Concordancy of immunocytochemistry profiling of circulating tumor cells with immunohistochemistry for analysis of therapeutically relevant biomarkers

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Background: Immunohistochemistry (IHC) profiling of tumor tissue is the present standard for evaluation of therapeutically relevant biomarkers such as ER, PR, HER2, AR, ARv7, PD-L1 and MMR for selection of targeted, endocrine and checkpoint inhibitor therapy selection. However, this critical analysis is dependent on availability of tumor tissue obtained by an invasive biopsy. Challenges to this analysis include insufficient tumor tissue and inability to perform a repeat biopsy to obtain fresh tumor tissue. We have previously described an approach for negative enrichment of Circulating Tumor Cells (CTCs) from peripheral blood and for Immunocytochemistry (ICC) profiling of these CTCs for detection of diagnostically relevant tissue of origin and subtype specific markers, concordant with tumor tissue analysis. Methods: In the present study, we determined concordance between tumor tissue (HPE) and CTCs (ICC) for ascertaining the status of therapeutically relevant markers ER, PR, HER2, AR, ARv7 PD-L1 and MMR. We evaluated 201 matched pairs of tumor tissue (FFPE blocks) and CTCs obtained from peripheral blood. Results: Among the 743 paired assays on matched tumor tissue and CTCs, concordance (positive or negative) was observed in 651 matched pairs (87.6%). The concordance was 82.9% for ER, 100% for PR, 90.2 % for Her2, 93.8% for AR, 90% for Arv7, 85.1% and 87.6% for PD-L1 clones 22c3 and 28-8, and 85.6% for MMR (MLH1, MSH2, MSH6, and PMS2). Conclusions: The study findings indicate that ICC analysis of CTCs may be able to substitute IHC analysis of tumor tissue for profiling of therapeutically relevant markers. This approach may have application in cases where tumor tissue may be limiting and / or where an invasive biopsy to obtain tumor tissue may be unviable.

Analytical and clinical validation of the TruCheck platform for diagnostic triaging of symptomatic cases suspected of colorectal cancer

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Background: Trucheck is a non-invasive approach for diagnostic triaging of symptomatic individuals who are suspected of Colorectal Cancer (CRC) and have been advised an invasive biopsy. Trucheck evaluates blood samples for presence of Circulating Ensembles of Tumor Associated Cells (C-ETACs: EpCAM+, Pan-CK+, CD45±) originating from a primary Colorectal Adenocarcinoma (CR-AD: CDX-2, CK-20, Muc2); such C-ETACs are unexpected in asymptomatic individuals as well as in individuals with benign Colorectal conditions. Methods: For Analytical Validation, spike-recovery analysis was performed using control cells / cell lines for EpCAM (SKBR-3), Pan-CK (SKBR-3), CD45 (PBMCs), CDX2 (CaCO2), CK20 (HCT15) and MUC2 (SW620) to determine the Sensitivity, Specificity, Accuracy, Limit of Detection, Linearity and Precision. Clinical Validations were performed using 15 mL blood samples from 587 participants. An initial Retrospective Clinical Pre-validation was based on blood samples from 350 known cases of CR-AD and 20 cases of non-CRC. The Prospective Clinical Validation was performed on blood samples collected prior to any invasive procedures from 217 symptomatic cases suspected of CRC. Results: Analytical Validation indicated 100% Sensitivity, 100% Specificity, 100% Accuracy, 90% Precision and significant linearity (R2≥0.98) for all ICC markers. Clinical Pre-validation indicated 84.9 % Sensitivity and 100% Specificity for CR-AD v/s non-CRC. In the Prospective Clinical Validation cohort, histopathological evaluation (HPE) of biopsied tumor tissue indicated benign Colorectal conditions in 10 cases and CR-AD 207 of the 217 suspected cases. Based on HPE as the standard, the Trucheck approach had 90.3% Sensitivity, 100% Specificity and 95.2% Accuracy. Conclusions: Symptomatic individuals suspected of CRC may benefit from the sensitive and specific non-invasive Trucheck approach. Individuals positive for CR-AD-specific C-ETACs can be prioritized for further clinical procedures while C-ETAC negative individuals can be considered for alternate diagnoses. The Trucheck approach can eliminate the need for (and risks associated with) invasive colon biopsies in a significant proportion of suspected cases and is especially useful where

Multi-analyte interrogation based treatment of advanced refractory cancers

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Background: Treatment of advanced refractory cancers face challenges in non-availability of systemic therapy regimens with evidenced benefit. Post failure of two to three lines of systemic treatments, patients with such cancers are usually considered for palliation or clinical trials. Prior attempts at label-agnostic treatment regimens (precision medicine) in such populations were largely based on a single-indication-single-drug paradigm which had limited application. We hypothesized that advanced refractory malignancies have latent vulnerabilities which can be identified by an integrational multi-analyte interrogation of the tumor, and can be targeted using patient-specific combination regimens to yield clinical benefit. Methods: Fresh tumor tissue and blood samples were obtained from 158 patients with solid organ cancers where the disease had progressed following failure of at least two lines of standard of care systemic treatment options. These samples were used for Encyclopedic Tumor Analysis (ETA) which interrogated gene mutations, gene overexpression, pathway dysregulation, immunohistochemistry as well as in vitro chemosensitivity profiling of viable tumor cells. Integration of datasets from the multi-analyte ETA was used to generate patient-specific therapy recommendations. Patients who received ETA-guided treatments were followed up and response to treatment was retrospectively evaluated from radiological scans. Results: All patients received ETA-guided individualized treatments which were combinations of cytotoxic, targeted and endocrine agents. No two patients received the same treatment regimen. Complete or Partial Response (CR or PR) was observed in 76 patients yielding an Objective Response Rate (ORR) of 48.1%. 67 patients showed Stable Disease (SD), thus yielding a Disease Control Rate (DCR) of 90.5%. Median Progression Free Survival (PFS) was 117 days (Range 27 – 379 days). There were no Grade IV therapy related Adverse Events or therapy related deaths. Conclusions: Viable efficacious combination treatment options can be made available for patients with advanced refractory malignancies via ETA, despite perceived non-availability or non-viability of standard of care treatment options.

Circulating microtumors: A functional hallmark for cancer detection and management

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Background: There are presently no accepted non-invasive means for detection of cancers in asymptomatic individuals or suspected cases. Radiological and serological investigations, though non-invasive, are not confirmatory and necessitate an invasive biopsy to establish malignant status of suspected findings. Invasive biopsies, in turn, face challenges due to non-representative tumor tissue or in cases where biopsy is impossible or unviable. We hypothesized that Circulating Microtumors (also called as C-ETACs: Circulating Ensembles of Tumor Associated Cells) in peripheral blood are universally present in solid organ cancers and their detection can be linked to malignant status. Methods: We obtained peripheral blood from 14,138 patients with various solid organ cancers as well as 10,625 asymptomatic individuals with age associated elevated risk of cancer. Out of the 14,138 patients with cancer, 25.1 % had local (non-metastatic) disease and 56.4% had metastatic disease as confirmed by radiological evaluation. C-ETACs were enriched and harvested from PBMCs using an epigenetically activating medium that is cytotoxic towards non-malignant epithelial and hematolymphoid cells in blood but confers survival benefit on apoptosis resistant circulating cells of tumorigenic origin and their heterotypic clusters (C-ETACs) in peripheral blood. Viable C-ETACs were identified and further characterized by immunocytochemistry (ICC) profiling. Results: C-ETACs were detected in 89.7% of samples from solid organ cancers irrespective of stage, treatment or present radiological status. C-ETACs were rarely detected (3.0%) in asymptomatic individuals. The asymptomatic individuals where C-ETACs were detected are being followed up periodically so as to enable detection of cancer based on clinical or radiological manifestation of symptoms. Conclusions: C-ETACs are ubiquitous in cancers and unexpected in asymptomatic individuals. Detection of C-ETACs in asymptomatic individuals may be indicative of risk of latent undiagnosed malignancy. The non-invasiveness of this approach makes it convenient for screening large populations for cancer.

Liquid biopsies to enable non-invasive real-time functional chemoresistance profiling in solid organ cancers

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Background: Despite the development of targeted therapy agents and immune checkpoint inhibitors (ICI), cytotoxic anticancer agents remain the mainstay of treatment in several solid organ cancers. However, instances of innate and acquired resistance towards these anticancer agents can lead to treatment failures, which remain undetectable until clinical or radiological manifestation of symptoms suggestive of disease progression. There are presently no viable means or markers to detect or monitor for chemoresistance in real time. Owing to this unmet need, cancer treatment strategies face risks of failure and poor outcomes. Methods: We obtained 15 mL blood from 3,662 patients with various solid organ cancers, of various states and including treatment-naïve and pretreated patients. Circulating Tumor Associated Cells (C-TACs) were enriched and harvested from PBMCs using an epigenetically activating medium that is cytotoxic towards non-malignant epithelial and hematolymphoid cells in blood, but confers survival benefit on apoptosis resistant cells of tumorigenic origin (Circulating Tumor Associated Cells, C-TACs). In a subset of patients, fresh tumor tissue was also obtained from which viable tumor derived cells (TDCs) were obtained. Viable TDCs and C-TACs were treated with a panel of anticancer agents and the surviving cell fraction estimated to determine chemoresistance. Results: Among the 1,325 therapy naïve patients, resistance towards treatment agents was observed in C-TACs from 56.3 % of samples. Among 2,201 pretreated patients’ samples, resistance towards treatment agents was observed in C-TACs from 77.8% of samples. The increased resistance in C-TACs from pretreated patients indicated that the C-TACs had been resistance-educated by prior therapies. In a subset of patients, Chemoresistance profile of C-TACs was observed to be 96.9% concordant with that of tumor derived cells (TDCs) which were concurrently obtained from tumor tissue indicating that C-TACs accurately represent chemo-antecedents of the tumor. Conclusions: Non-invasive chemoresistance profiling of C-TACs is a viable strategy to monitor treatment efficacy in real time. Adoption of this strategy in the clinic will not only guide treatment selection with reduced risk of failure, but will also enable timely therapeutic course correction upon detection of acquired chemoresistance.

Multi-analyte liquid biopsies based treatment in advanced refractory cancers

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Background: Tumor tissue profiling following invasive biopsies is presently the standard approach for indication-based therapy management in solid organ cancers. However, challenges in biopsy are traditionally described due to proximity to vital organs, or patients’ co-morbidities or unwillingness for an invasive procedure. Liquid biopsies for evaluation of cancers are also largely restricted to single gene testing for selection of targeted therapy agents. We developed a comprehensive liquid biopsy based multi-analyte (molecular and functional) investigation of the cancer (eLBx: Encyclopedic Liquid Biopsy) for selection and management of individualised treatments in a cohort of advanced refractory cancers. Methods: We obtained 20 mL blood from 65 patients with solid organ cancers where the disease had progressed following failure of at least two lines of systemic therapies and where biopsy to obtain tumor tissue for molecular profiling of tumor was unviable. Cell free tumor DNA (ctDNA) was interrogated for mutations, while exosomal mRNA was profiled for gene expression. Viable circulating tumor associated cells (C-TACs) were tested in vitro for chemoresistance and used to determine expression of cell surface signalling receptors by immunocytochemistry (ICC). The findings were integrated to generate patient-specific treatment regimens. In patients who received treatment, response was determined radiologically. Results: Fifty-one patients received eLBx-guided personalized treatments with combinations of cytotoxic, targeted and endocrine agents. No two patients received the same treatment regimen. Forty-three patients were evaluable for treatment response per protocol among whom Partial Response (PR) was observed in 14 patients yielding an Objective Response Rate (ORR) of 32.6%. Additionally, 23 patients showed Stable Disease thus yielding an overall Disease Control rate of 86.1%. Median Progression Free Survival (PFS) was 108 days. There were no Grade IV therapy related Adverse Events or therapy related deaths. Conclusions: The ability to make informed treatment choices from a convenient blood draw implies a reduced dependence on invasive biopsies for disease management. We demonstrate successful management of advanced refractory solid tumor malignancies using an integrational non-invasive multi-analyte liquid biopsy approach. Clinical trial information: CTRI/2019/02/017548.

Circulating ensembles of tumor-associated cells in genitourinary cancers

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Background: Detection of genitourinary cancers is based on histopathological analysis of tumor tissue obtained by invasive biopsies following manifestation of clinical or radiological symptoms. There is presently no non-invasive blood-based test with high specificity and sensitivity for detection of genitourinary cancers. Considering that unprovoked thromboembolism is a significant risk in multiple cancers, we hypothesized that tumor derived circulating emboli in peripheral blood could comprise cancer cells and would serve as a reliable biomarker for detection of genitourinary cancers. These Circulating Ensembles of Tumor Associated Cells (C-ETACs) are defined as clusters of 3 or more cells of tumorigenic origin (EpCAM+, CK+ and CD45±). Methods: We obtained 15ml of blood from 8828 individuals, including 103 cases of Renal cancer, 79 cases of bladder cancer, 153 cases of prostate cancers as well as from 8493 asymptomatic individuals with age related elevated risk and were negative in various screening investigations (CEA, AFP, CA19-9, CA125, PSA, LDCT, Mammography, PAP Smear). PBMC were isolated by centrifugation. C-ETACs were enriched, harvested and characterized by immunofluorescence staining for EpCAM, CK, CD45 as well as organ specific markers for renal, bladder and prostate cancers. Results: C-ETACs were detected in 87 (84.5%) of 103 renal cancers, 71 (89.9%) of 79 bladder cancers and 138 (90.2%) of 153 prostate cancers respectively irrespective of extent (stage / metastatic status) of disease and prior treatments. Overall sensitivity among 335 cancer patients was 88.4%. Among the 8493 asymptomatic individuals, C-ETACs were detected in 255 individuals (97% specificity). Conclusions: C-ETACs were ubiquitously detected in cancers of Kidney, Bladder and Prostate regardless of stage and treatment status, and pose significant latent risk of metastasis/recurrence. The relative undetectability of C-ETACs in the asymptomatic cohort indicates causative connection with malignancies and are hence suitable for screening for these cancers.

PD-L1 profiling of circulating tumor cells for immune checkpoint inhibitor therapy in head and neck cancers

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Background: Selection of Immune Checkpoint Inhibitor (ICI) therapies in Head and Neck cancers are based on IHC based detection of PD-L1 expression in tumor tissue. Invasive biopsy to obtain tumor tissue for IHC is associated with procedural risks, sequelae and expenses. Prior efforts at PD-L1 profiling of Circulating Tumor Cells (CTCs) have been constrained by low CTC yields. We employed a novel approach for harvesting sufficient CTCs from Head and Neck cancers that permit PD-L1 profiling by Immunocytochemistry (ICC). Methods: 15 ml peripheral blood was collected from 95 patients with head and neck squamous cell carcinomas (HNSCC). CTCs were enriched from PBMCs via an epigenetically acting stabilization process which induced apoptosis in non-malignant cells and conferred survival privilege on apoptosis-resistant CTCs, which were harvested and confirmed by immunostaining for EpCAM and pan-CK. Deep ICC profiling of CTCs was performed with organ-specific markers as well as PD-L1:22c3 and PD-L1:28-8 clones. Results: Viable CTCs could be enriched and harvested in 90 out of 95 samples (95.3%) regardless of metastatic or treatment status. Deep ICC and PD-L1 profiling could be performed in all 90 samples (100%). PD-L1 expression was quantitatively assigned as ‘Low’, ‘Moderate’ or ‘High’. 28 (31.1%) samples were positive for PD-L1:28-8 (27 Low + 1 Moderate) and 26 (28.9%) samples were positive for PD-L1:22c3 (24 Low + 2 Moderate). 15 samples were positive for both PD-L1 clones. Conclusions: CTCs in Head and Neck squamous cell carcinomas can be considered for evaluating PD-L1 expression in patients where ICI therapies are otherwise viable.

PD-L1 profiling of circulating tumor cells for immune checkpoint inhibitor therapy in gastroesophageal cancers

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Background: Selection of Immune Checkpoint Inhibitor (ICI) therapies in Gastroesophageal cancers are based on IHC based detection of PD-L1 expression in tumor tissue. Invasive biopsy to obtain tumor tissue for IHC is associated with procedural risks, sequelae and expenses. Prior efforts at PD-L1 profiling of Circulating Tumor Cells (CTCs) have been constrained by low CTC yields. We employed a novel approach for harvesting sufficient CTCs from Gastroesophageal cancers that permit PD-L1 profiling by Immunocytochemistry (ICC). Methods: 15 ml peripheral blood was collected from 106 patients among whom 20 were diagnosed with gastric adenocarcinomas (AD) and 86 with either esophageal AD or esophageal squamous cell carcinomas (SCC). CTCs were enriched from PBMCs via an epigenetically acting stabilization process which induced apoptosis in non-malignant cells and conferred survival privilege on apoptosis-resistant CTCs, which were harvested and confirmed by immunostaining for EpCAM and pan-CK positivity. Deep ICC profiling of CTCs was performed with organ-specific markers as well as PD-L1:22c3 and PD-L1:28-8 clones. Results: Viable CTCs could be enriched and harvested in 103 out of 106 samples (97.2%) regardless of metastatic or treatment status. Deep ICC and PD-L1 profiling could be performed in all 103 samples (100%). PD-L1 expression was quantitatively assigned as ‘Low’, ‘Moderate’ or ‘High’. Among the 19 gastric ADs, 5 (26.3%) samples were positive for PD-L1:22c3 and 2 (10.5%) were positive for PD-L1:28-8; all gastric ADs were ‘Low’ for either PD-L1 subtype. Among the 84 esophageal carcinomas (AD+SCC), 32 samples (38.1%) were positive for PD-L1:22c3 (26 Low + 5 Moderate + 1 High) and 16 (19.1%) were positive for PD-L1:28-8 (11 Low + 5 Moderate). Conclusions: CTCs in Gastroesophageal cancers can be considered for evaluating PD-L1 expression in patients where ICI therapies are otherwise viable.

Tumor infiltrating lymphocytes show in vitro cytotoxic activity against tumor cells in multiple cancers

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Background: There has been considerable research interest in recruiting immune cells of cancer patients to detect and destroy malignant cells. Various approaches have been attempted including activation of dendritic cells, chimeric antigen receptor T-cells, use of check point inhibitors and expansion and infusion of Tumor Infiltration Lymphocytes (TILs). TILs have however been successfully evaluated in only a few cancers such as Melanoma and Cervix. In order to explore the feasibility of using TILs for treatment of various solid organ cancers we hypothesized that their in vitro evaluation would establish preliminary viability of the approach. Methods: We isolated TILs from 3 patients with Ca Buccal Mucosa, 2 patients with Ca Cervix, 2 patients with Ca Breast and 1 patient each with Ca Bladder and Basal Cell Carcinoma. The explant cultures of primary/metastatic tumor tissues sections of minimum 3 mm3 size using appropriate growth medium in presence of T cell growth factor, interleukin 2 (IL2) was utilized for the propagation of TILs. TILs were expanded in meaningful numbers within three to four weeks of culture and characterized for in vitro cytotoxicity by live cell imaging and Interferon gamma release ((IGR) test. TCR gene repertoire sequencing was performed using Next Generation Sequencing (NGS) to accurately measure T cell diversity and clonal expansion. Results: TILs were isolated from 10 out of 10 patients with median number of TILs of 10 million / tissue section. The flow cytometric analysis revealed and confirmed the presence of various T cell markers in the TIL cultures generated. In vitro cytotoxicity analysis performed by live cell imaging and IGRs revealed high potency for tumor cell kill rate for the expanded TILs. TCR gene sequencing revealed clonal expansion in the TIL explant population. Conclusions: This study shows feasibility of TIL expansion from cohort of patients with multiple cancer types which can be utilized for large scale expansion and infusion in future clinical trials.

Clinical efficacy of combination therapies with androgen receptor antagonists for treatment of multiple refractory cancers

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Background: Androgen Receptor (AR) antagonists have been the mainstay of prostate cancer treatments. However, there is increasing interest in the use of anti-AR agents in treatment of other cancers such as Triple Negative Breast Cancer and Lung Cancer. AR antagonists are usually administered as single agents and rarely in combination with other cytotoxic or targeted agents. We hypothesized that administration of AR antagonists indicated by Encyclopedic Tumor Analysis (ETA) in synergistic combination with cytotoxic, targeted or other endocrine agents may afford clinical benefit for refractory cancers. Methods: We evaluated treatment response in a basket of 18 patients with various advanced refractory solid organ malignancies, who received personalized treatments based on ETA investigations. As part of ETA, freshly biopsied tumor tissue and blood samples were evaluated for various markers such as gene mutations (DNA), gene expression (RNA) and receptor proteins (immunohistochemistry). Finally, viable tumor cells from the freshly biopsied tissue were used in in vitro chemosensitivity analysis with a panel of cytotoxic and targeted therapy agents. Radiological disease status was evaluated retrospectively and treatment response as well as Progression Free Survival (PFS) was determined. Results: Among the 18 patients, there were 8 males (44%) and 10 females (56%) with median age of 58 years (range 28 – 79). Patients had received a median of 3 prior lines of treatment (range 1 – 14). All 18 patients received ETA guided combination treatments which included an AR blockade. 9 patients showed Partial Response ( PR) with an Objective Response Rate (ORR) of 50%. 5 patients (28%) showed stable disease for ≥3 months (Clinical Benefit Rate = 77.8%), while 4 patients (22%) showed disease progression. In 2 patients (11%) disease progressed at ~60 days and in the remaining 2 patients (11%) progression was seen at > 120 days. Treatments were well tolerated without severe adverse events. Conclusions: Androgen addicted, refractory solid organ tumors respond to combinations of cytotoxic, targeted and endocrine agents along with AR antagonists guided by ETA.

Promoter analysis of the fish gene of slow/cardiac-type myosin heavy chain implicated in specification of muscle fiber types

Vertebrate skeletal muscles consist of heterogeneous tissues containing various types of muscle fibers, where specification of the fiber type is crucial for muscle development. Fish are an attractive experimental model to study the mechanisms of such fiber type specification because of the separated localization of slow and fast muscles in the trunk myotome. We examined regulation of expression of the torafugu gene of slow/cardiac-type myosin heavy chain, MYH _M5 , and isolated an operational promoter in order to force its tissue-specific expression across different fish species via the transgenic approach in zebrafish and medaka. This promoter activity was observed in adaxial cell-derived superficial slow muscle fibers under the control of a hedgehog signal. We also uncovered coordinated expression of MYH _M5 and Sox6b, which is an important transcriptional repressor for specification of muscle fiber types and participates in hedgehog signaling. Sequence comparison in the 5'-flanking region identified three conserved regions, CSR1-CSR3, between torafugu MYH _M5 and its zebrafish ortholog. Analysis of deletion mutants showed that CSR1 significantly stimulates gene expression in slow muscle fibers. In contrast, deletion of CSR3 resulted in ectopic expression of a reporter gene in fast muscle fibers. CSR3 was found to contain a putative Sox family protein-binding site. These results indicate that the dual mechanism causing inhibition in fast muscle fibers and activation in slow muscle fibers is essential for slow muscle fiber-specific gene expression in fish.

The expression of multiple myosin heavy chain genes during skeletal muscle development of torafugu Takifugu rubripes embryos and larvae

In vertebrates, the development-dependent and tissue-specific expression of myosin heavy chain (MYH) genes (MYHs) contributes to the formation of diverged muscle fiber types. The expression patterns of developmentally regulated MYHs have been investigated in certain species of fish. However, the expression profiles of MYHs during torafugu Takifugu rubripes development, although extensively studied in adult tissues, have not been sufficiently studied, and also the expression orders of MYHs during development have remained unclear. In the present study, we comprehensively cloned four MYHs (MYH(M743-2), MYH(M86-2), MYH(M5) and MYH(M2126-1)) from embryos, and two MYHs (MYH(M2528-1) and MYH(M1034)) from larvae, and characterized their expression pattern in relation to developmental stages of torafugu by reverse transcription (RT)-PCR and in situ hybridization. The expression of MYHs from torafugu embryos and larvae appeared sequentially and varied largely in relation to the developmental stage-dependent and fibers-type-specific manners. The transcripts of MYH(M743-2) appeared first in embryos at 3 days post fertilization (dpf) and were localized in the epaxial and hypaxial domains of fast muscle fibers of larval myotome, whereas those of MYH(M5) and MYH(M86-2) in 3 dpf and 4 dpf, respectively, and both were localized in superficial slow and horizontal myoseptum regions. The expression of MYH(M1034) and MYH(M2126-1) was quite low and mostly undetectable. Different MYHs from torafugu embryos and larvae have also been found to be expressed differentially in pectoral fin and craniofacial muscles. Interestingly, the transcripts of MYH(M2528-1) first appeared at 6 dpf and were distinctly expressed at the dorsal and ventral extremes of larval myotome, suggesting its involvement in stratified hyperplasia. The novel involvement of MYH(M2528-1) in mosaic hyperplasia was further confirmed in juvenile torafugu, where the transcripts were expressed in fast fibers with small diameters as well as the inner part of superficial slow fibers.

Cloning, expression, and localization of two types of fast skeletal myosin heavy chain genes from black tiger and Pacific white shrimps

The physiology and biochemistry of skeletal muscles in shrimps have been poorly understood compared with those from vertebrates. The present study was conducted focusing on myosin, the major protein in skeletal muscle, from adult specimens of black tiger Penaeus monodon and Pacific white Penaeus vannamei shrimps. Two genes encoding myosin heavy chain (MHC), a large subunit of the myosin molecule, were cloned from abdominal fast skeletal muscle and defined as MHCa and MHCb according to our previous study on kuruma shrimp Marsupenaeus japonicus. Random cloning demonstrated that the MHCb gene (MHCb) was expressed more abundantly than MHCa. The full-length cDNA clones of MHCa and MHCb from black tiger shrimp consisted of 5,926 and 5,914 bp, respectively, which encoded 1,914 and 1,909 amino acids, respectively, whereas those from Pacific white shrimp consisted of 5,923 and 5,908 bp, respectively, which encoded 1,913 and 1,909 amino acids, respectively. Both MHCa and MHCb were considered to be fast muscle type due to their strict localization in fast muscle. The amino acid identities between MHCa and MHCb of black tiger shrimp were 77%, 60%, and 73% in the regions of subfragment-1 (S1), subfragment-2 (S2) and light meromyosin (LMM), respectively, with 71% in total, whereas those of Pacific white shrimp were 78%, 60%, and 73% in the regions of S1, S2, and LMM, respectively, with 72% in total. In situ hybridization and northern blot analysis using different regions from abdominal muscle demonstrated different localizations of MHCa and MHCb transcripts in this muscle, suggesting their distinct physiological functions.

The occurrence of two types of fast skeletal myosin heavy chains from abdominal muscle of kuruma shrimp Marsupenaeus japonicus and their different tissue distribution

Shrimps belong to the class Crustacea, which forms a large, diverse group in the invertebrates. However, the physiology and biochemistry of their skeletal muscles have been poorly understood compared with those from vertebrates including mammals and fish. The present study focused on myosin, the major protein in skeletal muscle, from adult specimens of kuruma shrimp Marsupenaeus japonicus. Two types of the gene encoding myosin heavy chain (MHC), a large subunit of the myosin molecule, were cloned from abdominal fast skeletal muscle and defined as MHCa and MHCb. Protein analysis revealed that the MHCa isoform was expressed at a higher level than the MHCb isoform. The full-length cDNA clones of MHCa and MHCb consisted of 5929 bp and 5955 bp, respectively, which encoded 1912 and 1910 amino acids, respectively. Both were classified into fast muscle type by comparison with the partially deduced amino acid sequences of fast-type and slow-type (S(1), slow twitch) MHCs reported previously for the American lobster Homarus americanus. The amino acid identities between MHCa and MHCb of kuruma shrimp were 78%, 60% and 72% in the regions of subfragment-1, subfragment-2 and light meromyosin, respectively, and 71% in total. In situ hybridisation using anti-sense RNA-specific probes, along with northern blot analysis using different tissues from abdominal muscle, revealed the different localisation of MHCa and MHCb transcripts in abdominal fast skeletal muscle, suggesting their distinct physiological functions.

A 5'-flanking region of embryonic-type myosin heavy chain gene, MYH(M)₇₄₃₋₂, from torafugu Takifugu rubripes regulates developmental muscle-specific expression

The myosin heavy chain gene, MYH(M)₇₄₃₋₂, is highly expressed in fast muscle fibers of torafugu embryos. However, the regulatory mechanisms involved in its expression have been unclear. In this study, we examined spatio-temporal expression patterns of this gene during development by injecting expression vectors containing the GFP reporter gene fused to the 5'-flanking region of MYH(M)₇₄₃₋₂ into fertilized eggs of zebrafish and medaka. Although the -2.1kb 5'-flanking region of torafugu MYH(M)₇₄₃₋₂ showed no homology with the corresponding regions of zebrafish and medaka orthologous genes on the rVISTA analysis, the torafugu 5'-flanking region activated the GFP expression which was detected in the myotomal compartment for both zebrafish and medaka embryos. The GFP expression was localized to fast and slow muscle fibers in larvae as revealed by immunohistochemical analysis. In addition to the above tissues, GFP was also expressed in jaw, eye and pectoral fin muscles in embryos and larvae. These results clearly demonstrated that the 2.1 kb 5'-flanking region of MYH(M)₇₄₃₋₂ contains essential cis-regulatory sequences for myogenesis that are conserved among torafugu, zebrafish and medaka.

Fibre type-specific expression patterns of myosin heavy chain genes in adult torafugu Takifugu rubripes muscles

Comprehensive in silico studies, based on the total fugu genome database, which was the first to appear in fish, revealed that torafugu Takifugu rubripes contains 20 sarcomeric myosin heavy chain (MYH) genes (MYH genes) (Ikeda et al., 2007). The present study was undertaken to identify MYH genes that would be expressed in adult muscles. In total, seven MYH genes were found by screening cDNA clone libraries constructed from fast, slow and cardiac muscles. Three MYH genes, fast-type MYH(M86-1), slow-type MYH(M8248) and slow/cardiac-type MYH(M880), were cloned exclusively from fast, slow and cardiac muscles, respectively. Northern blot hybridization substantiated their specific expression, with the exception of MYH(M880). In contrast, transcripts of fast-type MYH(M2528-1) and MYH(M1034) were found in both fast and slow muscles as revealed by cDNA clone library and northern blot techniques. This result was supported by in situ hybridization analysis using specific RNA probes, where transcripts of fast-type MYH(M2528-1) were expressed in fast fibres with small diameters as well as in fibres of superficial slow muscle with large diameters adjacent to fast muscle. Transcripts of fast-type MYH(M86-1) were expressed in all fast fibres with different diameters, whereas transcripts of slow-type MYH(M8248) were restricted to fibres with small diameters located in a superficial part of slow muscle. Interestingly, histochemical analyses showed that fast fibres with small diameters and slow fibres with large diameters both contained acid-stable myofibrillar ATPase, suggesting that these fibres have similar functions, possibly in the generation of muscle fibres irrespective of their fibre types.