α-PD-1 therapy elevates Treg/Th balance and increases tumor cell pSmad3 that are both targeted by α-TGFß antibody to promote durable rejection and immunity in squamous cell carcinomas.

BACKGROUND: Checkpoint blockade immunotherapy has improved metastatic cancer patient survival, but response rates remain low. There is an unmet need to identify mechanisms and tools to circumvent resistance. In human patients, responses to checkpoint blockade therapy correlate with tumor mutation load, and intrinsic resistance associates with pre-treatment signatures of epithelial mesenchymal transition (EMT), immunosuppression, macrophage chemotaxis and TGFß signaling. METHODS: To facilitate studies on mechanisms of squamous cell carcinoma (SCC) evasion of checkpoint blockade immunotherapy, we sought to develop a novel panel of murine syngeneic SCC lines reflecting the heterogeneity of human cancer and its responses to immunotherapy. We characterized six Kras-driven cutaneous SCC lines with a range of mutation loads. Following implantation into syngeneic FVB mice, we examined multiple tumor responses to α-PD-1, α-TGFß or combinatorial therapy, including tumor growth rate and regression, tumor immune cell composition, acquired tumor immunity, and the role of cytotoxic T cells and Tregs in immunotherapy responses. RESULTS: We show that α-PD-1 therapy is ineffective in establishing complete regression (CR) of tumors in all six SCC lines, but causes partial tumor growth inhibition of two lines with the highest mutations loads, CCK168 and CCK169. α-TGFß monotherapy results in 20% CR and 10% CR of established CCK168 and CCK169 tumors respectively, together with acquisition of long-term anti-tumor immunity. α-PD-1 synergizes with α-TGFß, increasing CR rates to 60% (CCK168) and 20% (CCK169). α-PD-1 therapy enhances CD4 + Treg/CD4 + Th ratios and increases tumor cell pSmad3 expression in CCK168 SCCs, whereas α-TGFß antibody administration attenuates these effects. We show that α-TGFß acts in part through suppressing immunosuppressive Tregs induced by α-PD-1, that limit the anti-tumor activity of α-PD-1 monotherapy. Additionally, in vitro and in vivo, α-TGFß acts directly on the tumor cell to attenuate EMT, to activate a program of gene expression that stimulates immuno-surveillance, including up regulation of genes encoding the tumor cell antigen presentation machinery. CONCLUSIONS: We show that α-PD-1 not only initiates a tumor rejection program, but can induce a competing TGFß-driven immuno-suppressive program. We identify new opportunities for α-PD-1/α-TGFß combinatorial treatment of SCCs especially those with a high mutation load, high CD4+ T cell content and pSmad3 signaling. Our data form the basis for clinical trial of α-TGFß/α-PD-1 combination therapy (NCT02947165).

Functional characterization of novel presenilin-2 variants identified in human breast cancers.

We identified in breast cancer cases two germline alterations, R62H and R71W, in presenilin-2 (PS-2), a gene involved in familial Alzheimer's disease (FAD). The role of these alleles in FAD is unclear, but neither allele affected Abeta(42)/Abeta(40) ratio. However, both R62H and R71W alterations compromised PS-2 function in Notch signaling in Caenorhabditis elegans and cell growth inhibition in mouse embryonic fibroblasts, and these effects were dependent on gene dosage. We found that both alterations enhanced the degradation of the PS-2 full-length protein, indicating that they may have a loss-of function effect. The effect of the R71W alteration was noticeably stronger, and we observed an almost threefold higher frequency of this allele in breast cancer cases versus controls, but this difference did not reach statistical significance. Nonetheless, these results collectively suggest that the novel PS-2 alleles described here, especially R71W, affect PS-2 function and may potentially confer a moderate risk of susceptibility to breast cancer.

Analysis of Craniofacial Remodeling in the Aging Midface Using Reconstructed Three-Dimensional Models in Paired Individuals.

BACKGROUND: Aging leads to a panoply of changes of facial morphology. The present study was conducted to analyze modifications of the facial skeleton with aging, using high-resolution imaging and comparing the same individuals at two time points. METHODS: The electronic medical record system was reviewed since its inception in 2001 for patients for whom two computed tomographic scans of the midface were obtained at least 9 years apart. The computed tomographic scans were converted into three-dimensional craniofacial models for each patient, using the initial and the follow-up computed tomographic scan data. The models were used to highlight areas of bone growth and bone resorption using a color scale and to perform a cephalometric analysis. RESULTS: Seven patients with a mean age of 61 years and computed tomographic scans on average 10.3 years apart were included. Bone resorption was consistently present (100 percent) at the pyriform aperture and the anterior wall of the maxilla. Resorption was noted at the superocentral (71 percent), inferolateral (57 percent), and superomedial (57 percent) aspects of the orbital rim. Resorption occurred earlier at the inferolateral orbital rim followed by the superomedial orbital rim in later decades of life. Paired-analysis of change in the orbital rim height and width demonstrated a mean decrease over time but was not significant. CONCLUSION: Bone remodeling in the same individual, over a period of 10 years, was characterized by resorption at the pyriform aperture; anterior wall of the maxilla; and superocentral, superomedial, and inferolateral aspects of the orbital rims.

Interactions between wild-type and mutant Ras genes in lung and skin carcinogenesis.

Ras oncogenes (Hras, Kras and Nras) are important drivers of carcinogenesis. However, tumors with Ras mutations often show loss of the corresponding wild-type (WT) allele, suggesting that proto-oncogenic forms of Ras can function as a suppressor of carcinogenesis. In vitro studies also suggest that WT Ras proteins can suppress the tumorigenic properties of alternate mutant Ras family members, but in vivo evidence for these heterologous interactions is lacking. We have investigated the genetic interactions between different combinations of mutant and WT Ras alleles in vivo using carcinogen-induced lung and skin carcinogenesis in mice with targeted deletion of different Ras family members. The major suppressor effect of WT Kras is observed only in mutant Kras-driven lung carcinogenesis, where loss of one Kras allele led to increased tumor number and size. Deletion of one Hras allele dramatically reduced the number of skin papillomas with Hras mutations, consistent with Hras as the major target of mutation in these tumors. However, skin carcinoma numbers were very similar, suggesting that WT Hras functions as a suppressor of progression from papillomas to invasive squamous carcinomas. In the skin, the Kras proto-oncogene functions cooperatively with mutant Hras to promote papilloma development, although the effect is relatively small. In contrast, the Hras proto-oncogene attenuated the activity of mutant Kras in lung carcinogenesis. Interestingly, loss of Nras increased the number of mutant Kras-induced lung tumors, but decreased the number of mutant Hras-induced skin papillomas. These results show that the strongest suppressor effects of WT Ras are only seen in the context of mutation of the cognate Ras protein, and only relatively weak effects are detected on tumor development induced by mutations in alternative family members. The data also underscore the complex and context-dependent nature of interactions between proto-oncogenic and oncogenic forms of different Ras family members during tumor development.

Preferential allelic expression can lead to reduced expression of BRCA1 in sporadic breast cancers.

BRCA1 is considered to be a tumor-suppressor gene, yet mutations in this gene are uncommon in sporadic breast tumors. We investigated whether mechanisms other than DNA mutations that affect the coding region might be involved in breast carcinogenesis. Since loss of expression of the BRCA1 gene would lead to lack of protein, we evaluated the level of BRCA1 mRNA in 21 normal epithelial specimens and in 74 breast carcinomas using quantitative reverse-transcription-polymerase-chain-reaction (RT-PCR). All normal breast epithelial samples expressed BRCA1 mRNA. On the other hand, the tumor specimens exhibited approximately 10-fold range of levels of BRCA1, with some specimens expressing barely detectable amounts of BRCA1 mRNA. The distribution in levels was significantly higher in normal breast epithelial cells than in tumor specimens (p = 0.004). Examination of the BRCA1 locus indicated that deletion of the BRCA1 gene may account for low levels of BRCA1 in a number of specimens. In addition, analysis of samples with relatively reduced levels of BRCA1 expression revealed preferential allele-specific expression in a number of cases, suggesting the presence of regulatory mutations. Our data suggest that the BRCA1 gene may be involved in sporadic breast carcinogenesis through a reduction in gene expression.

Analysis of mRNA from microdissected frozen tissue sections without RNA isolation.

Molecular study of gene expression in solid tumors is based largely on mRNA extracted from crushed frozen tumor samples. As most tumors are heterogeneous in composition, molecular alterations acquired by neoplastic cells may be masked by normal epithelial, stromal, and inflammatory cells, which may make up a significant volume of many tumors. We have developed a technique whereby reverse transcription polymerase chain reaction (RT-PCR) can be performed on lesions microdissected directly from frozen tumor sections. This allows for molecular analysis of mRNA from histologically homogeneous cell populations. Cryostat sections are placed onto a thin layer of 2% agarose on a glass slide and stained briefly. Microdissected tissue is immersed in a freezing solution to lyse the cells; aliquots are used directly in RT-PCR reactions without further purification. We successfully amplified cDNA fragments of the beta2-microglobulin, p21Waf1, and BRCA1 genes from small microdissected lesions. Also, we examined the effect of varying thickness of cryostat sections (20 versus 40 microm) and several tissue staining dyes. We estimate that a small microdissected region, containing no more than 200 cells, can provide enough mRNA to make cDNA for 80 to 100 PCR reactions. We believe that this technique will be a useful tool to study gene expression in histologically defined tissues.