Empowering the Potential of CAR-T Cell Immunotherapies by Epigenetic Reprogramming

The Tumor Stroma of Squamous Cell Carcinoma: A Complex Environment That Fuels Cancer Progression

The tumor microenvironment (TME), a complex assembly of cellular and extracellular matrix (ECM) components, plays a crucial role in driving tumor progression, shaping treatment responses, and influencing metastasis. This narrative review focuses on the cutaneous squamous cell carcinoma (cSCC) tumor stroma, highlighting its key constituents and their dynamic contributions. We examine how significant changes within the cSCC ECM-specifically, alterations in fibronectin, hyaluronic acid, laminins, proteoglycans, and collagens-promote cancer progression, metastasis, and drug resistance. The cellular composition of the cSCC TME is also explored, detailing the intricate interplay of cancer-associated fibroblasts (CAFs), mesenchymal stem cells (MSCs), endothelial cells, pericytes, adipocytes, and various immune cell populations. These diverse players modulate tumor development, angiogenesis, and immune responses. Finally, we emphasize the TME's potential as a therapeutic target. Emerging strategies discussed in this review include harnessing the immune system (adoptive cell transfer, checkpoint blockade), hindering tumor angiogenesis, disrupting CAF activity, and manipulating ECM components. These approaches underscore the vital role that deciphering TME interactions plays in advancing cSCC therapy. Further research illuminating these complex relationships will uncover new avenues for developing more effective treatments for cSCC.

Plasticity and resistance of cancer stem cells as a challenge for innovative anticancer therapies - do we know enough to overcome this?

According to the CSC hypothesis, cancer stem cells are pivotal in initiating, developing, and causing cancer recurrence. Since the identification of CSCs in leukemia, breast cancer, glioblastoma, and colorectal cancer in the 1990s, researchers have actively investigated the origin and biology of CSCs. However, the CSC hypothesis and the role of these cells in tumor development model is still in debate. These cells exhibit distinct surface markers, are capable of self-renewal, demonstrate unrestricted proliferation, and display metabolic adaptation. CSC phenotypic plasticity and the capacity to EMT is strictly connected to the stemness state. CSCs show high resistance to chemotherapy, radiotherapy, and immunotherapy. The plasticity of CSCs is significantly influenced by tumor microenvironment factors, such as hypoxia. Targeting the genetic and epigenetic changes of cancer cells, together with interactions with the tumor microenvironment, presents promising avenues for therapeutic strategies. See also the Graphical abstract(Fig. 1).

Antigen experience history directs distinct functional states of CD8+ CAR T cells during the anti-leukemia response

Chimeric antigen receptor T cells are an effective therapy for B-lineage malignancies. However, many patients relapse and this therapeutic has yet to show strong efficacy in other hematologic or solid tumors. One opportunity for improvement lies in the ability to generate T cells with desirable functional characteristics. Here, we dissect the biology of CD8+ CAR T cells (CAR8) by controlling whether the T cell has encountered cognate TCR antigen prior to CAR generation. We find that prior antigen experience influences multiple aspects of in vitro and in vivo CAR8 functionality, resulting in superior effector function and leukemia clearance in the setting of limiting target antigen density compared to antigen-inexperienced T cells. However, this comes at the expense of inferior proliferative capacity, susceptibility to phenotypic exhaustion and dysfunction, and inability to clear wildtype leukemia in the setting of limiting CAR+ cell dose. Epigenomic and transcriptomic comparisons of these cell populations identified overexpression of the Runx2 transcription factor as a novel strategy to enhance CAR8 function, with a differential impact depending on prior cell state. Collectively, our data demonstrate that prior antigen experience determines functional attributes of a CAR T cell, as well as amenability to functional enhancement by transcription factor modulation.