Background: Recent studies have shown that adipose tissue is an endocrine organ that releases various cytokines. Objective: To investigate the production of growth factors and proinflammatory cytokines in infrapatellar fat pad specimens. Methods: Infrapatellar fat pad tissues were obtained from patients during knee surgery. Protein levels of basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), tumour necrosis factor (TNF)α, and interleukin (IL)6 in homogenised tissues were measured by an enzyme immunoassay. Gene expressions for those cytokines were examined by reverse transcription-polymerase chain reaction (RT-PCR). Localisation of bFGF and VEGF was evaluated by immunohistochemistry and in situ hybridisation. Results: Infrapatellar fat pads were found to contain various protein levels of bFGF, VEGF, TNFα, and IL6. Further, gene expressions for these cytokines were detected by RT-PCR. Immunohistochemistry and in situ hybridisation showed that the expressions of both bFGF and VEGF were localised in immature adipocytes, interstitial undifferentiated mesenchymal cells, and vascular endothelial cells. Conclusion: The production of bFGF, VEGF, TNFα, and IL6 in the infrapatellar fat pad was demonstrated. Although synovial cells and articular chondrocytes are thought to be primary sources of cytokines found in knee synovial fluids, the results suggest that they may also originate from this fat pad.

The tumor suppressor protein p53 tonically suppresses autophagy when it is present in the cytoplasm. This effect is phylogenetically conserved from mammals to nematodes, and human p53 can inhibit autophagy in yeast, as we show here. Bioinformatic investigations of the p53 interactome in relationship to the autophagy-relevant protein network underscored the possible relevance of a direct molecular interaction between p53 and the mammalian ortholog of the essential yeast autophagy protein Atg17, namely RB1-inducible coiled-coil protein 1 (RB1CC1), also called FAK family kinase-interacting protein of 200 KDa (FIP200). Mutational analyses revealed that a single point mutation in p53 (K382R) abolished its capacity to inhibit autophagy upon transfection into p53-deficient human colon cancer or yeast cells. In conditions in which wild-type p53 co-immunoprecipitated with RB1CC1/FIP200, p53 (K382R) failed to do so, underscoring the importance of the physical interaction between these proteins for the control of autophagy. In conclusion, p53 regulates autophagy through a direct molecular interaction with RB1CC1/FIP200, a protein that is essential for the very apical step of autophagy initiation.

The role of mesenchymal stem cells (MSC) in osteosarcoma (OS), the most common primary tumor of bone, has not been extensively elucidated. We have recently shown that OS is characterized by interstitial acidosis, a microenvironmental condition that is similar to a wound setting, in which mesenchymal reactive cells are activated to release mitogenic and chemotactic factors. We therefore intended to test the hypothesis that, in OS, acid‐activated MSC influence tumor cell behavior. Conditioned media or co‐culture with normal MSC previously incubated with short‐term acidosis (pH 6.8 for 10 hr, H⁺‐MSC) enhanced OS clonogenicity and invasion. This effect was mediated by NF‐κB pathway activation. In fact, deep‐sequencing analysis, confirmed by Real‐Time PCR and ELISA, demonstrated that H⁺‐MSC differentially induced a tissue remodeling phenotype with increased expression of RelA, RelB and NF‐κB1, and downstream, of CSF2/GM‐CSF, CSF3/G‐CSF and BMP2 colony‐promoting factors, and of chemokines (CCL5, CXCL5 and CXCL1), and cytokines (IL6 and IL8), with an increased expression of CXCR4. An increased expression of IL6 and IL8 were found only in normal stromal cells, but not in OS cells, and this was confirmed in tumor‐associated stromal cells isolated from OS tissue. Finally, H⁺‐MSC conditioned medium differentially promoted OS stemness (sarcosphere number, stem‐associated gene expression), and chemoresistance also via IL6 secretion. Our data support the hypothesis that the acidic OS microenvironment is a key factor for MSC activation, in turn promoting the secretion of paracrine factors that influence tumor behavior, a mechanism that holds the potential for future therapeutic interventions aimed to target OS.

Altered pH gradient at the plasma membrane of osteosarcoma cells is a key mechanism of drug resistance