Tumor-associated myeloid-derived cells (MDCs) significantly impact cancer prognosis and treatment responses due to their remarkable plasticity and tumorigenic behaviors. Here, we integrate single-cell RNA-sequencing data from different cancer types, identifying 29 MDC subpopulations within the tumor microenvironment. Our analysis reveals abnormally expanded MDC subpopulations across various tumors and distinguishes cell states that have often been grouped together, such as TREM2+ and FOLR2+ subpopulations. Using deconvolution approaches, we identify five subpopulations as independent prognostic markers, including states co-expressing TREM2 and PD-1, and FOLR2 and PDL-2. Additionally, TREM2 alone does not reliably predict cancer prognosis, as other TREM2+ macrophages show varied associations with prognosis depending on local cues. Validation in independent cohorts confirms that FOLR2-expressing macrophages correlate with poor clinical outcomes in ovarian and triple-negative breast cancers. This comprehensive MDC atlas offers valuable insights and a foundation for futher analyses, advancing strategies for treating solid cancers.

Reversible electropermeabilization (RE) is an ultrastructural phenomenon that transiently increases the permeability of the cell membrane upon application of electrical pulses. The technique was described in 1972 by Neumann and Rosenheck and is currently used in a variety of applications, from medicine to food processing. In oncology, RE is applied for the intracellular transport of chemotherapeutic drugs as well as the delivery of genetic material in gene therapies and vaccinations. This review summarizes the physical changes of the membrane, the particularities of bleomycin, and the immunological aspects involved in electrochemotherapy and gene electrotransfer, two important EP-based cancer therapies in human and veterinary oncology.

Recent preclinical and clinical studies have used viral vectors in gene therapy research, especially nonreplicating adenovirus encoding strategic therapeutic genes for cancer treatment. Adenoviruses were the first DNA viruses to go into therapeutic development, mainly due to well-known biological features: stability in vivo, ease of manufacture, and efficient gene delivery to dividing and nondividing cells. However, there are some limitations for gene therapy using adenoviral vectors, such as nonspecific transduction of normal cells and liver sequestration and neutralization by antibodies, especially when administered systemically. On the other hand, adenoviral vectors are amenable to strategies for the modification of their biological structures, including genetic manipulation of viral proteins, pseudotyping, and conjugation with polymers or biological membranes. Such modifications provide greater specificity to the target cell and better safety in systemic administration; thus, a reduction of antiviral host responses would favor the use of adenoviral vectors in cancer immunotherapy. In this review, we describe the structural and molecular features of nonreplicating adenoviral vectors, the current limitations to their use, and strategies to modify adenoviral tropism, highlighting the approaches that may allow for the systemic administration of gene therapy.

Preventing the replication of adenovirus could have practical uses, such as controlling infection with wild-type virus or in applications involving recombinant vectors. Mainly transient methods have been used to inhibit adenovirus replication, including siRNA or drugs. Here, we tested whether stable expression of shRNA designed to target hexon, Iva2, or pol can inhibit the replication of a recombinant adenoviral vector, Ad-LacZ (serotype 5, E1/E3 deleted), in 293T cells. Significant knockdown correlating with reduced Ad-LacZ replication was achieved only when hexon was targeted. Cell sorting and isolation of cellular clones further accentuated knockdown of the hexon transcript, reduced protein levels by more than 90%, and diminished adenovirus production. As visualized by transmission electron microscopy, the cellular clone expressing the hexon-specific shRNA yielded 89.2% fewer particles compared to the parental 293T cells. Full scale production followed by purification revealed a 90.2% reduction in Ad-LacZ biological titer. These results support the notion that stable expression of shRNA can be used as a means to control adenovirus replication.