Concurrent Mutations in STK11 and KEAP1 Cause Treatment Resistance in KRAS Wild-type Non-small-cell Lung Cancer

Abstract

We herein report a patient with KRAS wild-type non-small-cell lung cancer (NSCLC) with concurrent STK11 and KEAP1 mutations. A 53-year-old man visited a local doctor with a complaint of left shoulder swelling and pain. He was diagnosed with NSCLC cT4N0M1c stage IVB. A comprehensive genome profile test revealed mutations in STK11 and KEAP1 but no KRAS mutations. The patient was refractory to radiotherapy, immunotherapy, and chemotherapy. Thus, STK11 and KEAP1 mutations can be considered resistance mutations that confer resistance to various anticancer therapies in KRAS wild-type NSCLC.

Introduction

The development of lung cancer treatment using immune checkpoint inhibitors (ICIs) and their combinations have increased the number of long-term survivors. However, some patients are resistant to treatments and experience rapid cancer progression, possibly due to treatment-resistant mutations.

Comprehensive genome profile (CGP) testing has enabled us to comprehensively screen for cancer-related gene mutations in patients with cancer, and studies on resistance mutations are vital as well. Serine/threonine kinase 11 (STK11) and kelch-like ECH-associated protein 1 (KEAP1) mutations are known to cause resistance to lung cancer therapy. Previous studies have reported that STK11 and/or KEAP1 mutations were enriched in men diagnosed at a young age who had a smoking history or a high tumor mutation burden (TMB) (1). Recently, it was reported that KRAS mutation-positive non-small-cell lung cancer (NSCLC) patients with the combination of STK11 and KEAP1 demonstrated resistance to treatment with various drugs (2-4).

We herein report a KRAS wild-type NSCLC patient with co-mutations of STK11/KEAP1 refractory to radiotherapy, combined immunotherapy, and chemotherapy.

Case Report

A 53-year-old man visited his local doctor with a complaint of left shoulder swelling and pain from the left shoulder to the left wrist joint since October 2020. Computed tomography (CT) revealed a mass in the right upper lobe of the lung and a large mass in the left scapula (Fig. 1A, C). A CT-guided needle biopsy was performed on the left scapular mass, and anaplastic non-small-cell carcinoma cells were detected (Fig. 2). A pathological evaluation revealed that the cells were negative for thyroid transcription factor-1 and p40. A blood test showed a high neutrophil/lymphocyte ratio (NLR) that was thought to have been caused by the STK11 mutation (5). Furthermore, multiple tumor markers were screened, including beta-human chorionic gonadotropin, but no trend implicating a specific histological subtype was observed (Table 1). Later, the patient was diagnosed with NSCLC cT4N0M1c stage IVB without any driver gene mutations showing 2% programmed death ligand-1 (PD-L1) expression. As the left scapular mass grew rapidly, accompanied by worsening pain, the patient was subjected to palliative irradiation (25 Gy/10 fr) starting in January 2021 prior to chemotherapy. However, both the left scapular mass and the right upper lobe lung mass grew eventually (Fig. 1B, D), with no improvement in his pain and a worsening of his general condition.

Figure 1.

Chest CT at the first visit depicting a 49×43-mm large mass in the upper lobe of the right lung (A) and a 76×60-mm metastatic bone mass with osteolytic changes in the left scapula (C). Two months later, the massed had grown to 80×45 mm (B) and 188×148 mm (D), respectively. CT: computed tomography

Figure 2.

Histopathological findings obtained by a CT-guided needle biopsy from the left scapula showed anaplastic non-small-cell carcinoma cells. CT: computed tomography

Table 1.

Laboratory Report on the First Visit.

Hematology			Biochemistry			Tumor Marker
WBC	13,550	/μL	TP	5.9	g/dL	CEA	12.4	ng/mL
Neut	86.8	％	ALB	1.8	g/dL	NSE	26	ng/mL
Ly	6.9	％	T-Bil	0.4	mg/dL	ProGRP	28.4	pg/mL
Mo	6.1	％	BUN	10.4	mg/dL	CYFRA	15.8	ng/mL
Eo	0.1	％	Cr	0.45	mg/dL	SCC	2.3	ng/mL
Ba	0.1	％	AST	38	IU/L	sIL-2R	956	U/mL
RBC	297	×104/μL	ALT	22	IU/L	β-hCG	670	mIU/mL
Hb	7.7	g/dL	LDH	573	IU/L	KL-6	1,168	U/mL
Ht	23.5	%	Na	132	mEq/L
MCV	79.1	fL	K	4.2	mEq/L
MCHC	32.8	%	Cl	94	mEq/L
Plt	59.9	×104/μL	Corrected Ca	10.3	mEq/L
			CRP	16.9	mg/dL

In February 2021, carboplatin+nab-paclitaxel+pembrolizumab therapy was administered at a low dose [carboplatin area under the curve (AUC) 4.5 on day 1; nab-paclitaxel 100 mg/m², on day 1, 8, and 15; and pembrolizumab 200 mg/body, on day 1 and every 4 weeks] because his performance status was 2 based on the Eastern Cooperative Oncology Group scale. In addition, the CGP test (FoundationOne^Ⓡ CDx Cancer Genome Profile Test), which is used in cancer genome medicine, was performed at the beginning of the treatment and identified STK11 and KEAP1 mutations, whereas KRAS was not detected (Table 2). Despite two treatment courses, however, his tumor grew, and his pain worsened. After a discussion with the patient, we decided to provide supportive care, and he died in April 2021.

Table 2.

Gene Mutations Detected in FoundationOne^® CDx.

APC N732fs*58

CUL3 splice site 1207-2A>T

KEAP1 G417W

MUTYH splice site 892-2A>G

RET R77H

STK11 STK11(NM_000455) rearrangement exon 1

TP53 R158L

Discussion

We herein report a patient with KRAS wild-type NSCLC treated for a STK11/KEAP1 mutation who proved refractory to radiotherapy, immunotherapy, and chemotherapy.

Among the multiple gene mutations detected by next generation sequence (NGS) in this case, STK11 and KEAP1 mutations are reported as treatment-resistant mutations in lung cancer therapy. STK11 is a tumor suppressor gene found in 8-39% of advanced NSCLC cases (6). It has been reported that PD-L1 expression decreases when tumor cells acquire the STK11 mutation (7-9), and the overall survival (OS) of NSCLC patients with STK11 mutations declines when they are treated with ICIs (7,8,10). Furthermore, STK11 mutations are known to be involved in radiotherapy resistance acquisition via the suppression of the KEAP1/Nrf2 pathway. In fact, in a previous study or patients with stage III NSCLC treated with radiotherapy, those harboring an STK11 mutation had a higher local recurrence rate and shorter OS than STK11 wild-type patients (11). In contrast, KEAP1 mutations are detected in 11-27% of patients with NSCLC (6). KEAP1 mutations are known to increase chemotherapy and radiotherapy resistance due to the decreased activity of the KEAP1/Nrf2 pathway (12,13). In addition, the KEAP1 mutation is reported to be a poor prognostic factor in patients with NSCLC (7,14).

These mutations are frequently reported as resistance mutations in lung cancer, particularly in patients with KRAS mutation-positive lung cancer. Skoulidis and Arbour report that patients with KRAS mutation-positive lung cancer have STK11 or KEAP1 mutations frequently and have a significantly shorter OS than those without these mutations (2,3).

As mentioned above, mutations in STK11 and KEAP1 can independently cause significant resistance to treatment. Furthermore, the coexistence of these mutations increases resistance to treatment and is associated with a poor prognosis (15-17). Shen et al. reported that the median OS of patients with co-mutations of STK11/KEAP1 in KRAS mutation-positive lung cancer was only 7.3 months (17). As both STK11 and KEAP1 are involved in the KEAP1/Nrf2 pathway, inter-communication may enhance Nrf2 activity, leading to therapy resistance (18).

Interestingly, our patient did not have any KRAS mutations. While STK11 and KEAP1 mutations have mainly been reported as factors associated with treatment resistance in KRAS mutation-positive patients, the frequency of coexistence of STK11 and KEAP1 mutations in patients with KRAS wild-type NSCLC was recently reported to be 3.9% (7). In addition, Wohlhieter et al. showed that the coexistence of STK11 and KEAP1 mutations causes resistance to various anticancer therapies, even in patients with KRAS wild-type lung cancer (18). Thus, we considered the coexistence of STK11 and KEAP1 mutations to be the crucial cause of treatment resistance development in this case. There are currently no effective treatments for lung cancer cases with these mutations. This highlights the need for the development of novel drugs that can selectively inhibit these genes.

Conclusions

This case report indicates that the combination of STK11 and KEAP1 mutations causes resistance to radiotherapy and combined immunotherapy and chemotherapy, even in patients with KRAS wild-type lung cancer. Thus, it should be emphasized that the presence of STK11 and KEAP1 co-mutations inflicts treatment resistance, regardless of the KRAS mutation status.

The authors state that they have no Conflict of Interest (COI).

Financial Support

This study was supported by JSPS KAKENHI (Grant Number 20K17182).