved in PI3K/AKT signaling were examined through Western blotting analysis. In addition, the in vivo function of LACTB was assessed using a tumor xenograft model.

Results

Weaker LACTB expression was found in CRC tissue samples than in nonmalignant tissue samples, and LACTB inhibited cell invasion, migration, and proliferation by promoting autophagy in vitro. Furthermore, the regulatory effects of LACTB on autophagy and EMT were partially attributed to the PI3K/AKT signaling pathway. The in vivo results also showed that LACTB modulated CRC tumorigenesis.

Conclusion

LACTB can regulate the activity of PIK3R3 to influence the level of PI3K, and it also promotes autophagy and inhibits EMT and proliferation in part through the PI3K/AKT/mTOR signaling pathway.

Tumor Cell Dormancy: Threat or Opportunity in the Fight against Cancer

Tumor dormancy, a clinically undetectable state of cancer, makes a major contribution to the development of multidrug resistance (MDR), minimum residual disease (MRD), tumor outgrowth, cancer relapse, and metastasis. Despite its high incidence, the whole picture of dormancy-regulated molecular programs is far from clear. That is, it is unknown when and which dormant cells will resume proliferation causing late relapse, and which will remain asymptomatic and harmless to their hosts. Thus, identification of dormancy-related culprits and understanding their roles can help predict cancer prognosis and may increase the probability of timely therapeutic intervention for the desired outcome. Here, we provide a comprehensive review of the dormancy-dictated molecular mechanisms, including angiogenic switch, immune escape, cancer stem cells, extracellular matrix (ECM) remodeling, metabolic reprogramming, miRNAs, epigenetic modifications, and stress-induced p38 signaling pathways. Further, we analyze the possibility of leveraging these dormancy-related molecular cues to outmaneuver cancer and discuss the implications of such approaches in cancer treatment.