Diagnostic molecular pathology: current techniques and clinical applications, part I

Lacunae in Laboratory Medicine Services and in Pathology Education in Medical Schools in India

CONTEXT.—

Laboratories of many medical college hospitals in India do not offer important diagnostic tests, most of which are routine in the West. This detracts from the service as well as the educational function of the college.

OBJECTIVES.—

To provide the background to pathology and laboratory medicine services and education in India, and to create a questionnaire that will put the lack of tertiary care laboratory services in perspective. This article will help illustrate the lacunae in laboratory medicine services and in the education of students. For this, we present information on the health services and pathology education facilities in India. We propose a questionnaire comprising 30 questions in various disciplines in pathology and laboratory medicine. These questions will help administrators and bureaucrats evaluate the status of the laboratories with respect to the services provided.

DATA SOURCES.—

Sources include Web sites of the government of India, including that of the National Accreditation Board for Testing and Calibration Laboratories; indexed medical journal articles; and standard books and white papers on health care in India. We also used our personal experiences and interpretations of the laboratory and medical education sector in India.

CONCLUSIONS.—

Medical colleges in India need to offer specialized diagnostic services if they are to achieve the targets of universal health care as well as turning out competent doctors. The agencies responsible for health care in India should use the questionnaire as a first step toward improving laboratory services. Other low- and middle-income countries should also adopt this method.

A call to action: molecular pathology in Brazil

Background

Adoption of molecular pathology in Brazil is currently very limited. Of note, there are no programs for training new molecular pathologists in the country; thus, documents compiling nationally applicable information on molecular pathology are few.

Methods

A selected panel of Brazilian experts in fields related to molecular pathology were provided with a series of relevant questions to address prior to the multi-day conference. Within this conference, each narrative was discussed and edited by the entire group, through numerous drafts and rounds of discussion until a consensus was achieved.

Results

The panel proposes specific and realistic recommendations for implementing molecular pathology in cancer care in Brazil. In creating these recommendations, the authors strived to address all barriers to the widespread use and impediments to access mentioned previously within this manuscript.

Conclusion

This manuscript provides a review of molecular pathology principles as well as the current state of molecular pathology in Brazil. Additionally, the panel proposes practical and actionable recommendations for the implementation of molecular pathology throughout the country in order to increase awareness of the importance molecular pathology in Brazil.

Molecular Methods: Clinical Utilization and Designing a Test Menu

Pre-analytical factors in molecular oncology diagnostics are reviewed. Issues around sample collection, storage, and transport that might affect the stability of nucleic acids and the ability to perform molecular testing are addressed. In addition, molecular methods used commonly in clinical diagnostic laboratories, including newer technologies such as next-generation sequencing and digital droplet polymerase chain reaction, as well as their applications, are reviewed. Finally, we discuss considerations in designing a molecular test menu to deliver accurate and timely results in an efficient and cost-effective manner.

Cell-blocks and other ancillary studies (including molecular genetic tests and proteomics)

Many types of elective ancillary tests may be required to support the cytopathologic interpretations. Most of these tests can be performed on cell-blocks of different cytology specimens. The cell-block sections can be used for almost any special stains including various histochemistry stains and for special stains for different microorganisms including fungi, Pneumocystis jirovecii (carinii), and various organisms including acid-fast organisms similar to the surgical biopsy specimens. Similarly, in addition to immunochemistry, different molecular tests can be performed on cell-blocks. Molecular tests broadly can be divided into two main types Molecular genetic tests and Proteomics.

Ligation-Enabled Fluorescence-Coding PCR for High-Dimensional Fluorescence-Based Nucleic Acid Detection

Polymerase chain reaction (PCR) is by far the most commonly used method of nucleic acid amplification and has likewise been employed for a plethora of diagnostic purposes. Nonetheless, multiplexed PCR-based detection schemes have hitherto been largely limited by technical challenges associated with nonspecific interactions and other limitations inherent to traditional fluorescence-based assays. Here, we describe a novel strategy for multiplexed PCR-based analysis called Ligation-eNabled fluorescence-Coding PCR (LiNC PCR) that exponentially enhances the multiplexing capability of standard fluorescence-based PCR assays. The technique relies upon a simple, preliminary ligation reaction in which target DNA sequences are converted to PCR template molecules with distinct endpoint fluorescence signatures. Universal TaqMan probes are used to create target-specific multicolor fluorescence signals that can be readily decoded to identify amplified targets of interest. We demonstrate the LiNC PCR technique by implementing a two-color-based assay for detection of 10 ovarian cancer epigenetic biomarkers at analytical sensitivities as low as 60 template molecules with no detectable target cross-talk. Overall, LiNC PCR provides a simple and inexpensive method for achieving high-dimensional multiplexing that can be implemented in manifold molecular diagnostic applications.

Advances in diagnostic microfluidics

Microfluidics is an emerging field in diagnostics that allows for extremely precise fluid control and manipulation, enabling rapid and high-throughput sample processing in integrated micro-scale medical systems. These platforms are well-suited for both standard clinical settings and point-of-care applications. The unique features of microfluidics-based platforms make them attractive for early disease diagnosis and real-time monitoring of the disease and therapeutic efficacy. In this chapter, we will first provide a background on microfluidic fundamentals, microfluidic fabrication technologies, microfluidic reactors, and microfluidic total-analysis-systems. Next, we will move into a discussion on the clinical applications of existing and emerging microfluidic platforms for blood analysis, and for diagnosis and monitoring of cancer and infectious disease. Together, this chapter should elucidate the potential that microfluidic systems have in the development of effective diagnostic technologies through a review of existing technologies and promising directions.

Ambient ionization mass spectrometry imaging for disease diagnosis: Excitements and challenges

Tissue analysis in histology is extremely important and also considered to be a gold standard to diagnose and prognosticate several diseases including cancer. Intraoperative evaluation of surgical margin of tumor also relies on frozen section histopathology, which is time consuming, challenging and often subjective. Recent development in the ambient ionization mass spectrometry imaging (MSI) technique has enabled us to simultaneously visualize hundreds to thousands of molecules (ion images) in the biopsy specimen, which are strikingly different and more powerful than the single optical tissue image analysis in conventional histopathology. This paper will highlight the emergence of the desorption electrospray ionization MSI (DESI-MSI) technique, which is label-free, requires minimal or no sample preparation and operates under ambient conditions. DESI-MSI can record ion images of lipid/metabolite distributions on biopsy specimens, providing a wealth of diagnostic information based on differential distributions of these molecular species in healthy and unhealthy tissues. Remarkable success of this technology in rapidly evaluating the cancer margin intraoperatively with very high accuracy also promises to bring this imaging technique from bench to bedside.

Genomics research in Africa and its impact on global health: insights from African researchers

Africa may be heading for an era of genomics medicine. There are also expectations that genomics may play a role in reducing global health inequities. However, the near lack of genomics studies on African populations has led to concerns that genomics may widen, rather than close, the global health inequity gap. To prevent a possible genomics divide, the genomics 'revolution' has been extended to Africa. This is motivated, in part, by Africa's rich genetic diversity and high disease burden. What remains unclear, however, are the prospects of using genomics technology for healthcare in Africa. In this qualitative study, we explored the views of 17 genomics researchers in Africa on the prospects and challenges of genomics medicine in Africa. Interviewees were researchers in Africa who were involved in genomics research projects in Africa. Analysis of in-depth interviews suggest that genomics medicine may have an impact on disease surveillance, diagnosis, treatment and prevention. However, Africa's capacity for genomics medicine, current research priorities in genomics and the translation of research findings will be key defining factors impacting on the ability of genomics medicine to improve healthcare in Africa.

Risk for molecular contamination of tissue samples evaluated for targeted anti-cancer therapy

With the increasing usage of sensitive PCR technology for pharmacogenetics, cross contamination becomes a significant concern. Researchers employed techniques which basically include replacing laboratory equipment after each sample preparation; however, there are no recommended guidelines. In the present work we wanted to evaluate the risk of cross contamination during tissue processing using the routine precaution measures. Twenty-one surgical samples of lung adenocarcinoma were used, of which 7 contained EGFR exon 19 mutation, 7 contained EGFR exon 21 mutation (p.L858R) and 7 were EGFR wild-type. The samples were ordered by alternating the mutation group to maximize the potential for cross contamination and underwent tissue sectioning and de-paraffinization. The entire process was performed using the same tools. Following DNA extraction all samples underwent PCR amplification and were scrutinized for small fractions of EGFR mutation using deep sequencing with the Ion torrent PGM technology. Twenty samples yielded results. The fraction of mutated copies was 41 ± 23% (range 11–66) for the cases with known exon 19 mutation and 48±24% (range 0–65) for the cases with known exon 21 mutations. No in-frame exon 19 deletion mutations were identified in the wild-type (WT) and exon 21 groups. The fraction of EGFR exon 21 (codon 858) mutations was 0.018±0.014% (range 0–0.05%) in the WT and exon 19 groups, which was not statistically different than the background sequencing artifact noise for the same base-pair alteration (p = 0.21). Our results suggest that standard precautions are sufficient for molecular pathology diagnosis of surgical samples and are not associated with increased risk of cross contamination.

Pseudo-HE images derived from CARS/TPEF/SHG multimodal imaging in combination with Raman-spectroscopy as a pathological screening tool

Background

Due to the steadily increasing number of cancer patients worldwide the early diagnosis and treatment of cancer is a major field of research. The diagnosis of cancer is mostly performed by an experienced pathologist via the visual inspection of histo-pathological stained tissue sections. To save valuable time, low quality cryosections are frequently analyzed with diagnostic accuracies that are below those of high quality embedded tissue sections. Thus, alternative means have to be found that enable for fast and accurate diagnosis as the basis of following clinical decision making.

Methods

In this contribution we will show that the combination of the three label-free non-linear imaging modalities CARS (coherent anti-Stokes Raman-scattering), TPEF (two-photon excited autofluorescence) and SHG (second harmonic generation) yields information that can be translated into computational hematoxylin and eosin (HE) images by multivariate statistics. Thereby, a computational HE stain is generated resulting in pseudo-HE overview images that allow for identification of suspicious regions. The latter are analyzed further by Raman-spectroscopy retrieving the tissue’s molecular fingerprint.

Results

The results suggest that the combination of non-linear multimodal imaging and Raman-spectroscopy possesses the potential as a precise and fast tool in routine histopathology.

Conclusions

As the key advantage, both optical methods are non-invasive enabling for further pathological investigations of the same tissue section, e.g. a direct comparison with the current pathological gold-standard.

BreaKmer: detection of structural variation in targeted massively parallel sequencing data using kmers

Genomic structural variation (SV), a common hallmark of cancer, has important predictive and therapeutic implications. However, accurately detecting SV using high-throughput sequencing data remains challenging, especially for ‘targeted’ resequencing efforts. This is critically important in the clinical setting where targeted resequencing is frequently being applied to rapidly assess clinically actionable mutations in tumor biopsies in a cost-effective manner. We present BreaKmer, a novel approach that uses a ‘kmer’ strategy to assemble misaligned sequence reads for predicting insertions, deletions, inversions, tandem duplications and translocations at base-pair resolution in targeted resequencing data. Variants are predicted by realigning an assembled consensus sequence created from sequence reads that were abnormally aligned to the reference genome. Using targeted resequencing data from tumor specimens with orthogonally validated SV, non-tumor samples and whole-genome sequencing data, BreaKmer had a 97.4% overall sensitivity for known events and predicted 17 positively validated, novel variants. Relative to four publically available algorithms, BreaKmer detected SV with increased sensitivity and limited calls in non-tumor samples, key features for variant analysis of tumor specimens in both the clinical and research settings.