There are several mechanisms by which the aging microenvironment can drive cancer and influence response to therapy, according to a plenary presentation at the.
, highlighted research showing how the aging microenvironment affects tumor cell metabolism, angiogenesis, and treatment resistance in melanoma.
Dr. Weeraratna, of Johns Hopkins Bloomberg School of Public Health in Baltimore, first described a study showing how fibroblasts in the aged microenvironment contribute to tumor progression in models of melanoma ().
Dr. Weeraratna and colleagues isolated dermal fibroblasts from young human donors (aged 25-35 years) and older donors (55-65 years) and used these cells to produce artificial skin.
Melanoma cells placed in the artificial skin created with young fibroblasts remained “very tightly nested at the surface,” Dr. Weeraratna said. On the other hand, melanoma cells migrated “very rapidly” through the artificial dermis created from aged fibroblasts.
In mouse models of melanoma, tumors grew much faster in young mice (6-8 weeks) than in old mice (12-18 months). However, tumors metastasized to the lung at a “much greater rate in the aged mice than in the young mice,” Dr. Weeraratna said.
Angiogenesis, SFRP2, and VEGF
Dr. Weeraratna went on to explain how a member of her lab conducted proteomic analyses of young and aged lung fibroblasts. The results were compared with results from prior analyses of young and aged skin fibroblasts.
The results showed that aged skin fibroblasts promote noncanonical WNT signaling via expression of SFRP2, SERPINE2, DKK1, Wnt5A, and ROR2. On the other hand, aged lung fibroblasts promote canonical WNT signaling via some of the same family members, including SFRP1, DKK3, and ROR1.
Research by another group showed that SFRP2 stimulates angiogenesis via a calcineurin/NFAT signaling pathway ().
Research in Dr. Weeraratna’s lab showed that SFRP2 and VEGF are inversely correlated with aging. Tumors in aged mice had an abundance of SFRP2 but little VEGF. Tumors in young mice had an abundance of VEGF but little SFRP2.
Dr. Weeraratna’s team wanted to determine if results would be similar in melanoma patients, so the researchers analyzed data from the TCGA database. They found that VEGF and two of its key receptors are decreased in older melanoma patients, in comparison with younger melanoma patients.
The clinical relevancy of this finding is reflected in an analysis of data from the AVAST-M study (). When compared with observation, bevacizumab did not improve survival overall or for older patients, but the EGFR inhibitor was associated with longer survival in patients younger than 45 years.
Dr. Weeraratna said this finding and her group’s prior findings suggest younger melanoma patients have more VEGF but less angiogenesis than older patients. The older patients have less VEGF and more SFRP2, which drives angiogenesis.
Dr. Weeraratna’s lab then conducted experiments in young mice, which suggested that an anti-VEGF antibody can reduce angiogenesis, but not in the presence of SFRP2.