Demographic and clinico-pathological characteristics of colorectal cancer in Kirkuk governorate, Iraq

BACKGROUND

World-wide Colorectal cancer (CRC) is the third most common cancer with one million new cases a year. Historically, a higher incidence of this disease has been recorded among the elderly in the western countries, but it is increasing in developing countries and in younger age groups.

AIM

This study aims to find whether CRC cancer is progressively affecting the younger age groups known as early onset (< 50 years). In addition, it describes the pathological characteristics of CRC in early onset CRC cases.

METHOD

The study is retrospective cross-sectional. It was conducted over a period of five months from October 1st 2019 till 1st March 1st 2020. Data were drawn from patients with CRC from their medical records at Kirkuk Oncology Centre (KOC) and from the IRAQI National CANCER REGISTRY (INCR) over thirteen years period from 2006 to 2018. The basic data we obtained for each patient include sex, age, and stage, grade of the disease at diagnosis and mode of presentation.

RESULTS

The Initial study population included 654 patients of both genders and all ages. CRC occurred in < 5.5/100,000 population per year which accounted for < 8% of total malignancies (2006-2018). The patients were divided into two groups; an early onset (< 50 years) group and a late onset CRC (⩾ 50 years) group. The final study population provided enough data for 238 patients for the years (2014-2018) with an age range of 20-91 and a mean of 54.4 years. The males were ∼54% while ∼46% were females. The age group under 50 years (early onset CRC) was ∼41% (no 98) while those who are 50 years and older (late onset) stood for 59% (no 140). There were no statistical differences between the two age groups regarding stage, grade, or presenting symptom.

CONCLUSION

CRC is common in early onsets or young age groups with similar pathological characteristics to those of the late onset cancer. Accordingly, even mild lower gastrointestinal symptoms should be taken seriously. The study points toward an increasing awareness of the population on the importance of colorectal cancer. Also, conducting more surveillance studies and investigations would be recommended for early detections of the disease in young populations.

Trends in colorectal cancer in Iraq over two decades: incidence, mortality, topography and morphology

BACKGROUND

Colorectal cancer (CRC) is mainly a disease of the elderly in the Western world, but its characteristics are changing globally. Iraq does not have a well established CRC screening program. Understanding trends of CRC incidence, fatality and the clinical features of CRC patients is vital to the design of effective public health measures; public awareness, screening, diagnosis and treatment strategies to meet the future demands.

OBJECTIVES

Determine trends in demography, incidence proportion, mortality, topography (primary tumor site) and morphology (histology) over two decades.

DESIGN

Registry-based study SETTING: Iraqi National Cancer Registry (INCR) database PATIENTS AND METHODS: We collected and analyzed data from CRC patients obtained from the INCR to calculate incidence and mortality proportion per 100 000 population for the period from 2000 to 2019. In addition to estimation, data were examined by anatomic location and morphological type.

MAIN OUTCOME MEASURES

Change in the incidence and mortality proportion, topography and morphology of CRC over 20 years.

SAMPLE SIZE

20 880 CRC patients ranging in age from 14-80 years.

RESULTS

The overall (males and females) CRC incidence proportion (CIP) increased from 2.28 to 6.18 per 100 000 population in 2000 and 2019, respectively, with an annual percentage change (APC) of 5.11%. The incidence proportion (IP) of CRC in patients from 20 to <50 years rose from 1.46 in 2000 to 4.36 per 100 000 population in 2019, which is an APC of 5.6%. The IP in patients older than 50 years rose from 12.7 to 40.59 per 100 000 population in 2000 and 2019, respectively, with an APC of 5.98%. The percentage of all CRC cases to all total malignancies in Iraq grew from 3.69% in 2000 to 6.5% in 2019. The CRC mortality proportion increased from 1.25 to 1.77 per 100 000 populations in 2010 and 2019, respectively, reflecting an APC of 3.54%. Anatomically, colon (C18) tumor represented 59.2% and 65.7% in 2000 and 2019, respectively. Rectal (C20) tumors were 37.2% in 2000 down to 31.4% in 2019, while rectosigmoid junction tumor (C19) were 3.6% in 2000 dropping to 2% in 2019.

CONCLUSIONS

CRC in Iraq is still a disease of the elderly and is rising in incidence and mortality in all age groups. This necessitates reconsidering health policy regarding CRC; public awareness, screening and management strategies to accommodate for these alarming changes.

LIMITATIONS

Data about stages, grades and molecular characterisations are not available in the INCR.

CONFLICT OF INTEREST

None.

STAT3 paradoxically stimulates β-catenin expression but inhibits β-catenin function

Wnt signalling and the signal transducer and activator of transcription 3 (STAT3) are oncogenic signalling pathways which are deregulated in colorectal cancer (CRC). Here we investigated the interaction of these two pathways. Firstly, we investigated biochemical interaction by inhibiting STAT3 and β-catenin (through gene knock-down and dominant-negative TCF4 expression) in nine CRC cell lines. β-catenin inhibition did not affect STAT3 levels, whereas STAT3 knock-down resulted in reduced β-catenin mRNA and protein levels. The reduction in β-catenin protein was not prevented by proteasome inhibition, and IL6-induced STAT3 activation resulted in increased β-catenin mRNA. This suggests that STAT3 positively regulates β-catenin (at a transcriptional level) and evaluation of 44 CRCs by immunostaining supported this by showing an association between nuclear STAT3 expression and nuclear β-catenin (P = 0.022). We tested the functional interaction between STAT3 and Wnt signalling by knocking down STAT3 and β-catenin individually and in combination. Knock-down of β-catenin and STAT3 individually inhibited cell proliferation (P < 0. 001 for each) through G1 arrest. However, simultaneous knock-down of STAT3 and β-catenin had a significantly weaker effect than knock-down of β-catenin alone (P < 0.01). Knock-down of STAT3 and β-catenin, individually and together, inhibited cell motility (P < 0.001) without evidence of interaction. We conclude that STAT3 regulates β-catenin but β-catenin does not regulate STAT3. The STAT3/β-catenin interaction is complex but may reduce the proliferative activity of β-catenin possibly by taking β-catenin protein beyond the optimal level. This may indicate biological differences in tumours where both STAT3 and β-catenin are activated compared to those where only one is activated.

The utility of diagnostic biopsy specimens for predictive molecular testing in colorectal cancer

AIMS

If stratified medicine is to be applied in the neoadjuvant setting, predictive testing will have to be undertaken on preoperative diagnostic biopsy specimens. The aim of this study was to evaluate whether a diagnostic biopsy was adequately representative of the main tumour in colorectal cancer.

METHODS AND RESULTS

Thirty cases of paired biopsy and subsequent resection specimens were randomly selected. Samples were screened for mutation in KRAS (codons 12/13, 61, and 146), BRAF (codon 600 and exon 11), PIK3CA (exons 1, 9, and 20), TP53 (exons 5-8), and microsatellite instability, using the quick multiplex consensus or standard polymerase chain reaction (PCR) protocols followed by high-resolution melting analysis. A total of 570 paired PCR tests were performed for mutation detection, and identical results were obtained in both biopsy and resection specimens in 569 tests (>99% concordance). Four cases (13%) showed microsatellite instability, and, in all four cases, instability was seen at identical mononucleotide markers in both biopsy and matched resection specimens.

CONCLUSIONS

This is the first study to show that diagnostic biopsy specimens, even though they are a tiny sample of the tumour, are sufficiently representative for use in predictive testing for early driver mutations in colorectal cancer.

Cten is targeted by Kras signalling to regulate cell motility in the colon and pancreas

CTEN/TNS4 is an oncogene in colorectal cancer (CRC) which enhances cell motility although the mechanism of Cten regulation is unknown. We found an association between high Cten expression and KRAS/BRAF mutation in a series of CRC cell lines (p = 0.03) and hypothesised that Kras may regulate Cten. To test this, Kras was knocked-down (using small interfering (si)RNA) in CRC cell lines SW620 and DLD1 (high Cten expressors and mutant for KRAS). In each cell line, Kras knockdown was mirrored by down-regulation of Cten Since Kras signals through Braf, we tested the effect of Kras knockdown in CRC cell line Colo205 (which shows high Cten expression and is mutant for BRAF but wild type for KRAS). Cten levels were unaffected by Kras knockdown whilst Braf knockdown resulted in reduced Cten expression suggesting that Kras signals via Braf to regulate Cten. Quantification of Cten mRNA and protein analysis following proteasome inhibition suggested that regulation was of Cten transcription. Kras knockdown inhibited cell motility. To test whether this could be mediated through Cten, SW620 cells were co-transfected with Kras specific siRNAs and a Cten expression vector. Restoring Cten expression was able to restore cell motility despite Kras knockdown (transwell migration and wounding assay, p<0.001 for both). Since KRAS is mutated in many cancers, we investigated whether this relationship could be demonstrated in other tumour models. The experiments were repeated in the pancreatic cancer cell lines Colo357 & PSN-1(both high Cten expressors and mutant for KRAS). In both cell lines, Kras was shown to regulate Cten and forced expression of Cten was able to rescue loss of cell motility following Kras knockdown in PSN-1 (transwell migration assay, p<0.001). We conclude that, in the colon and pancreas, Cten is a downstream target of Kras and may be a mechanism through which Kras regulates of cell motility.

Incidence, case fatality and genotypes causing Clostridium difficile infections, Finland, 2008

Since 2000, the epidemiology of C. difficile infections (CDI) has changed in the US and Europe. Few population-based assessments of both incidence and case fatality of CDI have been performed. In this study, the Finnish nationwide laboratory-based surveillance data from the year 2008 were analysed to assess the incidence and case fatality of CDI, and to detect regional differences in relation to molecular epidemiology. A total of 6201 episodes of CDI were identified (118.3/100 000 population; range by regions, 57.2-189.1). The incidence increased by age and was highest in persons aged >84 years (1286.0). Of the CDI episodes, 711 (11.5%; range by regions, 2.2-15.0%) led to death within 30 days. The 30-day case fatality was highest (22.0%) in persons aged >84 years. In total, 334 (5% of all episodes) isolates from 13/21 regions were sent for genotyping: 120 (36%) were of PCR ribotype 027, and it was found in 6/13 regions. Among the rest of the isolates, 53 (16%) were of type 001, and 19 (6%) of 002 and 014. The incidence and case fatality were highest in elderly persons and varied regionally. This may be explained by uneven spread of hypervirulent PCR ribotypes, such as 027, but also differences in diagnostic activity or the patient populations among which the outbreaks are occurring.

Comparative analysis of pyrosequencing and QMC-PCR in conjunction with high resolution melting for KRAS/BRAF mutation detection

Mutation detection is important in cancer management. Several methods are available of which high resolution melting (HRM) analysis and pyrosequencing are the most versatile. We undertook a comparative analysis of these techniques. The methods are: To compare the limit of detection (LOD), mutations in KRAS (codon 12/13 hotspot) and BRAF (V600E hotspot) were tested. DNA mixtures containing mutant alleles at a frequency of around 25%/12.5%/6%/3%/ 1.5%/0.8% were analysed. To compare frequency of mutation detection, 22 DNA samples (nine high quality samples from cell lines, 13 low quality samples from formalin-fixed paraffin-embedded tissue) were tested for three hotspots in KRAS (codons 12/13, 61 and 146) and two hotspots in BRAF (V600E and exon 11). HRM analysis of KRAS (codon12/13) and BRAF (V600E) showed that 3% and 1.5% mutant alleles respectively could be reliably detected whilst pyrosequencing reliably detected 6% mutant alleles in each case. Of 110 tests performed on 22 DNA samples, in 109 cases HRM and pyrosequencing gave identical results. Two of the samples tested had previously been called as wild type for KRAS by direct Sanger sequencing but were found to be mutant by both HRM and pyrosequencing. Both HRM and pyrosequencing can detect small numbers of mutant alleles although HRM has a lower limit of detection. Both are suitable for use in mutation detection and are both more sensitive than Sanger sequencing.

Quick-multiplex-consensus (QMC)-PCR followed by high-resolution melting: a simple and robust method for mutation detection in formalin-fixed paraffin-embedded tissue

BACKGROUND

Mutation detection in tumours will become increasingly important in pathological diagnosis as 'predictive' mutations are identified. A cheap and reliable test that works on formalin-fixed paraffin-embedded (FFPE) tissue is required.

METHODS

The quick-multiplex-consensus (QMC)-PCR protocol was developed to be used with high-resolution melting (HRM) analysis. The assay was compared with Sanger sequencing. Robustness of the assay was tested in DNA from FFPE tissue.

RESULTS

QMC-PCR with HRM could detect a minimum of 2.5% of mutant alleles (compared with 20% detectable for Sanger sequencing). Ten mutation hotspots in KRAS, BRAF, PIK3CA and CDC4 were screened in 29 cell lines with 100% sensitivity and specificity. Forty-three FFPE colorectal tumours were sequenced for hotspots in KRAS and PIK3CA and then screened by QMC-PCR. There was 100% sensitivity, although, of 21 mutations detected by QMC-PCR, 16 were confirmed by sequencing (71% specificity, positive predictive value 76%). All 43 samples were then screened for mutations in all 10 hotspots. Of 430 tests, 43 (10%) showed aberrant melting and 36 were confirmed mutant (positive predictive value 84%). As our technique is more sensitive than direct sequencing, the remaining seven tests are probably sequencing false-negatives. Precision tests showed that there was little intra-assay and interassay variation.

CONCLUSIONS

QMC-PCR with HRM is a simple, robust and inexpensive technique which had greater sensitivity than Sanger sequencing. It allows multiple mutation hotspots to be rapidly screened and is thus highly suited to mutation detection in DNA derived from FFPE tissues.

Concomitant mutations and splice variants in KRAS and BRAF demonstrate complex perturbation of the Ras/Raf signalling pathway in advanced colorectal cancer

BACKGROUND AND AIMS

KRAS and BRAF mutations occur in colorectal cancers (CRCs) and are considered mutually exclusive methods of activating the RAS/RAF/MEK/ERK pathway. This pathway is a therapeutic target and KRAS mutation may predict tumour responsiveness. The purpose of this study was to investigate the relationship between KRAS and BRAF mutations in 24 CRC cell lines and 29 advanced CRCs.

METHODS

KRAS and BRAF mutations were detected using high resolution melting and sequencing. Expression of mutations was confirmed by reverse transcription- PCR (RT-PCR) and sequencing. CpG island methylator phenotype (CIMP) was tested by methylation-specific PCR.

RESULTS

KRAS or BRAF mutation occurred in 79% of cell lines and 59% of CRCs. In the cell lines, KRAS mutations occurred in 54% of cases (with 62% in codons 12/13 and 38% in other codons). Four cell lines had a homozygous mutation. Only heterozygous BRAF mutations were detected in 29% cell lines. The V600E mutation occurred most commonly and was associated with CIMP+ status (p = 0.005). Mutations at codons 529 and 581 were also found and, in one case, BRAF and KRAS mutation co-occurred. Unexpectedly, BRAF splice variants (with a predicted kinase-dead protein) were found in 5/24 (21%) cell lines. In advanced CRCs, KRAS mutations occurred in 48% of cases (64% codons 12/13, 36% other codons) and BRAF mutations in 10% (66% V600E, 33% exon 11). A compound KRAS/BRAF mutation was not seen.

CONCLUSIONS

Disrupted Ras/Raf signalling is common in CRC. Homozygous KRAS mutations and concomitant KRAS/BRAF mutations may be indicative of a gene dosage effect. The significance of BRAF splice variants is uncertain but may represent another layer of complexity. Finally, if KRAS mutation is to be used for predictive testing, then the whole gene may need to be screened as mutations occur outside codons 12/13.

Molecular characterization of methicillin-resistant Staphylococcus epidermidis strains from bacteraemic patients

In order to study the clonality of clinical methicillin-resistant Staphylococcus epidermidis (MRSE) strains and their staphylococcal cassette chromosome mec (SCCmec) elements, 60 isolates of MRSE from bacteraemic patients in three units of the Helsinki University Hospital, Finland were selected, covering the periods 1990-1993 and 1997-1998. The MRSE strains were analysed by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing and SCCmec typing. Eleven PFGE types (FIN-SE-1-11) with sequence type ST2 (clonal complex 2; CC2) were identified. The previously established methicillin-resistant Staphylococcus aureus SCCmec criteria were applied to name the MRSE SCCmec complexes, and it was found that 7% of the isolates carried SCCmec type IA (ccrA1, class B), whereas the majority (93%) yielded six non-typeable SCCmec PCR patterns (P1-P6). Within each SCCmec PCR pattern, two ccr recombinase genes (ccrA2 and ccrA3) and two mec gene complexes (class A and class B) were detected. In addition, the ccrC gene was associated with three of the six patterns. In conclusion, the MRSE strains were genetically related to each other (ST2) but their SCCmec complexes were unique combinations of elements previously recognized among SCCmec types III and IV.

Panton-Valentine leukocidin genes and staphylococcal chromosomal cassette mec types amongst Finnish community-acquired methicillin-resistant Staphylococcus aureus strains, 1997–1999

Methicillin-resistant Staphylococcus aureus (MRSA) strains from Finland covering years 1997-1999 were studied for the presence of Panton-Valentine leukocidin (PVL) gene loci, and the clinically well-defined community-acquired MRSA (CA-MRSA) strains (n = 108) also for staphylococcal chromosomal cassette mec (SCCmec) and multilocus sequence types (MLST). Only a minority (12%) of the CA-MRSA strains contained the PVL gene loci and possessed genotypes formerly described as typical to CA-MRSA strains. The majority of these strains were heterogenous by MLST and pulsed-field gel electrophoresis (PFGE) analysis but, however, harboured the SCCmec cassette type IV. In conclusion, it seems doubtful to consider only molecular characteristics such as the presence of PVL genes as definite markers for CA-MRSA strains.

Comparison of genotypes of methicillin-resistant and methicillin-sensitive Staphylococcus aureus in Finland

The frequency of horizontal transfer of the staphylococcal cassette chromosome mec to methicillin-susceptible Staphylococcus aureus is unknown. In order to gain more information regarding this frequency in Finland, the genotypes of 299 clinical methicillin-sensitive Staphylococcus aureus isolates were compared to representatives of 24 epidemic methicillin-resistant Staphylococcus aureus genotypes. Sixty-eight percent of the methicillin-sensitive isolates had a genotype similar to eight of the epidemic methicillin-resistant strains. The remaining isolates (32%) showed 22 different genotypes. The results indicate that, in Finland, several methicillin-sensitive Staphylococcus aureus genotypes may have acquired the staphylococcal cassette chromosome mec.