Interleukin-1 (IL-1) is a major “alarm” upstream pro-inflammatory cytokine that also affects immunity and hematopoiesis by inducing cytokine cascades. In the tumor arena, IL-1 is produced by malignant or microenvironmental cells. As a pleiotropic cytokine, IL-1 is involved in tumorigenesis and tumor invasiveness but also in the control of anti-tumor immunity. IL-1α and IL-1β are the major agonists of IL-1, while IL-1Ra is a physiological inhibitor of pre-formed IL-1. In their secreted form, IL-1α and IL-1β bind to the same receptors and induce the same biological functions, but IL-1α and IL-1β differ in their compartmentalization within the producing cell or the microenvironment. IL-1β is only active in its processed, secreted form, and mediates inflammation, which promotes carcinogenesis, tumor invasiveness, and immunosuppression, whereas IL-1α is mainly cell-associated and in the tumor context, when expressed on the cell membrane, it stimulates anti-tumor cell immunity manifested by tumor regression. In the tumor milieu, extracellular levels of IL-1α are usually low and do not stimulate broad inflammation that promotes progression. Immunosuppression induced by IL-1β in the tumor microenvironment, mainly through MDSC induction, usually inhibits or masks anti-tumor cell immunity induced by cell-associated IL-1α. However, in different tumor systems, redundant or unique patterns of IL-1α and IL-1β expression and function have been observed. Recent breakthroughs in inflammasome biology and IL-1β processing/secretion have spurred the development of novel anti-IL-1 agents, which are being used in clinical trials in patients with diverse inflammatory diseases. Better understanding of the integrative role of IL-1α and IL-1β in distinct malignancies will facilitate the application of novel IL-1 modulation approaches at the bedside, in cancer patients with minimal residual disease (MRD), as an adjunct to conventional approaches to reduce the tumor burden.

Oncogenic properties, along with the metabolic reprogramming necessary for tumour growth and motility, are acquired by cancer cells. Thus, tumour metabolism is becoming a target for cancer therapy. Here, cancer cell metabolism was tackled by silencing the expression of voltage-dependent anion channel 1 (VDAC1), a mitochondrial protein that controls cell energy, as well as metabolic and survival pathways and that is often over-expressed in many cancers. We demonstrated that silencing VDAC1 expression using human-specific siRNA (si-hVDAC1) inhibited cancer cell growth, both in vitro and in mouse xenograft models of human glioblastoma (U-87MG), lung cancer (A549), and triple negative breast cancer (MDA-MB-231). Importantly, treatment with si-hVDAC1 induced metabolic rewiring of the cancer cells, reversing their oncogenic properties and diverting them towards differentiated-like cells. The si-hVDAC1-treated residual “tumour” showed reprogrammed metabolism, decreased proliferation, inhibited stemness and altered expression of genes and proteins, leading to cell differentiation toward less malignant lineages. These VDAC1 depletion-mediated effects involved alterations in master transcription factors associated with cancer hallmarks, such as highly increased expression of p53 and decreased expression of HIF-1a and c-Myc that regulate signalling pathways (e.g., AMPK, mTOR). High expression of p53 and the pro-apoptotic proteins cytochrome c and caspases without induction of apoptosis points to functions for these proteins in promoting cell differentiation. These results clearly show that VDAC1 depletion similarly leads to a rewiring of cancer cell metabolism in breast and lung cancer and glioblastoma, regardless of origin or mutational status. This metabolic reprogramming results in cell growth arrest and inhibited tumour growth while encouraging cell differentiation, thus generating cells with decreased proliferation capacity. These results further suggest VDAC1 to be an innovative and markedly potent therapeutic target.

Mesenchymal stromal cells (MSCs) are multipotent and can be derived from different adult tissues including fat. Our repeated attempts to produce long-term proliferative cultures of rat abdominal adipose stem cells (aASCs) under normal oxygen concentration (21%) were unsuccessful. We set to examine the events controlling this cytostasis of aASCs and found that it resulted from overproduction of reactive oxygen species (ROS) that led to apoptosis. ROS overproduction in aASCs was accompanied by increased expression of NOX1 but not of NOX2 or NOX4. NOX family members are an important source of intracellular ROS pointing to NOX1 involvement in ROS accumulation. This was verified when aASCs that were grown under 3% oxygen conditions expanded long term, displaying reduced NOX1 expression and decreased ROS accumulation. NOX1 involvement in aASC cytostasis was reaffirmed when cells that were expanded under normoxic conditions in the presence of a specific NOX1 inhibitor, ML171, demonstrated reduced ROS accumulation, reduced apoptosis and long-term expansion. aASC expansion arrest was accompanied also by a weak fat differentiation and migratory potential, which was enhanced by NOX1 inhibition. This suggests an inhibitory role for NOX1-induced ROS overproduction on aASCs, their fat differentiation and migratory potential. In contrast to aASCs, similar cells produced from subcutaneous fat were easily expanded in normoxic cultures, exhibiting low ROS concentrations, a low number of apoptotic cells and improved fat differentiation and migration. Taken together, our results show, for the first time, that NOX1-induced ROS accumulation halts ASC expansion and reduces their differentiation and migratory potential under normoxic conditions. Importantly, this phenotype comprises a tissue-specific signature as it was evident in aASCs but not in subcutaneous ASCs. NOX-induced ROS accumulation and cytokine production by fat are part of the metabolic syndrome. The similarity of this phenomenon to aASC phenotype may indicate that they arise from similar molecular mechanisms.

The self-renewal potential of a cancer cell can be estimated by using particular assays, which include xenotransplantation in immunocompromised animals or culturing in non-adherent serum-free stem-cells media (SCM). However, whether cells with self-renewal potential actually contribute to disease is unknown. Here we investigated the tumorigenic potential and fate of cancer cells in an in-vivo melanoma model. We examined cell lines which were derived from the same parental line: a non-metastatic cell line (K1735/16), a metastatic cell line (K1735/M4) and a cell line which was selected in non-adherent conditions (K1735/16S). All cell lines exhibited similar proliferation kinetics when grown on culture plates. K1735/16 cells grown in soft agar or in suspension non-adherent conditions failed to form colonies or spheroids, whereas the other cell lines showed prominent colonogenicity and spheroid formation capacity. By using sphere limiting dilution analysis (SLDA) in serum-free media, K1735/16S and K1735/M4 cells grown in suspension were capable of forming spheroids even in low frequencies of concentrations, as opposed to K1735/16 cells. The tumorigenic potential of the cell lines was determined in SCID mice using intra footpad injections. Palpable tumors were evident in all mice. In agreement with the in-vitro studies, the K1735/M4 cell line exhibited the highest growth kinetics, followed by the K1735/16S cell line, whereas the K1735/16 cell line had the lowest tumor growth potential ( P <0.001). In contrast, when we repeated the experiments in syngeneic C3H/HeN mice, the K1735/16 cell line produced macroscopic tumors 30–100 days after injection, whereas K1735/M4 and K1735/16S derived tumors regressed spontaneously in 90–100% of mice. TUNEL analysis revealed significantly higher number of apoptotic cells in K1735/16S and K1735/M4 cell line-derived tumors compared to K1735/16 tumors (P<0.001). The models we have examined here raised the possibility, that cells with high-tumorigenic activity may be more immunogenic and hence are more susceptible to immune-regulation.