Maja Hühns

Plastid targeting strategies for cyanophycin synthetase to achieve high-level polymer accumulation in Nicotiana tabacum

The production of biodegradable polymers in transgenic plants is an important challenge in plant biotechnology; nevertheless, it is often accompanied by reduced plant fitness. In order to decrease the phenotypic abnormalities caused by cytosolic production of the biodegradable polymer cyanophycin, and to increase polymer accumulation, four translocation pathway signal sequences for import into chloroplasts were individually fused to the coding region of the cyanophycin synthetase gene (cphA(Te)) of Thermosynechococcus elongatus BP-1, resulting in the constructs pRieske-cphA(Te), pCP24-cphA(Te), pFNR-cphA(Te) and pPsbY-cphA(Te). These constructs were expressed in Nicotiana tabacum var. Petit Havana SRI under the control of the constitutive cauliflower mosaic virus (CaMV) 35S promoter. Three of the four constructs led to polymer production. However, only the construct pPsbY-cphA(Te) led to cyanophycin accumulation exclusively in chloroplasts. In plants transformed with the pCP24-cphA(Te) and pFNR-cphA(Te) constructs, water-soluble and water-insoluble forms of cyanophycin were only located in the cytoplasm, which resulted in phenotypic changes similar to those observed in plants transformed with constructs lacking a targeting sequence. The plants transformed with pPsbY-cphA(Te) produced predominantly the water-insoluble form of cyanophycin. The polymer accumulated to up to 1.7% of dry matter in primary (T(0)) transformants. Specific T(2) plants produced 6.8% of dry weight as cyanophycin, which is more than five-fold higher than the previously published value. Although all lines tested were fertile, the progeny of the highest cyanophycin-producing line showed reduced seed production compared with control plants.

Tuber‐specific cphA expression to enhance cyanophycin production in potatoes

The production of biodegradable polymers that can be used to substitute petrochemical compounds in commercial products in transgenic plants is an important challenge for plant biotechnology. Nevertheless, it is often accompanied by reduced plant fitness. To decrease the phenotypic abnormalities of the sprout and to increase polymer production, we restricted cyanophycin accumulation to the potato tubers by using the cyanophycin synthetase gene (cphA(Te)) from Thermosynechococcus elongatus BP-1, which is under the control of the tuber-specific class 1 promoter (B33). Tuber-specific cytosolic (pB33-cphA(Te)) as well as tuber-specific plastidic (pB33-PsbY-cphA(Te)) expression resulted in significant polymer accumulation solely in the tubers. In plants transformed with pB33-cphA(Te), both cyanophycin synthetase and cyanophycin were detected in the cytoplasm leading to an increase up to 2.3% cyanophycin of dry weight and resulting in small and deformed tubers. In B33-PsbY-cphA(Te) tubers, cyanophycin synthetase and cyanophycin were exclusively found in amyloplasts leading to a cyanophycin accumulation up to 7.5% of dry weight. These tubers were normal in size, some clones showed reduced tuber yield and sometimes exhibited brown sunken staining starting at tubers navel. During a storage period over of 32 weeks of one selected clone, the cyanophycin content was stable in B33-PsbY-cphA(Te) tubers but the stress symptoms increased. However, all tubers were able to germinate. Nitrogen fertilization in the greenhouse led not to an increased cyanophycin yield, slightly reduced protein content, decreased starch content, and changes in the amounts of bound and free arginine and aspartate, as compared with control tubers were observed.

Isolation of cyanophycin from tobacco and potato plants with constitutive plastidic cphATe gene expression.

A chimeric cyanophycin synthetase gene composed of the cphATe coding region from the cyanobacterium Thermosynechococcus elongatus BP-1, the constitutive 35S promoter and the plastid targeting sequence of the integral photosystem II protein PsbY was transferred to the tobacco variety Petit Havanna SRI and the commercial potato starch production variety Albatros. The resulting constitutive expression of cyanophycin synthetase leads to polymer contents in potato leaf chloroplasts of up to 35 mg/g dry weight and in tuber amyloplasts of up to 9 mg/g dry weight. Both transgenic tobacco and potato were used for the development of isolation methods applicable for large-scale extraction of the polymer. Two different procedures were developed which yielded polymer samples of 80 and 90% purity, respectively.

Expression of young HERV-H loci in the course of colorectal carcinoma and correlation with molecular subtypes

Background Expression of the human endogenous retrovirus (HERV)-H family has been associated with colorectal carcinomas (CRC), yet no individual HERV-H locus expression has been thoroughly correlated with clinical data. Here, we characterized HERV-H reactivations in clinical CRC samples by integrating expression profiles, molecular patterns and clinical data. Expression of relevant HERV-H sequences was analyzed by qRT-PCR on two well-defined clinical cohorts (n = 139 pairs of tumor and adjacent normal colon tissue) including samples from adenomas (n = 21) and liver metastases (n = 16). Correlations with clinical and molecular data were assessed. Results CRC specific HERV-H sequences were validated and found expressed throughout CRC disease progression. Correlations between HERV-H expression and lymph node invasion of tumor cells (p = 0.0006) as well as microsatellite instable tumors (p < 0.0001) were established. No association with regard to age, tumor localization, grading or common mutations became apparent. Interestingly, CRC expressed elements belonged to specific young HERV-H subfamilies and their 5′ LTR often presented active histone marks. Conclusion These results suggest a functional role of HERV-H sequences in colorectal carcinogenesis. The pronounced connection with microsatellite instability warrants a more detailed investigation. Thus, HERV-H sequences in addition to tumor specific mutations may represent clinically relevant, truly CRC specific markers for diagnostic, prognostic and therapeutic purposes.

Biological and molecular effects of small molecule kinase inhibitors on low-passage human colorectal cancer cell lines.

Low-passage cancer cell lines are versatile tools to study tumor cell biology. Here, we have employed four such cell lines, established from primary tumors of colorectal cancer (CRC) patients, to evaluate effects of the small molecule kinase inhibitors (SMI) vemurafenib, trametinib, perifosine, and regorafenib in an in vitro setting. The mutant BRAF (V600E/V600K) inhibitor vemurafenib, but also the MEK1/2 inhibitor trametinib efficiently inhibited DNA synthesis, signaling through ERK1/2 and expression of genes downstream of ERK1/2 in BRAF mutant cells only. In case of the AKT inhibitor perifosine, three cell lines showed a high or intermediate responsiveness to the drug while one cell line was resistant. The multikinase inhibitor regorafenib inhibited proliferation of all CRC lines with similar efficiency and independent of the presence or absence of KRAS, BRAF, PIK3CA, and TP53 mutations. Regorafenib action was associated with broad-range inhibitory effects at the level of gene expression but not with a general inhibition of AKT or MEK/ERK signaling. In vemurafenib-sensitive cells, the antiproliferative effect of vemurafenib was enhanced by the other SMI. Together, our results provide insights into the determinants of SMI efficiencies in CRC cells and encourage the further use of low-passage CRC cell lines as preclinical models.

The PD-1 expressing immune phenotype of T cell exhaustion is prominent in the ‘immunoreactive’ microenvironment of colorectal carcinoma

This study was designed to test programmed cell death 1 (PD‐1) expression of T cells, the hallmark of T cell exhaustion, in different ‘immune‐classes’ of colorectal carcinoma microenvironments as delineated by unsupervised hierarchical cluster analysis.

HPV Infection, but Not EBV or HHV-8 Infection, Is Associated with Salivary Gland Tumours.

Benign and malignant salivary gland tumours are clinically heterogeneous and show different histology. Little is known about the role of human herpes virus 8 (HHV-8), Epstein-Barr virus (EBV), and human papillomavirus (HPV) infection in salivary gland neoplasms. We investigated the presence of the three viruses in formalin-fixed, paraffin-embedded tissue samples in a cohort of 200 different salivary gland tumours. We performed EBV-LMP-1 and HHV-8 and p16 immunohistochemistry, a specific chip based hybridization assay for detection and typing of HPV and a chromogenic in situ hybridization for EBV analysis. Only one case, a polymorphic low-grade carcinoma, showed HHV-8 expression and one lymphoepithelial carcinoma was infected by EBV. In 17 cases (9%) moderate or strong nuclear and cytoplasmic p16 expression was detected. The HPV type was investigated in all of these cases and additionally in 8 Warthins tumours. In 19 cases HPV type 16 was detected, mostly in Warthins tumour, adenoid cystic carcinoma, and adenocarcinoma NOS. We concluded that HHV-8 infection and EBV infection are not associated with salivary gland cancer, but HPV infection may play a role in these tumour entities.

C-kit overexpression is not associated with KIT gene mutations in chromophobe renal cell carcinoma or renal oncocytoma

INTRODUCTION C-kit overexpression has previously been described in chromophobe renal cell carcinoma (cpRCC) and renal oncocytoma (RO). However, so far no KIT mutations have been found. The objective of our study was to analyse c-kit in a large cohort of renal tumors and to perform KIT mutation analysis in a subset cpRCC and RO cases with overexpression of c-kit. MATERIALS AND METHODS We studied the immunohistochemical expression of c-kit on tissue microarrays containing formalin-fixed, paraffin-embedded samples of 948 patients with renal tumors. CpRCC and RO cases with c-kit overexpression (n=23) were analyzed for KIT mutations in exons 9, 11, 13, 14, 15, and 17. RESULTS Expression of c-kit was found in 6/642 (0.9%) clear cell RCC, 3/154 (1.9%) papillary RCC, 54/69 (78.3%) cpRCC, 37/45 (82.2%) RO and 2/30 (6.7%) of other unclassified tumor types. In none of the RO and cpRCC cases analyzed, a KIT gene mutation was found. CONCLUSION C-kit expression is found in the majority of cpRCC and RO, but these tumors do not harbor the usual c-kit activating mutations. This may have implications for the use of tyrosine kinase inhibitors in patients with advanced cpRCC and c-kit expression.

Identification of HPV Types and Mycobacterium Tuberculosis Complex in Historical Long-Term Preserved Formalin Fixed Tissues in Different Human Organs

University anatomical-pathological collections represent huge sources of human tissues and preparations from a variety of different diseases. With the help of modern genetic and histological methods, preserved fixed tissues from pathological collections can be used to re-evaluate former diagnoses. We analysed 25 specimens from our pathological collection with ages ranging from 78 to 112 years. The tissues originated from the oral cavity, lip, tongue, lung, bone, kidney, spleen, thymus, larynx, lymph node, penis and uterine cervix with an original diagnosis of epithelial cancers or tuberculosis. Amplifiable DNA was extracted and in epithelial cancers, potential HPV infection was investigated. Specimens with an original diagnosis of tuberculosis were examined for mycobacterial infection. The tissues were also examined using modern histological methods. Our data showed that in 24/25 specimens the histological structure was preserved and in 10/11 specimens the diagnosis of squamous cell carcinoma could be confirmed. Additionally, HPV type 16 was detected in 8 specimens. The histological pattern of tuberculosis was found in 11/14 specimens and the Mycobacterium tuberculosis complex was ascertained in four specimens. Our study showed that pathogens such as HPV or Mycobacterium tuberculosis can be detected in historical pathological preparations, and that these collections are suitable for further epidemiological research.

The mutational profile and infiltration pattern of murine MLH1 -/- tumors: concurrences, disparities and cell line establishment for functional analysis

Mice lines homozygous negative for one of the four DNA mismatch repair (MMR) genes (MLH1, MSH2, PMS2, MSH6) were generated as models for MMR deficient (MMR-D) diseases. Clinically, hereditary forms of MMR-D include Lynch syndrome (characterized by a germline MMR gene defect) and constitutional MMR-D, the biallelic form. MMR-D knockout mice may be representative for both diseases. Here, we aimed at characterizing the MLH1-/- model focusing on tumor-immune microenvironment and identification of coding microsatellite mutations in lymphomas and gastrointestinal tumors (GIT). All tumors showed microsatellite instability (MSI) in non-coding mononucleotide markers. Mutational profiling of 26 coding loci in MSI+ GIT and lymphomas revealed instability in half of the microsatellites, two of them (Rfc3 and Rasal2) shared between both entities. MLH1-/- tumors of both entities displayed a similar phenotype (high CD71, FasL, PD-L1 and CTLA-4 expression). Additional immunofluorescence verified the tumors’ natural immunosuppressive character (marked CD11b/CD200R infiltration). Vice versa, CD3+ T cells as well as immune checkpoints molecules were detectable, indicative for an active immune microenvironment. For functional analysis, a permanent cell line from an MLH1-/- GIT was established. The newly developed MLH1-/- A7450 cells exhibit stable in vitro growth, strong invasive potential and heterogeneous drug response. Moreover, four additional MSI target genes (Nktr1, C8a, Taf1b, and Lig4) not recognized in the primary were identified in this cell line. Summing up, molecular and immunological mechanisms of MLH1-/- driven carcinogenesis correlate well with clinical features of MMR-D. MLH1-/- knockout mice combine characteristics of Lynch syndrome and constitutional MMR-D, making them suitable models for preclinical research aiming at MMR-D related diseases.