Distinct senescence mechanisms restrain progression of dysplastic nevi.

Telomerase reverse transcriptase (TERT) promoter mutations (TPMs) are frequently found in different cancer types, including ∼70% of sun-exposed skin melanomas. In melanoma, TPMs are among the earliest mutations and can be present during the transition from nevus to melanoma. However, the specific factors that contribute to the selection of TPMs in certain nevi subsets are not well understood. To investigate this, we analyzed a group of dysplastic nevi (DN) by sequencing genes commonly mutated in melanocytic neoplasms. We examined the relationship between the identified mutations, patient age, telomere length, histological features, and the expression of p16. Our findings reveal that TPMs are more prevalent in DN from older patients and are associated with shorter telomeres. Importantly, these TPMs were not found in nevi with BRAF V600E mutations. Conversely, DN with BRAF V600E mutations were observed in younger patients, had longer telomeres and a higher proportion of p16-positive cells. This suggests that these nevi arrest growth independently of telomere shortening through a mechanism known as oncogene-induced senescence (OIS). These characteristics extend to melanoma-sequencing datasets, where melanomas with BRAF V600E mutations were more likely to have a CDKN2A inactivation, overriding OIS. In contrast, melanomas without BRAF V600E mutations showed a higher frequency of TPMs. Our data imply that TPMs are selected to bypass replicative senescence (RS) in cells that were not arrested by OIS. Overall, our results indicate that a subset of melanocytic neoplasms face constraints from RS, while others encounter OIS and RS. The order in which these barriers are overcome during progression to melanoma depends on the mutational context.

Distinct senescence mechanisms restrain progression of dysplastic nevi.

TERT promoter mutations (TPMs) are frequently found in different cancer types, including approximately 70% of sun-exposed skin melanomas. In melanoma, TPMs are among the earliest mutations and can be present during the transition from nevus to melanoma. However, the specific factors that contribute to the selection of TPMs in certain nevi subsets are not well understood. To investigate this, we analyzed a group of dysplastic nevi (DN) by sequencing genes commonly mutated in melanocytic neoplasms. We examined the relationship between the identified mutations, patient age, telomere length, histological features, and the expression of p16. Our findings reveal that TPMs are more prevalent in DN from older patients and are associated with shorter telomeres. Importantly, these TPMs were not found in nevi with BRAF V600E mutations. Conversely, DN with BRAF V600E mutations were observed in younger patients, had longer telomeres, and a higher proportion of p16-positive cells. This suggests that these nevi arrest growth independently of telomere shortening through a mechanism known as oncogene-induced senescence (OIS). These characteristics extend to melanoma sequencing data sets, where melanomas with BRAF V600E mutations were more likely to have CDKN2A inactivation, overriding OIS. In contrast, melanomas without BRAF V600E mutations showed a higher frequency of TPMs. Our data imply that TPMs are selected to bypass replicative senescence (RS) in cells that were not arrested by OIS. Overall, our results indicate that a subset of melanocytic neoplasms face constraints from RS, while others encounter OIS and RS. The order in which these barriers are overcome during progression to melanoma depends on the mutational context.

Shed syndecan-2 enhances colon cancer progression by increasing cooperative angiogenesis in the tumor microenvironment.

Although shed syndecan-2 potentiated the tumorigenic activities of colon cancer cells, how shed syndecan-2 increases this tumorigenic potential remains unclear. Using an orthotopic mouse model of colon cancer, we show that shed syndecan-2 increases colon cancer progression by cooperatively promoting angiogenesis. Co-administration with a synthetic peptide of shed syndecan-2 (S2LQ) enhanced the survival and tumor engraftment of luciferase-expressing CT26 colon adenocarcinoma cells orthotopically implanted into the cecum of BALB/c mice. Intravenous injection of S2LQ further enhanced the growth of orthotopic tumors in the cecum, with increases in the tissue infiltration of macrophages and the formation of blood vessels, mainly in peripheral layers of the tumor facing the stroma. Furthermore, S2LQ stabilized HIF1α and enhanced the VEGF expression in human colon cancer cell lines, and increased the migration of RAW 264.7 murine macrophage cells and bone marrow-derived macrophages. Finally, S2LQ increased the tube formation of vascular endothelial cells in vitro. Together, these data demonstrate that shed syndecan-2 enhances tumorigenic activity by increasing the crosstalk of cancer cells with tumor-associated macrophages and endothelial cells to enhance angiogenesis for colon cancer progression in the tumor microenvironment.

HSPB1 inhibitor J2 attenuates lung inflammation through direct modulation of Ym1 production and paracrine signaling.

Heat shock protein beta-1 (HSPB1) is a multifaceted protein that controls cellular stress, modulates cell differentiation and development, and inhibits apoptosis of cancer cells. Increased HSPB1 expression is highly associated with poor outcomes in lung cancer by enhancing cell migration and invasion; therefore, targeting HSPB1 may be a promising therapeutic for lung cancer and fibrosis. Although the HSPB1 inhibitor J2 has been reported to exhibit potent antifibrotic effects, it remains unclear whether and how J2 directly modulates inflammatory immune responses in pulmonary fibrosis. In this study, we found that J2 potently attenuated irradiation or bleomycin-induced pulmonary fibrosis by significantly inhibiting the infiltration and activation of T cells and macrophages. J2 inhibited T-cell proliferation and subsequently suppressed T helper cell development. Although there was no significant effect of J2 on cell proliferation of M1 and M2 macrophages, J2 specifically increased the expression of Ym1 in M2 macrophages without affecting the expression of other M2 markers. Interestingly, J2 increased lysosomal degradation of HSPB1 and inhibited HSPB1-induced repression of signal transducer and activator of transcription 6 (STAT6), which simultaneously increased STAT6 and Ym1 expression. Ym1 production and secretion by J2-treated M2 macrophages substantially decreased IL-8 production by airway epithelial cells in vitro and in vivo, resulting in attenuation of airway inflammation. Taken together, we suggest that J2 has potential as a therapeutic agent for pulmonary fibrosis with increased HSPB1 expression through direct immune suppression by Ym1 production by M2 macrophages as well as T-cell suppression.

dTBP2 attenuates severe airway inflammation by blocking inflammatory cellular network mediated by dTCTP.

Dimeric translationally controlled tumor protein (dTCTP), also known as histamine-releasing factor, amplifies allergic responses and its production has been shown to increase in inflammatory diseases such as allergic asthma. Despite the critical role of dTCTP in allergic inflammation, little is known about its production pathways, associated cellular networks, and underlying molecular mechanisms. In this study, we explored the dTCTP-mediated inflammatory networks and molecular mechanisms of dTCTP associated with lipopolysaccharides (LPS)-induced severe asthma. LPS stimulation increased dTCTP production by mast cells and dTCTP secretion during degranulation, and extracellular dTCTP subsequently increased the production of pro-inflammatory molecules, including IL-8, by airway epithelial cells without affecting mast cell activation. Furthermore, dimeric TCTP-binding peptide 2 (dTBP2), a dTCTP inhibitor peptide, selectively blocked the dTCTP-mediated signaling network from mast cells to epithelial cells and decreased IL-8 production through IkB induction and nuclear p65 export in airway epithelial cells. More importantly, dTBP2 efficiently attenuated LPS-induced severe airway inflammation in vivo, resulting in decreased immune cell infiltration and IL-17 production and attenuated dTCTP secretion. These results suggest that dTCTP produced by mast cells exacerbates airway inflammation through activation of airway epithelial cells in a paracrine signaling manner, and that dTBP2 is beneficial in the treatment of severe airway inflammation by blocking the dTCTP-mediated inflammatory cellular network.

Transcriptional coactivator with PDZ-binding motif stimulates epidermal regeneration via induction of amphiregulin expression after ultraviolet damage.

Ultraviolet (UV) irradiation induces the proliferation and differentiation of keratinocytes in the basal layer of the epidermis, which increases epidermal thickness in skin regeneration. However, the mechanism underlying this phenomenon is not yet known in detail. In this study, we aimed to demonstrate that the transcriptional coactivator with PDZ-binding motif (TAZ) stimulates epidermal regeneration by increasing keratinocyte proliferation. During epidermal regeneration, TAZ is localized in the nucleus of keratinocytes of the basal layer and stimulates epidermal growth factor receptor (EGFR) signaling. TAZ depletion in keratinocytes decreased EGFR signaling activation, which delays epidermal regeneration. Interestingly, TAZ stimulated the transcription of amphiregulin (AREG), a ligand of EGFR, through TEAD-mediated transcriptional activation. Together, these results show that TAZ stimulates EGFR signaling through AREG induction, suggesting that it plays an important role in epidermal regeneration.

Mutations in the promoter of the telomerase gene TERT contribute to tumorigenesis by a two-step mechanism.

TERT promoter mutations (TPMs) are the most common noncoding mutations in cancer. The timing and consequences of TPMs have not been fully established. Here, we show that TPMs acquired at the transition from benign nevus to malignant melanoma do not support telomere maintenance. In vitro experiments revealed that TPMs do not prevent telomere attrition, resulting in cells with critically short and unprotected telomeres. Immortalization by TPMs requires a gradual up-regulation of telomerase, coinciding with telomere fusions. These data suggest that TPMs contribute to tumorigenesis by promoting immortalization and genomic instability in two phases. In an initial phase, TPMs do not prevent bulk telomere shortening but extend cellular life span by healing the shortest telomeres. In the second phase, the critically short telomeres lead to genome instability and telomerase is further up-regulated to sustain cell proliferation.