Intracellular signaling modules linking DNA damage to secretome changes in senescent melanoma cells

Mitofusin 1 silencing decreases the senescent associated secretory phenotype, promotes immune cell recruitment and delays melanoma tumor growth after chemotherapy

Cellular senescence is a therapy endpoint in melanoma, and the senescence-associated secretory phenotype (SASP) can affect tumor growth and microenvironment, influencing treatment outcomes. Metabolic interventions can modulate the SASP, and mitochondrial energy metabolism supports resistance to therapy in melanoma. In a previous report we showed that senescence, induced by the DNA methylating agent temozolomide, increased the level of fusion proteins mitofusin 1 and 2 in melanoma, and silencing Mfn1 or Mfn2 expression reduced interleukin-6 secretion by senescent cells. Here we expanded these observations evaluating the secretome of senescent melanoma cells using shotgun proteomics, and explored the impact of silencing Mfn1 on the SASP. A significant increase in proteins reported to reduce the immune response towards the tumor was found in the media of senescent cells. The secretion of several of these immunomodulatory proteins was affected by Mfn1 silencing, among them was galectin-9. In agreement, tumors lacking mitofusin 1 responded better to treatment with the methylating agent dacarbazine, tumor size was reduced and a higher immune cell infiltration was detected in the tumor. Our results highlight mitochondrial dynamic proteins as potential pharmacological targets to modulate the SASP in the context of melanoma treatment.

Protective effects of palbociclib on colitis-associated colorectal cancer

Background

Chronic or recurrent inflammatory injury to the intestinal mucosa is closely related to inflammation-related colorectal cancer (CRC). This study aimed to examine the protective effects of palbociclib, a stimulator of interferon genes (STING) antagonist, on colitis-related colorectal carcinogenesis.

Methods

Bioinformatic analyses, including Gene Ontology (GO) enrichment, gene set enrichment analysis (GSEA), and network analysis, were conducted. Male C57BL/6 mice were administered azoxymethane (AOM) and dextran sulfate sodium (DSS), followed by treatment with palbociclib for 6 weeks. The general conditions of mice were observed and recorded. The colon histopathology was assessed based on hematoxylin and eosin (H&E) staining results. Relative messenger RNA (mRNA) expression levels of interferon b1 (Ifnb1), interleukin 6 (Il6), and interleukin 1b (Il1b) in colon were estimated based on quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) analysis.

Results

The STING signaling pathway was significantly upregulated in stages III and IV of CRC in The Cancer Genome Atlas (TCGA)-CRC cohort. After treatment with AOM/DSS, the weight of mice decreased significantly, whereas administration of palbociclib partially reversed this trend. The mouse colon treated with AOM/DSS showed significant pathological damages, disorderly epithelial cell structure, atypical hyperplasia, and infiltration of several inflammatory cell types; however, the colon damage was remarkably reduced upon treatment with palbociclib. It was also found that palbociclib almost abolished the increase in the downstream effectors of STING-mediated transcription in the colon tissue treated with AOM/DSS, as evidenced by the transcription levels of Ifnb1, Il6, and Il1b.

Conclusions

These findings indicate that the STING pathway is closely associated with CRC. Palbociclib significantly alleviates tumor development in AOM/DSS-induced colitis-associated CRC.

Biomarkers found in the tumor interstitial fluid may help explain the differential behavior among keratinocyte carcinomas

Basal Cell Carcinomas (BCC) and cutaneous Squamous Cell Carcinomas (SCC) are the most frequent types of cancer, and both originate from the keratinocyte transformation, giving rise to the group of tumors called keratinocyte carcinomas (KC). The invasive behavior is different in each group of KC and may be influenced by their tumor microenvironment. The principal aim of the study is to characterize the protein profile of the Tumor Interstitial Fluid (TIF) of KC to evaluate changes in the microenvironment that could be associated with their different invasive and metastatic capabilities. We obtained TIF from 27 skin biopsies and conducted a label-free quantitative proteomic analysis comparing 7 BCCs, 16 SCCs, and 4 Normal Skins. A total of 2945 proteins were identified, 511 of them quantified in more than half of the samples of each tumoral type. The proteomic analysis revealed differentially expressed TIF-proteins that could explain the different metastatic behavior in both KC. In detail, the SCC samples disclosed an enrichment of proteins related to cytoskeleton, such as Stratafin and Ladinin1. Previous studies found their up-regulation positively correlated with tumor progression. Furthermore, the TIF of SCC samples was enriched with the cytokines S100A8/S100A9. These cytokines influence the metastatic output in other tumors through the activation of NF-kB signaling. According to this, we observed a significant increase in nuclear NF-kB subunit p65 in SCCs but not in BCCs. In addition, the TIF of both tumors was enriched with proteins involved in the immune response, highlighting the relevance of this process in the composition of the tumor environment. Thus, the comparison of the TIF composition of both KC provides the discovery of a new set of differential biomarkers. Among them, secreted cytokines such as S100A9 may help explain the higher aggressiveness of SCCs, while Cornulin is a specific biomarker for BCCs. Finally, the proteomic landscape of TIF provides key information on tumor growth and metastasis, which can contribute to the identification of clinically applicable biomarkers that may be used in the diagnosis of KC, as well as therapeutic targets.

Early contribution of germline and nevi genetic alterations to a rapidly-progressing cutaneous melanoma patient: a case report

BACKGROUND

Cutaneous melanoma is the skin cancer with the highest mutational burden and metastatic rate. Early genetic alterations and biomarkers of distant progression are a point of interest. In addition to germline-susceptibility loci, almost 30% of melanomas arise from precursor benign nevi lesions, providing a source for malignant transformation.

CASE PRESENTATION

Patient#009 developed a cutaneous melanoma over a nevus, followed by progression to regional and distant metastases in months, unresponsive to targeted therapy. To search for the genetic contribution to this rapid progression, a longitudinal analysis was performed through WES of germline, nevi, primary tumor, and a metastatic lymph node. Differential SNP/INDEL and CNV gene alterations, with functional impact on key pathways and cancer hallmarks in each step of evolution, were discerned. Tumor-associated nevus was, for the first time, split into two sections, distant and adjacent to the primary tumor, to study its heterogeneity. Shared SNP alterations, with stable allele fraction from germline to metastasis were detected, mainly affecting DNA repair genes and promoting genome instability. Early somatic alterations, shared by nevi and primary and metastatic tumors, included BRAF^V600E and focal copy-loss of several genes, acquiring additional cancer hallmarks. Phylogenetic analyses revealed that these common somatic alterations would provide a "bridge", allowing progression from a benign to a malignant state. Distant and adjacent nevi were rich in alterations, presenting differential SNP and CNV alterations. Upon tumor transformation, a marked increase in CNV over SNP alterations was determined. Both the number of SNP and CNV-affected genes, including known driver genes, increased throughout progression, although TMB levels remained lower than expected for melanoma. Typical alterations in BRAF^V600E tumors related to intrinsic resistance to targeted therapy were found, including BRAF amplification and loss of PTEN, CDKN2A/B, and TP53 surveillance genes. Finally, numerous metastatic alterations were detected, further promoting tumor progression.

CONCLUSIONS

In this patient, longitudinal WES analysis revealed a sequential and cumulative pattern of genetic alterations, where germline and nevi somatic events contributed early to its rapid clinical progression. In this case report, we found tumor-associated nevi as genetically heterogeneous precursor entities, in which potential prognostic biomarkers should be studied prospectively.

STING promotes proliferation and induces drug resistance in colorectal cancer by regulating the AMPK-mTOR pathway

BACKGROUND

In recent years, reports regarding stimulator of interferon genes (STING) and the progression of colorectal cancer (CRC) have emerged rapidly, yet their association remains controversial. This research was aimed to provide an insight into the prognostic biomarker and therapeutic target significance of STING in CRC.

METHODS

CRC Cell lines of HCT116 and SW480, as well as 32 paired CRC specimens were chosen for this study. STING expressions were examined by immunohistochemistry to evaluate the correlation with clinicopathological factors. Data analysis of STING expressions in colon cancer and rectal cancer were performed using The Cancer Genome Atlas (TCGA) database. siRNA was transfected into cell lines for knocking down the expression of STING. Transwell assay was employed to evaluate cell migration and invasiveness. CCK-8 assay was used for assessing the change of cell proliferation. Drug sensitive test was involved to evaluate drug resistance of cell lines. Gene Set Enrichment Analysis (GSEA) was applied for exploring potential downstream mechanism of STING in CRC progression and Western blotting is used for mechanism validation.

RESULTS

In the thirty-two paired CRC and adjacent normal tissues, we found a significant up-regulated in STING expression with immunohistochemical staining in cancer tissues compared with adjacent normal tissues (P<0.01), which was correlated with the tumor-node-metastasis (TNM) stage of patients (P=0.028). Meanwhile, GESA enrichment analysis indicated a remarkable change in mTOR signaling following STING regulation. In HCT116 and SW480 cell lines of CRC, When STING was down-regulated, its biological behavior of cell viability, cell invasion and drug sensitivity to 5-fluorouracil were significantly reduced (P<0.05), we also observed the up-regulation of P-AMPK (P<0.05) and down-regulation of p-mTOR (P<0.05).

CONCLUSIONS

STING expressions was significantly up-regulated in CRC tissues. Expression of STING was correlated with the TNM stage of patients. STING is found to promote cell proliferation, invasion ability and drug resistance mediating AMPK-mTOR signaling in CRC. STING could be a promising target for the sensitization of chemotherapy and inhibits CRC progression.

STING Signaling and Skin Cancers

Recent developments in immunotherapy against malignancies overcome the disadvantages of traditional systemic treatments; however, this immune checkpoint treatment is not perfect and cannot obtain a satisfactory clinical outcome in all cases. Therefore, an additional therapeutic option for malignancy is needed in oncology. Stimulator of interferon genes (STING) has recently been highlighted as a strong type I interferon driver and shows anti-tumor immunity against various malignancies. STING-targeted anti-tumor immunotherapy is expected to enhance the anti-tumor effects and clinical outcomes of immunotherapy against malignancies. In this review, we focus on recent advancements in the knowledge gained from research on STING signaling in skin cancers. In addition to the limitations of STING-targeted immunotherapy, we also discuss the clinical application of STING agonists in the treatment of skin cancer.

The Dynamic Process and Its Dual Effects on Tumors of Therapy-Induced Senescence

Cellular senescence is traditionally considered as stable cell cycle arrest state with other phenotypic alterations including the production of an array of cytokines and growth factors. Cancer cells undergo senescence in response to chemotherapeutic agents, radiotherapy and molecular targeted therapy. This form of senescence is termed therapy-induced senescence (TIS) and represents a desirable target in cancer therapy. Recent studies have shown that cellular senescence is a highly heterogeneous and dynamic process. Apart from being cleared by the immune system, the senescent cancer cells may survive for a long time and escape from senescence state. Notably, these cells even have the potential to regain stem-like state with high aggressiveness that eventually facilitates cancer recurrence. Furthermore, the senescence-associated secretory phenotype (SASP) of senescent cells is not always the same, and could establish immunosuppression and a protumor microenvironment. Given these detrimental effects, senescence-inducing chemotherapy followed by senotherapy (the “one–two punch” approach), has emerged. This combined therapy could mitigate unnecessary side effects of the persistent senescent cells, reduce the toxicity of pro-senescence therapy and prolong the survival of cancer patients, and it has a potential future in the precise treatment of cancer. Herein, we review the complex effects of therapy-induced senescence in cancer and highlight the great promise of two-step strategies in anticancer therapies.